HbA1c: your three-month sugar average
One number that summarizes ninety days of blood sugar — no fasting required. What it is, why it beats a single glucose reading, and what moves it.
PUBLISHED 2026-08-16 · UPDATED 2026-08-17 · 4 SOURCES
01How does one number average three months?
Glucose in the blood slowly glues itself to hemoglobin — the higher the average glucose, the larger the glycated fraction. Because a red blood cell lives roughly 120 days, the percentage reads out a three-month average nobody can cram for. That's why an international expert committee elevated the assay in 2009: it's steadier than any single fasting number [2].
It has known blind spots — conditions that change red-cell lifespan (some anemias, for instance) shift the number without shifting sugar. Another reason individual readings belong with a clinician.
02Why does A1c matter before anything is 'wrong'?
The ARIC study measured A1c in 11,092 adults without diabetes and followed them about fifteen years. Within the nondiabetic range, higher values were progressively associated with more cardiovascular disease and mortality — an association that held after adjusting for fasting glucose, while the reverse didn't [3].
Translation without drama: this is a dial, not a switch, and where you sit on the dial in your 30s and 40s keeps company with what your 60s look like. Dials respond to boring inputs applied for a long time — which is the entire thesis of this site.
03What is actually associated with moving it?
A JAMA meta-analysis of 47 trials found structured exercise associated with meaningfully lower A1c in people with type 2 diabetes — around 0.67 percentage points — with the largest associations above 150 minutes a week [4]. Notably, exercise *advice* alone showed little; structure did the work.
Muscle is the mechanistic reason to care as a lifter: it's the body's largest glucose sink, and training makes it a hungrier one through insulin-independent uptake during work. Every session is a deposit against this particular ledger, whatever your current number.
