Abstract
Hemoglobin A1c (HbA1c) is a long-term measure for glucose concentration in plasma. Since its introduction as a diabetes monitoring tool, and its more recent application as a diagnostic tool, the number of measurements of HbA1c have risen dramatically. However, HbA1c change is slow, so repeating measurements should not be done too often. We use a large, unfiltered dataset from 52,017 patients to determine the possible rate of change in HbA1c concentration. In our laboratory, the critical difference between HbA1c measurements is 8.5%. Our data show that a 1-unit HbA1c rise takes 4 weeks to occur, hence, at a HbA1c concentration around 50 mmol/mol Hgb, a critically increased HbA1c concentration cannot be determined until after 16 weeks. Conversely a critically lower HbA1c can manifest itself after 2 weeks, but after 7 weeks the dropping tendency stops. The amount of measurements that can be cancelled because they were taken sooner than 16 weeks is 23 percent.
Disclosure statement
No potential conflict of interest was reported by the authors.