HbA1c is one of the most commonly ordered metabolic labs. It's useful, but it's an average — which means it hides patterns that matter and occasionally reports a number that misrepresents what your blood sugar is actually doing.
What HbA1c measures
Red blood cells pick up glucose from the bloodstream and hold onto it for the cell's lifespan (roughly 3 months). HbA1c measures the fraction of hemoglobin that has glucose attached — approximating your average blood sugar over that window.
What the numbers mean
Commonly cited cutoffs: under 5.7% is typically considered normal, 5.7–6.4% is often labeled prediabetes, and 6.5% or higher meets diabetes criteria. For most adults with type 2 diabetes, a target around 7% is widely cited, though targets are individualized (tighter for some, looser for older adults with multiple conditions).
Why trend matters more than any single reading
A single HbA1c is a blurry photograph of three months. Two values three months apart shows direction. Four values over a year shows whether a change in diet, exercise, or medication is actually doing anything. The absolute number without trajectory is much less informative than people assume.
What can move it — and what can mislead it
Diet, exercise, body fat, sleep, and medications all shift HbA1c. Less discussed: conditions affecting red blood cell turnover (anemia, hemoglobinopathies, recent blood loss or transfusion) can bias the value up or down. Fasting glucose, fasting insulin, and continuous glucose monitoring all add information HbA1c alone misses.
How VisitRecall tracks it
Every HbA1c on one trend line, alongside the fasting glucose and insulin drawn with it. See lab tracking and the longevity hub.
FAQ
How low should my HbA1c be?
That's a conversation with your clinician. "Optimal" for a longevity-oriented patient isn't the same as the treatment target for established diabetes.
Why might my CGM and HbA1c disagree?
Red blood cell biology, acute illness, or recent transfusion can bias HbA1c. If they disagree persistently, tell your doctor.
How often should I test?
Once or twice a year is common for asymptomatic adults; quarterly for active management of diabetes or recent medication changes.
