The CPT code for A1c is 83036 when a laboratory runs the test. CPT 83037 applies when the analyzer holds FDA clearance as a home-use device. That part of the decision takes about four seconds.
Collecting on the claim takes longer. Look up the number and you’ll have the code and nothing else. You’ll lose money downstream on the diagnosis pairing and the testing interval. The QW modifier costs practices more, because it turns on a CLIA certificate most billers never check.
Our coders work the CPT code for A1c across primary care and endocrinology panels every week. Every rule below traces to a CMS document we name in the text, so your team can verify the source before you change a workflow.
The 30-Second Answer
Lab test: CPT 83036 covers a laboratory hemoglobin A1c test. The official descriptor reads “Hemoglobin; glycosylated (A1c).”
Home-cleared device: CPT 83037 covers an A1c performed on a device the FDA cleared for home use, run during a patient encounter with the physician present.
Medicare coverage: NCD 190.21 covers 83036 and 82985. CMS declined to add 83037 to that list in decision memo CAG-00373N.
Screening: Medicare has covered 83036 for diabetes screening with ICD-10 code Z13.1 since January 1, 2024, under MLN Matters MM13487, with no coinsurance or deductible.
Modifier: Practices running in-office A1c bill 83036QW on most analyzers, not 83037QW. Your CLIA certificate type decides the modifier.
The Two A1c Codes, Side by Side
Both codes report the same analyte. The device that ran the test decides which one goes on the claim. The 83036 CPT code description and the 83037 CPT code description below come straight from the AMA code set.
A1c CPT Code Descriptions
| CPT Code | Official Descriptor |
|---|---|
| 83036 | Hemoglobin; glycosylated (A1c) |
| 83037 | Hemoglobin; glycosylated (A1c) by device cleared by FDA for home use |
| 82985 | Glycated protein. The fructosamine alternative, also covered under NCD 190.21 |
| 85018 | Blood count; hemoglobin. Not an A1c code. Different analyte. |
Coders make two errors with these four codes. Some drop 85018 onto a diabetes panel and expect A1c payment, because the hemoglobin CPT code family looks interchangeable at a glance. Others reach for 83037 whenever the test runs in the office.
Both times, someone looked up the CPT code for A1c and skipped the descriptor. Keep the descriptors in front of your coding team. A payer auditing the claim compares the billed code against the descriptor, and what the practice meant to bill doesn’t enter that review.
CPT 82985 sits on the same Medicare covered list as the CPT code for hemoglobin A1c, and physicians order it when a hemoglobin variant makes the A1c result unreliable. CMS published both A1c descriptors in its CMS decision memo CAG-00373N, which is also where the 83037 confusion started.
What CPT 83036 Bills For
An A1c measures the share of hemoglobin in a patient’s blood that has glucose attached to it. Red cells live about 120 days, so the result reflects average glucose across the previous 60 to 90 days rather than one morning’s reading.
Physicians order the CPT code for A1c for a handful of clinical reasons, and each one maps to a different diagnosis code. The payer reads that mapping and decides whether the claim pays, which is why the order reason belongs in the note before the specimen leaves the room.
When Providers Order an A1c
- Diagnosing diabetes or prediabetes in a symptomatic patient
- Monitoring glycemic control in established diabetes
- Evaluating a therapy change after a medication adjustment
- Screening an asymptomatic patient who carries risk factors
That last reason runs on a separate set of Medicare rules, and we cover them further down. Coders searching the CPT code for HbA1c land on 83036 in almost every one of these scenarios.
Three entities can bill the CPT code for hgb A1c, and they don’t bill it the same way. A reference lab submits under its own CLIA number. A physician office laboratory submits from the practice’s own analyzer, and a hospital outpatient department bills on an institutional claim.
The billing entity decides the claim form, the CLIA number that goes on it, and whether QW belongs on the line. Procedure code 83036 carries no professional component, so there’s no interpretation to split out and no modifier 26 question to answer.
83036 vs 83037: What Decides the Code
The analyzer’s FDA clearance decides the code, and every argument about the CPT code for A1c in office settings comes back to that. If the device holds FDA 510(k) clearance as a home-use device, bill 83037. If it doesn’t, bill 83036.
The 83037 CPT code description says nothing about point of care, yet a widespread reading treats CPT 83037 as the point-of-care code. CMS documented the opposite in coding analysis CAG-00373N, quoting the AMA position that 83037 is not intended to report an A1c obtained in the patient’s home by the patient or family.
The AMA describes 83037 as rapid-result testing that helps the physician manage glycemic control while the physician is present with the patient. CMS adds a harder line in the same memo: Medicare doesn’t pay for glycosylated hemoglobin testing as a clinical laboratory test when the patient or a family member performs it.
That distinction costs money when practices get it backward. Bill 83037 to Medicare expecting national coverage protection and you’ll find the code was never on that covered list.
One more sentence from the memo settles the rest. CMS notes that 83036 does not specify the test location and does not preclude point of service testing. An in-office analyzer alone doesn’t move the claim to 83037.
The Rule in One Line
If the analyzer holds FDA 510(k) clearance as a home-use device, bill 83037. If it does not, bill 83036 regardless of where in the clinic the test runs.
Fingerstick trips people up on its own. A capillary draw doesn’t change the code. Coders searching the CPT code hemoglobin A1c fingerstick or the hemoglobin A1c fingerstick CPT code find 83036 in most POC A1c settings, because you code from the analyzer, and the collection method has no bearing on it.
Write the analyzer model and its FDA clearance category into the chart or the lab log. When a payer audits the code choice on a point of care hemoglobin A1c claim, the device record is the defense your coder needs. Your coder won’t reconstruct that record eighteen months later.
The QW Modifier and Your CLIA Certificate
QW tells the payer that a CLIA-waived facility performed the test. It carries no information about where the test happened, and it doesn’t attach by default. Your certificate decides it.
Three certificate situations cover almost every practice. Hold a Certificate of Waiver and run a waived analyzer, and you append QW. Hold a Certificate of Compliance or a Certificate of Accreditation, and you leave it off.
A reference lab billing under its own CLIA number skips QW, and the same CLIA certificate types govern every other lab code your practice submits.
The device list is where practices get surprised. CMS publishes which analyzers fall under which code on its CMS waived test list, and the market-leading in-office machines sit under 83036QW.
Which A1c Analyzers Bill 83036QW vs 83037QW
| Code and Modifier | Devices CMS Lists Under It |
|---|---|
| 83036QW | Siemens DCA Vantage, Siemens DCA 2000 and 2000+, Alere Afinion AS100 and AS101, PTS Diagnostics A1CNow+ Professional Use, Bayer A1CNow+ Professional Use |
| 83037QW | Devices FDA-cleared for home use only, including Bio-Rad Micromat II Prescription Home Use and Cholestech GDX Prescription Home Use |
Most practices running in-office A1c are on an 83036QW device. Reaching for 83037 on a DCA Vantage or an Afinion puts the wrong CPT code for A1c on the claim before the modifier question even comes up.
Coders search this a dozen different ways. The CPT code for HgbA1c, the HgA1c CPT code, and the CPT code for A1c test in office all resolve to the same two-code decision, followed by the same certificate question.
Commercial payers audit CLIA modifier accuracy on lab claims. Append QW while holding a Certificate of Compliance and you create a modifier conflict. Omit it while holding a Certificate of Waiver and you get the same denial from the other direction.
Check your certificate type at the start of each plan year and update the billing template that same week. That check takes ten minutes. A recoupment request covering eighteen months of 83036 CPT claims takes a quarter to work through, and payer-specific claim scrubbing catches the mismatch before the claim leaves the practice.
Certificate-to-modifier mismatches show up as a pattern rather than a single claim, because the same template runs on every A1c you submit. If your A1c denials cluster around modifiers, that pattern is worth pulling before the next plan year starts.
Which ICD-10 Codes Establish Medical Necessity for 83036
A CPT code for A1c without a supporting diagnosis is a denial waiting to post. NCD 190.21 runs three lists: codes Medicare covers, codes it denies, and a third bucket for anything appearing on neither.
Payer systems crosswalk your submitted diagnosis against the covered table before a human ever sees the claim. Submit a code outside that table and the claim denies on the first pass, and the patient’s actual clinical picture doesn’t enter that decision.
Coders searching the ICD-10 code for hemoglobin A1c, the dx code for hemoglobin A1c, or the ICD-10 codes for A1c are all after the same table. The 83036 covered diagnosis list below reflects the codes MACs accept in most jurisdictions.
Covered Diagnosis Codes for CPT 83036
| ICD-10 Code | Description | When It Applies |
|---|---|---|
| E10.x | Type 1 diabetes mellitus | Established Type 1, coded to full specificity |
| E11.x | Type 2 diabetes mellitus | Established Type 2, the most common pairing |
| E11.65 | Type 2 diabetes with hyperglycemia | Uncontrolled patient, supports a shorter interval |
| E13.x | Other specified diabetes mellitus | Secondary or post-procedural diabetes |
| R73.09 | Other abnormal glucose | The code the covered list carries, see the next section |
| R73.01 | Impaired fasting glucose | Abnormal fasting result, no diabetes diagnosis yet |
| Z13.1 | Encounter for screening for diabetes mellitus | Screening only, separate benefit and separate rules |
| O24.x | Diabetes in pregnancy | Gestational and pre-existing diabetes in pregnancy |
E11.65 carries more medical necessity weight than E11.9 for a patient whose control has slipped. The same logic runs through the whole E11 family, from E11.36 for diabetic cataract to E11.22 for diabetic chronic kidney disease. Coding to the manifestation costs your provider no extra documentation time, because the note already says what’s going on.
Anyone researching 83036 medical necessity or the CPT 83036 medical necessity ICD-10 pairing ends up in the same place: the covered list first, then the frequency rule.
Check the current covered list against your own MAC before you rewrite an order set. CMS updates the lists on a quarterly cycle, and the covered diagnosis for 83036 in one jurisdiction doesn’t always match another.
Most billers treat covered dx for 83036 as a static list they memorized years ago. The list has changed since then, and so has the way payers read specificity. One code pair in particular catches good coders, and that pair is next.
Why R73.03 Gets Denied and R73.09 Gets Paid
R73.03 is the correct ICD-10 code for prediabetes. It’s specific, it matches what the provider documented, and Medicare’s covered list for A1c testing doesn’t include it.
R73.09 sits on that list. The descriptor reads Other abnormal glucose. So your coder sits between the code that matches the chart and the code that matches the payer.
A practice moves to R73.03 because it’s more specific, then watches A1c claims start denying about six weeks later. Your biller sees the denials and doesn’t connect them to the code change. They look random on a remittance, and structured denial management services are how the pattern surfaces.
Code what the provider documented. Then check the current covered list for your MAC before you assume the more specific code will pay. When the chart supports both findings, the order you sequence them in decides whether the claim clears.
The reverse error costs money too. Your coder can’t assign R73.03 off a lab value. The physician has to write prediabetes in the note. Without that language, R73.09 is the correct assignment anyway, and a documentation query costs less than working the appeal.
Coders look this up all day. The R7303 diagnosis code, the ICD-10 code for prediabetes, and the code for borderline diabetes mellitus all resolve to R73.03. The lookup tools stop there, and you won’t find the covered-list answer in any of them.
Searching the diagnostic code for A1c or the diagnosis code for hgb A1c brings up the same family, and the same gap sits underneath it.
Diabetes isn’t the only place this happens. The same specificity-versus-coverage gap runs through thyroid panels, where E03.9 specificity denials follow an identical pattern across a different endocrine code set.
Screening vs. Monitoring: What Changed for A1c Coverage
Effective January 1, 2024, Medicare covers HbA1c for diabetes screening when you bill it with ICD-10 code Z13.1. CMS MLN Matters MM13487 added it alongside the fasting plasma glucose test, CPT 82947, and the glucose tolerance tests, CPT 82950 and 82951, already sitting on the screening benefit.
Five rules came with that change. Four of them affect the claim line rather than the chart, which is why practices that updated the diagnosis code alone still watched claims deny.
What the 2024 Screening Change Means for Your Claims
| Rule | What It Means Operationally |
|---|---|
| Diagnosis code | Screening coverage ties to Z13.1. A diabetes diagnosis code makes the encounter monitoring instead. |
| Frequency | No more than 2 screenings within the 12-month period following the most recent diabetes screening test. |
| Cost-sharing | Coinsurance and deductible do not apply to an A1c furnished as diabetes screening. |
| Line-item modifier | CMS Transmittal R12694CP directs that modifier TS be reported on the line item. |
| Prediabetes distinction | Medicare no longer varies screening frequency on a prior prediabetes diagnosis. CMS removed the definition from the screening regulatory text. |
The modifier row is the one most practices miss. CMS Transmittal R12694CP directs that modifier TS be reported on the line item for diabetes screening. Report the screening without it and you’ve submitted an incomplete claim line.
MM13487 carries a January 1, 2024 effective date and a later implementation date. Practices that coded it right inside that window still watched the claims deny. MACs don’t go back through their own files, so a practice that never asked for reprocessing left that money behind.
Draw one boundary and everything downstream follows it. A patient carrying E10.x, E11.x, or E13.x on the problem list isn’t a screening patient, and Z13.1 fails the coverage edit on that claim. The CPT code for A1c stays the same on both claims while the coverage pathway underneath it changes.
Providers asking whether Medicare covers the hemoglobin A1c test, or whether CPT 83036 is preventive, are asking about two benefits at once. Hemoglobin A1c Medicare coverage splits into a screening track and a monitoring track, and each track carries its own frequency rule.
The ICD-10 code for hemoglobin A1c screening is Z13.1. Coders also search the ICD-10 code for A1c screening and the Z131 diagnosis code, and all three land on the same entry.
The cost-sharing waiver matters at the front desk more than in the billing office. Coinsurance and deductible don’t apply to an A1c furnished as diabetes screening, so collecting a copay on that visit creates a refund you’ll process later.
Screening intent has to exist before the order goes out. Your front desk also needs the date of the patient’s last diabetes screening to apply the two-per-12-months rule, which makes this an eligibility verification workflow problem rather than a coding one.
Pull the screening history at scheduling rather than at check-in. A patient who had a screening A1c eleven months ago at another practice still counts against the rolling window, and your staff can only see that in the eligibility response.
Most screening A1c rides on a wellness encounter, which is where annual wellness visit coding and the screening benefit intersect. Get the encounter type right and the diagnosis code follows it.
How Often Medicare Pays for CPT 83036
Medicare treats the CPT code for A1c as medically necessary about every 3 months for a patient whose control holds steady. Glycated hemoglobin reflects glucose across a 4 to 8 week span, so a shorter interval returns the same clinical picture twice.
NCD 190.21 doesn’t stop at a flat cap. It carries diagnosis groups that authorize a shorter interval. Uncontrolled diabetes supports an additional test per 3-month period. A pregnant Type 1 patient supports monthly testing.
That group structure explains something billers find maddening. Two claims carrying the same CPT code and different diagnosis codes get different answers, because the payer routes each one into a different frequency group based on the diagnosis.
A1c Frequency Structure Under NCD 190.21
| Patient Situation | Typical Allowed Interval |
|---|---|
| Stable, controlled diabetes | About every 3 months |
| Uncontrolled diabetes or a recent regimen change | One additional test per 3-month period, per MAC policy |
| Pregnant Type 1 diabetic patient | Up to one test per month |
| Diabetes screening under Z13.1 | 2 screenings per 12 months, separate benefit |
Local Coverage Determinations refine the national structure. Palmetto GBA allows one additional HbA1c every 3 months for patients with uncontrolled blood glucose, up to 8 tests per year. That figure belongs to Palmetto, and your own MAC may land somewhere else.
Coders researching the 83036 LCD, the LCD 83036 entry, the 83036 NCD, or the NCD for 83036 are chasing two documents at once. Section 190.21 of the NCD manual sets the national frame, and the LCD adds jurisdiction detail on top of it.
Run the test shorter than the standard interval and medical necessity for 83036 rests on what the note says at that visit. A regimen change, a medication adjustment, a new diagnosis, or an intercurrent event such as post-surgical recovery or glucocorticoid therapy all qualify.
Repeating diabetes monitoring on every quarterly claim is what auditors look for and what fails review. The note has to name the clinical trigger, and copy-forward language reads as absent documentation to a reviewer.
Screening frequency and monitoring frequency run on separate rule sets. Mixing them is one of the more common sources of avoidable A1c denials, and it lands on the remittance as a frequency edit rather than a coding error.
What CPT 83036 Pays and Which Fee Schedule Sets It
Medicare pays 83036 under the Clinical Laboratory Fee Schedule rather than the Physician Fee Schedule. The code carries no work RVU component, so a PFS lookup returns nothing.
Billers who search the PFS and come up empty sometimes conclude the code isn’t payable. They pulled the wrong table. The 83036 CPT code has sat on the lab schedule since the CLFS took over lab pricing.
Under PAMA, Medicare sets most clinical diagnostic laboratory rates from the weighted median of private payer rates that laboratories report to CMS. Those rates update on a multi-year data cycle rather than through an annual conversion factor.
No phase-in payment reduction applied in 2026. From January 31, 2026 through 2028, payment for a test that isn’t an advanced diagnostic laboratory test can’t drop more than 15% per year against the prior year, per the CMS CLFS 2026 annual update. The reporting period that feeds future rates ran February 1 through April 30, 2026.
We don’t publish a dollar figure here on purpose. CLFS rates move on their own cycle, and a number that was right in January reads as an error twelve months later. Pull the current rate from the CMS lab fee schedule file before you quote it to a physician.
Contracted commercial rates for the a1c CPT code vary by contract and by region. A physician office laboratory and a reference lab hold different contracts for the same test, and you can’t read either one off the panel rate.
On a code this high in volume, a rate sitting below contract costs you money in small amounts across thousands of claims. Verify the contracted rate for the CPT code for A1c instead of assuming it tracks the panel.
Catching that gap across a payer mix is a reporting job rather than a billing job, and full revenue cycle management handles it better than a claims queue.
Billing A1c Alongside Other Diabetes Codes
83036 is a standalone analyte code. You can report it with other clinically indicated tests on the same date, and the constraint is documenting why the provider ordered both.
Providers asking what lab tests include A1c tend to be building a diabetic panel rather than ordering one test. The CPT code for A1c stays separate from the panel codes below, and each line needs its own medical necessity.
Common Same-Day Pairings With CPT 83036
| Paired Code | What It Covers | Billing Note |
|---|---|---|
| 82947 | Glucose, quantitative, blood | Separately reportable when both are clinically indicated and documented |
| 80048 | Basic metabolic panel | Includes a glucose measurement; document why A1c adds distinct information |
| 80053 | Comprehensive metabolic panel | Ordered to monitor renal and hepatic status in diabetic patients |
| 82985 | Glycated protein, fructosamine | Used when a hemoglobin variant makes A1c unreliable; document the indication |
| 99213 to 99215 | Office visit E/M | Not bundled with the lab code; E/M documentation must stand on its own |
| 36415 | Venipuncture | Separately reportable per CPT, though many payer policies bundle it with same-day lab codes |
The glucose CPT code family sits next to A1c on most diabetic orders. The 82947 CPT code description reads glucose, quantitative, blood, and CPT code 80048 wraps that same glucose measurement into a basic metabolic panel. Anyone searching the CPT code for type 2 diabetes is looking at ICD-10 E11.x rather than a procedure code.
You can trip on specimen collection too. CPT 36415 covers venipuncture and CPT 36416 covers a capillary stick, and Medicare treats the 36416 CPT code as bundled with no separate payment. Don’t report both for the same collection.
Most practices leave the nurse-visit opportunity on the table. A patient comes in for an A1c, a nurse takes vitals, compares the result against the care plan, and counsels the patient. That encounter may support 99211 under the incident-to rules.
Two things have to be true. The supervising physician has to be credentialed with the payer, and the note has to document more than a specimen draw. The 99211 co-billing rules cover both conditions, and missing either one denies the E/M line while the lab line pays.
Duplicate denials come from a different direction. When a reference laboratory bills Medicare for 83036 and your practice submits a claim for the same test on the same date, one of the two denies. Write down which entity submits when a reference lab is involved.
Diabetic patients arrive with more than one abnormal panel most of the time. The lipid panel frequency rules that govern same-day cholesterol testing follow a similar covered-diagnosis and interval structure, and both denials tend to show up on the same remittance.
Why A1c Claims Get Denied
A1c denials cluster into five patterns. Each one is preventable upstream, and each one arrives with a specific remittance code attached.
Read the code before you read the claim. The remittance tells you which of the five you’re looking at, and that answer decides whether your team corrects and resubmits or builds an appeal.
A1c Denial Codes and What Triggers Them
| Code | What It Means | Common A1c Trigger |
|---|---|---|
| CO-50 | Not deemed medically necessary | Diagnosis outside the covered list, or frequency exceeded without documentation |
| CO-16 | Claim lacks information needed for adjudication | Missing CLIA number, missing referring provider NPI, incomplete demographics |
| CO-151 | Information does not support this many services | Frequency limit exceeded on a monitoring claim |
| CO-11 | Diagnosis inconsistent with procedure | CPT-to-ICD linkage failure, often R73.03 against a covered-list edit |
| CO-97 | Payment included in another service | Bundling edit, most often on same-day specimen collection |
| N115 | Local Coverage Determination limitation | LCD non-compliance on the diagnosis or the interval |
Diagnosis Outside the Covered List
Payer systems crosswalk the submitted diagnosis against a coverage table without human review. Submit a code outside that table and it denies whatever the patient’s clinical picture looks like. Fix it at the order by surfacing the patient’s active diabetes codes when a provider selects A1c.
Frequency Exceeded Without Documentation
A fourth or fifth test in a rolling year denies at most MACs when the note doesn’t explain the shorter interval. The note has to name the clinical trigger by date, and a standing order won’t carry it.
Modifier Conflict
Append QW while holding a Certificate of Compliance and the claim hits a modifier mismatch. Omit QW while billing from a waived setting and you get the same outcome. Both invite a recoupment request rather than a single denial.
Screening Billed as Monitoring
Code a screening encounter with a diabetes diagnosis and you lose the screening benefit along with the cost-sharing waiver. Code a monitoring encounter with Z13.1 and the claim fails the coverage edit. The direction of the error changes the fix.
Duplicate Reference-Lab Claim
Two entities billing the same test on the same date produces a duplicate denial for one of them. Sorting out which entity owns the submission takes one conversation, and practices keep postponing it until the denials pile up.
Denial codes tell you where the break happened. CARC 11 and CARC 167 both point at a diagnosis-to-procedure linkage failure, and on A1c claims that traces back to the covered list in most cases.
Denials citing 83036 medical necessity or an 83036 LCD policy limitation both come back to the covered list and the interval.
A single A1c denial is a claim problem. The same denial across forty diabetic patients is a workflow problem, because the CPT code for A1c repeats on every panel your practice touches. Sort denials by payer and by code before you sort them by patient.
A1c denials arrive in batches on a diabetic panel. Categorizing them by remittance code turns a denial list into a pattern your team can fix upstream, and that categorization is the work our denial specialists do every day.
Appealing an A1c Denial
Sort the denial before you work it. A CPT code for A1c denial falls into one of two tracks. Data errors get corrected and resubmitted as a corrected claim, and clinical or policy judgments go into the appeal track.
CO-50 and CO-151 are clinical and policy denials, so they belong in the appeal track. CO-16 and CO-11 are data problems, so they belong in the corrected-claim track. Your biller can sort a whole queue in an afternoon once they’ve got that rule.
Medicare gives you 120 days from the initial determination to request a redetermination. An unfavorable redetermination opens a 180-day window for reconsideration through a Qualified Independent Contractor. Commercial windows run anywhere from 30 to 180 days depending on the contract.
Miss the deadline and the denial becomes permanent. That’s the reason aged A1c claims belong in a tracked queue stamped with the date the denial arrived, and aged AR follow-up is where your team enforces those deadlines instead of noticing them too late.
The ABN mechanic decides who pays when you expect a frequency denial. Get a signed Advance Beneficiary Notice before the service and the claim carries GA, which shifts financial responsibility to the patient.
Skip the ABN and the claim carries GZ, which means your practice absorbs the write-off. GY signals a statutorily excluded service and has no place on a medical necessity denial, though billers reach for it by mistake.
What an A1c Appeal Packet Contains
- The original claim with every CPT and ICD-10 code as submitted
- The signed ordering documentation from the treating provider
- The clinical note establishing why the interval was appropriate
- The prior A1c result the current test is measured against
- The specific NCD or LCD citation you are challenging
Payers reject appeals that argue clinical need and skip the policy citation. Name the document and the section you believe the payer misapplied. A CO-50 citing covered dx for 83036 needs that citation in the packet.
Reporting A1c Results With CPT Category II Codes
Category II codes report the result value rather than the test. They sit next to the CPT code for A1c on the claim, carry no reimbursement, and exist for quality measurement. Coders confuse them with the lab code all the time.
Someone asking for the CPT code for an A1c result wants one of these four codes rather than 83036. You report 83036 to show the test happened. You report the Category II code to record what it showed.
CPT Category II Codes for A1c Results
| Code | Most Recent HbA1c Level |
|---|---|
| 3044F | Less than 7.0% |
| 3051F | Greater than or equal to 7.0% and less than 8.0% |
| 3052F | Greater than or equal to 8.0% and less than or equal to 9.0% |
| 3046F | Greater than 9.0% |
CPT code 3044F gets looked up more than the rest, because a result under 7% is the one practices want on the record. Anyone searching the CPT code for A1c less than 7 is looking for 3044F.
Coders search these one descriptor at a time. Coders look up the 3044F CPT code description one day and the 3052F CPT code description the next, and CPT II codes for A1c covers the whole family.
Some Medicare Advantage plans require the Category II code alongside 83036 or 83037 and won’t reimburse the lab service without it. That turns a quality code into a payment condition. Check whether any plan in your mix carries that requirement before you treat these codes as optional.
3045F is the one to watch. It covered the 7.0 to 9.0 range before the code set split that band into 3051F and 3052F. Practices still submitting 3045F generate rejections their billing team writes off without asking why.
The quality side carries more weight here than the dollar side. The measure once called HBD is now Glycemic Status Assessment for Patients With Diabetes, or GSD. It uses 83036 and 83037 alongside the four Category II codes and the matching LOINC values.
3046F records a result above 9.0% and leaves the measure open. Report it anyway. The gap closes when the next result comes in under threshold.
Submit Category II codes at zero dollars on their own claim line. Some practice management systems reject a zero charge, and a penny on the line clears the edit without affecting the remittance.
LOINC 4548-4 is the value most labs report for hemoglobin A1c, and it travels with the result rather than the claim. Quality teams pulling GSD performance work from the LOINC feed rather than the CPT feed.
Medicaid and Commercial Payer Variance
Medicaid varies by state, and it varies inside states too. Coverage, frequency, and rate get set at the state level and again by the managed care organizations operating there. Some states mirror the CLFS rate and some publish their own fee schedule.
Verify before you assume Medicare rules carry over. A state that pays the CLFS rate on 83036 may still run a different covered-diagnosis list, and the state Medicaid billing rules govern both.
Commercial variance runs along the same lines. Diagnosis lists, frequency limits, modifier expectations, and CLIA documentation requirements all differ by plan. Some commercial payers have issued A1c-specific billing instructions asking for CLIA status and device documentation on the claim.
Build the payer rule into the scrubber instead of discovering it on a remittance. The HbA1c CPT code runs through every diabetic panel you submit, so one plan’s rule difference multiplies across hundreds of claims before anyone notices.
Track denials by payer and not only by code. A CPT for HbA1c denial that shows up on one plan and nowhere else points at a contract or policy issue, and you’ll miss it if you sort by code alone.
Ask your payer reps for the written policy at the plan year kickoff. A rule you can cite in an appeal is worth more than a rule someone remembers from a phone call.
A1c Billing Questions Providers Ask
What is the CPT code for an A1c test?
The CPT code for A1c is 83036 when a laboratory performs the test. CPT 83037 applies when the analyzer holds FDA clearance as a home-use device and the test runs during a patient encounter. Both report the same analyte, and the device decides which one goes on the claim. The A1c test CPT code doesn’t change based on the room the test happens in. CMS confirmed that 83036 does not preclude point of service testing, so check the analyzer’s FDA clearance category before your team assigns either code.
What is the difference between CPT 83036 and 83037?
The device decides it. CPT 83037 applies when the analyzer holds FDA 510(k) clearance as a home-use device. CPT 83036 covers everything else, including in-office point-of-care testing on a standard analyzer. Setting alone doesn’t move the claim to 83037. CMS documented in coding analysis CAG-00373N that 83036 does not specify a test location, and that 83037 is not intended to report an A1c the patient or a family member obtained at home. Most in-office machines bill under 83036.
Is CPT code 83036 covered by Medicare?
Yes. Medicare covers 83036 under NCD 190.21, Glycated Hemoglobin and Glycated Protein, when the claim carries a diagnosis from the covered list. The same NCD covers 82985 for glycated protein. CMS declined to add 83037 to that covered code list in decision memo CAG-00373N, so a 83037 claim doesn’t inherit the same national coverage. Coverage also depends on the interval. A test that clears the diagnosis edit can still deny on frequency when the note doesn’t support a shorter interval.
What diagnosis codes cover A1c testing for Medicare?
E10.x for Type 1 diabetes, E11.x for Type 2, and E13.x for other specified diabetes carry most A1c claims. R73.09 for other abnormal glucose and R73.01 for impaired fasting glucose cover the pre-diagnosis range. Z13.1 applies to screening encounters under a separate benefit. The covered dx for 83036 shifts on a quarterly cycle and by jurisdiction, so confirm the current list with your own MAC before rebuilding an order set. Coding to the manifestation, such as E11.65 for Type 2 with hyperglycemia, carries more weight than an unspecified code.
How often will Medicare pay for an A1c test?
About every 3 months for a patient with stable, controlled diabetes. NCD 190.21 authorizes a shorter interval through diagnosis groups: uncontrolled diabetes supports an additional test per 3-month period, and a pregnant Type 1 patient supports monthly testing. Palmetto GBA allows up to 8 tests per year for uncontrolled patients, though that figure is jurisdiction-specific. Screening runs on its own clock at no more than 2 screenings within the 12-month period following the most recent diabetes screening test. The note has to justify any shorter interval at the visit.
Does CPT 83036 require the QW modifier?
Not always. QW applies when a CLIA-waived facility performs the test on a waived analyzer. Hold a Certificate of Compliance or a Certificate of Accreditation and you leave QW off. A reference lab billing under its own CLIA number skips it as well. The 83036 CPT code and the QW modifier travel together more often than practices expect, because the market-leading in-office analyzers appear on the CMS waived test list under 83036QW rather than 83037QW. Confirm your certificate type before setting the billing template.
Is an A1c test covered by insurance?
Yes, on two separate tracks that follow different rules. Medicare has covered HbA1c for diabetes screening with ICD-10 code Z13.1 since January 1, 2024, and coinsurance and deductible don’t apply to a screening A1c. Monitoring an established diabetes diagnosis runs under NCD 190.21 with standard cost-sharing and a frequency limit tied to the diagnosis group. Commercial plans set their own diagnosis lists and frequency caps. The encounter type at the time of the order determines which track the claim follows.
Why was my A1c claim denied?
CO-50, CO-151 and CO-16 account for most A1c denials. CO-50 fires when the diagnosis sits outside the covered list or the frequency ran short without documentation. CO-151 fires on a frequency limit. CO-16 fires when the claim is missing the CLIA number, the referring provider NPI or other required data. CO-11 shows up when the diagnosis and procedure don’t line up, which on A1c claims often means R73.03 hitting a covered-list edit. Read the remittance code first, because it tells your team whether to correct and resubmit or to appeal.
What is the CPT code for an A1c result?
Two answers apply, depending on what you mean by result. The lab test itself reports under 83036 or 83037. The result value reports under CPT Category II codes: 3044F for a level under 7.0%, 3051F for 7.0% to under 8.0%, 3052F for 8.0% through 9.0%, and 3046F for a level above 9.0%. Category II codes carry no reimbursement and exist for quality measurement. Some Medicare Advantage plans require the Category II code alongside the lab code and won’t reimburse the lab service without it.
What is the reimbursement rate for CPT 83036?
Medicare pays 83036 from the Clinical Laboratory Fee Schedule rather than the Physician Fee Schedule, so the code carries no work RVU and a PFS lookup returns nothing. Under PAMA, CMS sets the rate from the weighted median of private payer rates that laboratories report, and those rates update on a multi-year cycle. No phase-in reduction applied in 2026, and from January 31, 2026 through 2028 payment can’t drop more than 15% per year against the prior year. Pull the current figure from the CMS lab fee schedule file rather than a secondary source.
Getting A1c Claims Paid the First Time
The code choice is the short part. Search CPT for A1c and you’ll land on 83036 in one click. The analyzer’s FDA clearance decides 83036 versus 83037, and your CLIA certificate type decides whether QW belongs on the line.
The money sits in the pairing and the interval. The diagnosis has to appear on the covered list. The interval has to match the patient’s frequency group, and the note has to say why on any test that runs short.
Screening and monitoring are separate benefits with separate rules, and mixing them is the newest source of avoidable denials on this code. The change took effect January 1, 2024, and practices are still submitting screening A1c without modifier TS.
The CPT code for A1c is one of the highest-volume codes on a primary care or endocrinology panel. A rule mismatch on a code like that repeats across hundreds of claims before it registers as a pattern.
If you want to see whether that pattern sits in your own data, our free revenue cycle analysis pulls A1c denials by payer and by remittance code. The report is yours either way, and you’re under no obligation.
