Appropriate hemoglobin A1c testing frequency to monitor patients with type 2 diabetes

Background: Glycated hemoglobin (HbA1c) is used to monitor glycemic control among patients with type 2 diabetes (T2DM). HbA1c represents a 3-month glycemic average, with the most recent 6 weeks of glycemia having greatest influence. Analytical and biological variation introduce imprecision into any single HbA1c, where a result of 7.5% may represent a “true” value between 6.8% and 8.2%. Aims: This Therapeutics Letter evaluates the most appropriate interval for monitoring HbA1c in T2DM. Methods: Evidence was synthesized from a pragmatic randomized controlled trial (RCT) and three large observational studies. Results: In the RCT, 94% of patients monitored every 6 months maintained good glycemic control compared to 92% of those monitored every 3 months. Observational data indicated that 3-month testing resulted in a clinically unimportant difference in HbA1c compared with 6-month testing. Furthermore, patients tested 2 to 3 times annually were as likely to achieve personalized goals as those tested 4 times per year. Testing more than 4 times annually was associated with a lower probability of achieving targets. Conclusions: For patients with stable T2DM meeting glycemic goals, monitoring HbA1c every 6 months is as effective as every 3 months and could be contemplated for many patients following a discussion of patient goals and preferences. Frequent testing may be reserved for periods of medication adjustment, changes of health status, or when targets are unmet. Reducing testing frequency in stable patients minimizes low-value data, reduces the carbon footprint of lab testing, and improves patient convenience without compromising clinical outcomes.