Why is my A1C high but my daily glucose readings are normal?

A high A1C with normal daily glucose readings usually means your blood sugar is rising at times you are not testing, such as after meals or overnight. Other possible causes include iron deficiency anemia, hemoglobin variants, or other conditions that affect how A1C is measured. A healthcare provider may recommend additional testing, such as a continuous glucose monitor (CGM), oral glucose tolerance test (OGTT), or iron studies, to identify the cause. [4] [5] [8]

Can stress and poor sleep raise my A1C?

Yes. Chronic stress increases cortisol levels, which can reduce insulin sensitivity and raise blood sugar over time. Inadequate sleep has also been shown to impair insulin sensitivity, making it more difficult for your body to regulate glucose effectively. Improving sleep quality and managing stress can support healthier long-term blood sugar control. [6] [7] [9]

Can iron deficiency cause a falsely high A1C?

Yes. Iron deficiency anemia can prolong the lifespan of red blood cells, allowing more glucose to attach to hemoglobin and resulting in an artificially elevated A1C. If your home glucose readings do not match your A1C, ask your healthcare provider whether iron studies or additional blood tests are appropriate. [4]

Should I use a CGM if my A1C doesn't match my glucose readings?

A continuous glucose monitor (CGM) can help identify hidden post-meal spikes, overnight glucose rises, and overall glucose variability that occasional finger-stick tests may miss. Even wearing a CGM for a short period can provide valuable information to help explain why your A1C is higher than expected. [8]