When to Recheck A1C in Prediabetes
For individuals with prediabetes (A1C 5.7-6.4%), recheck A1C annually. 1, 2
Recommended Testing Frequency
Annual testing is the standard recommendation for all patients with prediabetes, as established by the American Diabetes Association. 1, 2
This yearly interval applies to individuals with A1C values between 5.7-6.4%, impaired fasting glucose (100-125 mg/dL), or impaired glucose tolerance (140-199 mg/dL on 2-hour oral glucose tolerance test). 1, 3
Special Populations Requiring More Frequent Monitoring
Women with prior gestational diabetes warrant more aggressive surveillance:
- These individuals should have lifelong testing at least every 3 years, though annual testing is reasonable given their elevated risk. 1, 2
- This population shows particularly strong response to metformin therapy, making early detection of progression especially important. 3
Clinical Context for Testing Intervals
The rationale for annual testing in prediabetes differs from established diabetes management:
In diagnosed diabetes, A1C is checked every 3 months when not at goal or therapy has changed, and every 6 months when stable and meeting targets. 4, 1
In prediabetes, the goal is surveillance for progression to diabetes, which occurs at approximately 10% per year in the U.S. population. 3
Annual intervals balance the need to detect progression early enough for intervention while avoiding excessive testing burden and cost. 1
Important Caveats About A1C-Based Prediabetes Diagnosis
A1C alone may miss substantial numbers of individuals with prediabetes:
Studies show that A1C testing alone (using the 5.7-6.4% range) misses 82-94% of individuals with glucose-defined prediabetes. 5
When screening identified only 412 individuals by A1C 5.7-6.4% criteria, it missed 1,270 (61%) of prediabetic individuals who would have been identified by combining impaired fasting glucose with A1C testing. 6
If initial A1C is in the prediabetes range but you have clinical suspicion for higher risk, consider confirming with fasting plasma glucose or oral glucose tolerance test, as these may identify additional individuals who would benefit from intervention. 5, 6
Conditions Affecting A1C Reliability
Be aware that A1C may not be reliable in conditions affecting red blood cell turnover:
- Pregnancy, sickle cell disease, recent blood loss or transfusion, hemodialysis, and erythropoietin therapy can all falsely alter A1C values. 1
- In these situations, use only plasma glucose criteria for diagnosis and monitoring. 1
Risk Stratification Considerations
While annual testing is standard, consider more frequent monitoring (potentially every 6 months) in individuals with:
- A1C values at the higher end of the prediabetes range (6.0-6.4%), as these individuals show substantially increased progression risk. 6
- Multiple additional risk factors including BMI ≥35, fasting glucose ≥110 mg/dL, or strong family history. 3
- Those who have declined or are non-adherent to lifestyle modification or metformin therapy. 3