An A1C test is covered by insurance under two main paths: a diabetes-related diagnosis code (types E08 through E13 in the ICD-10 system) or a preventive screening code (Z13.1) for people without a diagnosis but at elevated risk. Which path applies to you depends on whether you already have diabetes, have risk factors for it, or are being screened for the first time.
Screening Without a Diabetes Diagnosis
If you don’t have diabetes but your doctor wants to check your blood sugar levels, the A1C test can be billed as a preventive screening using the ICD-10 code Z13.1. As of January 2024, Medicare explicitly covers the A1C as a screening test under this code, and because the U.S. Preventive Services Task Force gave diabetes screening a Grade B recommendation, patient coinsurance and deductible do not apply. You pay nothing out of pocket for the test itself.
The USPSTF recommends screening for adults aged 35 to 70 who have a BMI of 25 or higher. Under the Affordable Care Act, most commercial insurance plans must cover Grade B preventive services with no cost sharing, so this same protection extends well beyond Medicare. If you’re in that age and weight range, your plan is generally required to cover A1C screening at no charge.
For Medicare specifically, screening is limited to no more than two tests within a 12-month period following your most recent screening test. The old rule that distinguished frequency limits based on whether you had prediabetes was eliminated in 2024, simplifying things considerably.
Diagnosed Diabetes: Type 1 and Type 2
Once you have a diabetes diagnosis, A1C testing shifts from “screening” to “disease management,” and a wide range of ICD-10 codes support coverage. The most commonly used codes fall into these categories:
- E11 (Type 2 diabetes mellitus): The most common diagnosis code used for A1C orders. Subcodes cover diabetes with complications like kidney disease (E11.21), retinopathy (E11.3x), neuropathy (E11.4x), or hyperglycemia (E11.65).
- E10 (Type 1 diabetes mellitus): Same structure as E11, with subcodes for specific complications.
- E08 (Diabetes due to an underlying condition): Covers diabetes caused by conditions like pancreatitis, cystic fibrosis, or Cushing syndrome. Subcodes include hyperosmolarity (E08.01), ketoacidosis (E08.10, E08.11), hyperglycemia (E08.65), and diabetic kidney or eye disease.
- E09 (Drug or chemical-induced diabetes): For diabetes triggered by medications like steroids.
- E13 (Other specified diabetes mellitus): A catch-all for rarer forms that don’t fit the other categories.
CMS policy is clear that A1C testing is “widely accepted as medically necessary for the management and control of diabetes.” It is also considered valuable for assessing hyperglycemia, a history of hyperglycemia, or dangerous hypoglycemia. The key distinction: these tests are covered for monitoring an existing condition, not for making an initial diagnosis.
Prediabetes and Elevated Blood Sugar
Prediabetes has its own ICD-10 code: R73.09. If your doctor has documented prediabetes or abnormal glucose findings, this code can support periodic A1C testing to monitor whether your blood sugar is progressing toward diabetes. The related code R73.01 covers impaired fasting glucose, and R73.02 covers impaired glucose tolerance, both of which may appear on your chart alongside or instead of prediabetes.
These codes sit in a middle ground. They’re not full diabetes diagnoses, but they document a real clinical finding that justifies ongoing monitoring. Your provider may also pair a risk-factor code (like obesity) with the screening code Z13.1 to strengthen the case for coverage.
Risk Factors That Support Coverage
Even without diabetes or prediabetes on your chart, certain conditions raise your diabetes risk enough that an A1C test may be covered as medically necessary. These include:
- Obesity (E66.x): A BMI of 30 or above is one of the strongest risk factors for type 2 diabetes and directly meets the USPSTF screening threshold.
- Overweight (E66.3): A BMI between 25 and 29.9, when combined with age 35 to 70, qualifies for covered screening.
- Polycystic ovary syndrome (E28.2): International guidelines recognize that women with PCOS have increased risk of impaired glucose tolerance and type 2 diabetes regardless of age and BMI. Guidelines recommend reassessing blood sugar every one to three years.
- Metabolic syndrome (E88.81): The cluster of high blood pressure, high blood sugar, excess abdominal fat, and abnormal cholesterol levels signals elevated diabetes risk.
These diagnoses don’t automatically trigger A1C coverage the way an E11 diabetes code does, but they establish the medical necessity that insurers look for when deciding whether to pay for the test.
Gestational Diabetes and Pregnancy
Gestational diabetes uses O-series codes in the ICD-10 system, primarily O24.4 for gestational diabetes mellitus. Women with pre-existing type 1 or type 2 diabetes who become pregnant are coded under O24.0 or O24.1 respectively. For pregnant patients with type 1 diabetes, A1C testing may be covered as often as once per month. For other pregnant patients with diabetes, testing more frequently than every three months requires documentation of medical necessity.
How Often Insurance Covers the Test
Coverage isn’t just about having the right diagnosis. Frequency matters too, and insurers will deny claims for tests ordered too close together.
For patients with stable, well-controlled diabetes (defined as two consecutive A1C results meeting treatment goals), two tests per year is the standard. This aligns with American Diabetes Association guidelines. If your diabetes is not well controlled, most insurers allow up to four tests per year, or one every three months. Some carriers, like Palmetto GBA (a major Medicare contractor), allow up to eight tests per year for patients with uncontrolled blood glucose, though anything beyond quarterly testing typically requires documentation showing why more frequent monitoring is needed.
For preventive screening under Z13.1, Medicare caps coverage at two tests in a 12-month window. Commercial plans generally follow similar limits, though specifics vary by insurer.
Why Claims Get Denied
The most common reason an A1C test isn’t covered is a mismatch between the diagnosis code and the purpose of the test. CMS explicitly states that A1C tests “are not considered to be medically necessary for the diagnosis of diabetes.” That means if your doctor orders the test purely to find out whether you have diabetes (rather than as a covered preventive screening or to manage known diabetes), the claim may be rejected unless it’s billed correctly as screening with Z13.1.
Other common denial triggers include testing more frequently than your diagnosis supports, using a vague or unspecified diagnosis code, or failing to include the required modifier. For Medicare diabetes screening specifically, claims historically required the “TS” modifier (indicating a follow-up screening service) for patients who met the definition of prediabetes, though the 2024 rule changes simplified some of these requirements.
If your A1C test was denied, ask your provider’s billing office which diagnosis code was submitted. In many cases, switching to a more specific or appropriate code and resubmitting the claim resolves the issue. Your provider can also submit an appeal with documentation of medical necessity if the standard codes don’t capture your situation.