By the time HbA1c crosses 5.7% and your PCP calls you "pre-diabetic," your fasting insulin has likely been elevated for 5-10 years. A normal HbA1c is the last metric to change; fasting insulin is one of the first. If you've been told "your blood sugar is fine," run this number before celebrating.
Why HbA1c misses early insulin resistance
HbA1c measures glycated hemoglobin - the average blood sugar over the prior 90 days. It only rises when fasting glucose has been spending meaningful time elevated. The body compensates for insulin resistance for years by pumping more insulin to keep glucose normal.
Fasting insulin under 5 uIU/mL is excellent. 5-9 is healthy in lean, active individuals. Above 10 is the early metabolic-flag zone, even if HbA1c reads 5.2% and fasting glucose reads 92 mg/dL. The compensation is doing exactly what it's supposed to - and silently aging your tissues while it does.
The Whitehall and ARIC studies show fasting insulin elevated 5-10 years before fasting glucose, and 7-15 years before A1c crosses pre-diabetic thresholds. Treating from A1c alone catches the disease late.
How HOMA-IR ties it together
HOMA-IR = (fasting insulin x fasting glucose) / 405. A unitless score of how much insulin your body needs to maintain normal glucose. Low number = sensitive; high number = resistant.
Targets: HOMA-IR under 1.0 is excellent. 1.0-1.9 is healthy. 2.0-2.9 is early insulin resistance. Above 3.0 is significant. Many people with HbA1c at 5.4% ("normal") have HOMA-IR over 2.5 - the metabolic engine is running hot, the warning light just hasn't lit.
HOMA-IR is the single most useful number to track metabolic trajectory in a normal-A1c, normal-weight, normal-lipid person. It often shifts in 8-12 weeks of work, before any other lab moves.
What drives fasting insulin up
Visceral fat (regardless of total body weight - lean PCOS, lean fatty liver, ectopic fat). Sleep under 6 hours/night for more than 1-2 weeks. Stress and chronic cortisol elevation. Continuous sitting (over 8 hours/day without breaks). Diets above ~250 g daily refined carbs without paired protein/fiber.
Genetic and ethnic predisposition: South Asian, East Asian, Hispanic, and Native American populations carry higher insulin resistance at lower body weight. The thresholds we use are designed to flag earlier in these groups.
Medications: corticosteroids, beta blockers, statins (mild effect), some psychiatric medications. Not reasons to stop the meds - reasons to monitor.
What moves it down
Resistance training 2-3x/week: improves muscle insulin sensitivity in 4-8 weeks. The most leveraged single intervention.
Sleep 7+ hours/night consistently: even 3-7 nights of restricted sleep raises HOMA-IR by 20-40% in healthy adults. Caffeine cutoff after 2 PM, room temperature 65-68°F, dark room.
Protein floor (0.7-1.0 g/lb lean mass), 25-35 g daily fiber, walking 8-10K steps/day, and removing liquid sugar (juice, sweetened coffee, soda) from the daily intake. None require medication. Most return HOMA-IR to under 2.0 in 12-16 weeks.
When lifestyle alone isn't enough: metformin 500-2000 mg/day under provider review. GLP-1 is on the table when BMI and metabolic criteria support it (and ApoB or lipid risk is also elevated).
What to do now
Run the Advanced lab panel - it includes fasting insulin, fasting glucose, HOMA-IR calculation, HbA1c, ApoB, and a lipid panel in one fasted draw. This is the metabolic floor we measure every member against.
If your HOMA-IR comes back over 2.0 even with normal A1c, take it seriously. Eight to twelve weeks of strength training, sleep, and protein/fiber moves the number meaningfully. Retest, and decide whether you need pharmaceutical help or whether the foundation is enough.