What medications can cause false A1C levels?

October 17, 2025 •

4 min read

According to the CDC, A1C tests are crucial for monitoring long-term glucose control, but certain medications can interfere with results. Understanding what medications can cause false A1C levels is essential for ensuring accurate diabetes management and avoiding misinterpretation of your health status.

Quick Summary

This article outlines how certain medications and medical conditions can produce misleadingly high or low A1C results. It explains the underlying mechanisms, identifies common culprits, and emphasizes the importance of transparent communication with your healthcare provider for accurate diagnosis and monitoring.

Key Points

Red Blood Cell Lifespan Affects A1C: Some medications cause red blood cells to die faster (hemolysis), leading to a falsely low A1C reading that doesn't reflect actual blood sugar levels.
Assay Interference is a Factor: Certain substances, like high-dose aspirin or chronic opioid use, can interfere with the laboratory test itself, causing inaccurate results.
High-Dose Aspirin can Falsely Elevate A1C: Chronic, high-dose aspirin is known to cause falsely high A1C levels by interfering with some assay methods.
Medications That Cause Hemolysis Lead to Falsely Low A1C: Drugs such as dapsone, sulfasalazine, and some antiretrovirals can shorten red blood cell lifespan, artificially lowering the A1C result.
Some Drugs Raise Blood Sugar, Not a 'False' A1C: Systemic corticosteroids, statins, and beta-blockers raise actual blood glucose levels, resulting in an A1C that is accurately high, not falsely so.
Blood Disorders and Other Conditions Affect A1C: Conditions like anemia, kidney failure, liver disease, and genetic hemoglobin variants can also cause inaccurate A1C results.
Communicate with Your Doctor: Always inform your healthcare provider about all medications and supplements you take to ensure accurate interpretation of your A1C results.

The Importance of Accurate A1C Testing

The A1C test, or glycated hemoglobin test, is a common blood test that provides an average of your blood glucose levels over the past two to three months. Glucose in your bloodstream attaches to hemoglobin, a protein in red blood cells. The A1C test measures the percentage of hemoglobin with attached glucose. This metric is a cornerstone of diabetes diagnosis and management. However, the accuracy of this test can be compromised by various factors, including certain medications and health conditions. Misinterpreting an A1C result can lead to inappropriate treatment adjustments, potentially causing serious health risks, such as hypoglycemia (if the A1C is falsely low) or poorly managed hyperglycemia (if it's falsely high).

Mechanisms Behind Medication-Induced A1C Distortion

Medications can interfere with A1C results in two primary ways: by affecting the lifespan of red blood cells or by directly interfering with the laboratory assay used to measure A1C.

Altered Red Blood Cell Lifespan: Red blood cells typically live for about 120 days. If a medication shortens their lifespan (a process called hemolysis), the average age of red blood cells in your body is younger. Since there's less time for glucose to attach to hemoglobin, the A1C reading will be falsely low, even if blood sugar levels are high. Conversely, conditions that prolong the lifespan of red blood cells can lead to a falsely high A1C.
Assay Interference: Some drugs or substances can directly interfere with the chemical measurement process in the lab, causing an erroneous result regardless of blood sugar levels or red blood cell lifespan. Different A1C measurement methods (e.g., HPLC, immunoassay) have varying sensitivities to these interferences.

Medications That Cause Falsely Low A1C Levels

Drugs that induce hemolysis or affect erythropoiesis (red blood cell production) can cause a falsely low A1C.

Certain Antibiotics and Antimalarials: Drugs like dapsone, sulfasalazine, and trimethoprim-sulfamethoxazole can induce hemolysis, particularly in individuals with a genetic deficiency in glucose-6-phosphate dehydrogenase (G6PD). Ribavirin, used for hepatitis C, is also known to cause hemolysis and a falsely low A1C.
Antiretrovirals: Some medications used to treat HIV, such as nucleoside reverse transcriptase inhibitors, can lead to subclinical hemolysis and a lower A1C.
Other Medications and Supplements: High doses of antioxidant agents, specifically vitamins C and E, have been reported to lower A1C by reducing the glycation of hemoglobin, though the effect is not always significant at pharmacological doses.

Medications That Cause Falsely High A1C Levels

Some medications can create a falsely elevated A1C, suggesting a higher average blood sugar than is actually present.

High-Dose Aspirin: Chronic ingestion of very large doses of aspirin can acetylate hemoglobin, leading to falsely elevated A1C results due to interference with certain lab assays.
Chronic Opioid Use: Extended use of opioids has been linked to increased A1C levels, though the exact mechanism is not fully understood.
Alcohol: Chronic, heavy alcohol consumption can interfere with A1C results.
Immunosuppressants: Certain drugs used after organ transplantation, such as tacrolimus, can increase blood sugar and potentially impact A1C.

Comparison of Medication Effects on A1C


Medication/Class	Primary Effect on Blood Sugar	Impact on A1C Interpretation	Clinical Implication
Dapsone, Sulfasalazine	No direct effect on glucose	Falsely Low: Shortens red blood cell lifespan (hemolysis)	Requires alternative monitoring, like fructosamine or self-monitoring.
High-Dose Aspirin	Minimal direct effect	Falsely High: Interferes with some laboratory assays	Test may not reflect true glucose control, requiring careful interpretation.
Corticosteroids	Increases blood sugar	Accurately High: Elevated A1C reflects actual higher average blood glucose	Requires increased monitoring and potential diabetes medication adjustment.
Beta-blockers	Increases blood sugar (older types) and masks hypoglycemia symptoms	Accurately High: Elevated A1C reflects actual higher average blood glucose	Providers should choose newer beta-blockers or be aware of this effect.
Statins	Increases blood sugar slightly	Accurately High: Elevated A1C reflects actual higher average blood glucose	Benefits of statins usually outweigh the small risk of increased blood sugar.

Medications That Alter Blood Glucose (Not a “False” Reading)

It is important to distinguish between medications that cause a truly inaccurate A1C reading and those that affect blood sugar levels, leading to a genuinely higher or lower A1C. Many commonly prescribed drugs can raise or lower blood glucose and thus alter the A1C, even if the test itself is technically accurate.

Raising Blood Glucose: Corticosteroids like prednisone, statins for high cholesterol, thiazide diuretics, and atypical antipsychotics can all increase blood sugar levels. This effect can lead to a genuinely elevated A1C, not a false one.
Lowering Blood Glucose: Certain antibiotics like fluoroquinolones and some older pain relievers have been reported to cause low blood sugar, which could result in a lower A1C.

Conclusion: The Path to Accurate Glucose Assessment

Because so many medications can influence A1C results, it is vital to communicate openly and transparently with your healthcare provider about all drugs and supplements you are taking. If your A1C result seems inconsistent with your daily blood sugar monitoring, or if there's a sudden, unexplained change, it's worth discussing potential medication interference with your doctor. They may recommend alternative monitoring methods, such as a fructosamine test, or switch to a different A1C assay to get a more reliable picture of your glucose control. Ultimately, accurate diabetes management depends on a complete and honest assessment of all factors, including your medication regimen. Consulting an endocrinologist for complex cases or conflicting results is always recommended.

For more detailed information on a wide range of medications, consult trusted medical resources such as MedlinePlus.

Frequently Asked Questions

A false A1C reading is a technical error caused by a medication interfering with the test itself or affecting red blood cell lifespan. A high A1C caused by a medication, like a corticosteroid, is an accurate reflection of the drug's effect of increasing your actual blood sugar levels over time.

Yes, high doses of Vitamin C have been reported to potentially lower A1C by inhibiting the glycation process. However, the effect can depend on the specific laboratory assay used.

Anemia, including iron-deficiency anemia, can cause a falsely high A1C result. Conversely, hemolytic anemia (where red blood cells are destroyed too quickly) leads to a falsely low A1C because the average red blood cell lifespan is shortened.

Common medications that can increase blood sugar include systemic corticosteroids, statins, thiazide diuretics, and certain antipsychotics. Unlike a 'false' reading, the elevated A1C in these cases accurately reflects higher average glucose levels caused by the medication.

A fructosamine test can be used as an alternative. Fructosamine measures average blood glucose over a shorter period (typically 2-3 weeks) and is not affected by red blood cell lifespan or many assay interferences.

You might suspect an inaccurate A1C if there is a significant discrepancy between your A1C result and your daily blood glucose monitor readings. For instance, a low A1C despite high finger-prick blood sugar levels is a major red flag.

No, you should never stop taking a prescribed medication without first consulting your doctor. Many of these medications are critical for managing other serious health conditions. Your doctor can help you develop a strategy for accurate glucose monitoring while continuing your essential treatment.