Insulin Sensitivity Calculator

This calculator computes three widely used surrogate markers of insulin resistance/sensitivity from a single fasting blood draw, plus a glucose-control estimate from HbA1c. HOMA-IR (Homeostatic Model Assessment of Insulin Resistance), introduced by Matthews et al. in 1985, multiplies fasting insulin (uU/mL) by fasting glucose (mg/dL) and divides by 405; higher values indicate more insulin resistance, with roughly under 1.0 considered optimal, 1.0-1.9 normal, 2.0-2.9 early resistance, and 3.0 or above significant resistance in commonly cited interpretive bands. HOMA-%B estimates pancreatic beta-cell function as a percentage, using the mg/dL-adapted form of the original formula: 360 times fasting insulin divided by (fasting glucose minus 63).

QUICKI (Quantitative Insulin Sensitivity Check Index), introduced by Katz and colleagues in a 2000 paper in the Journal of Clinical Endocrinology & Metabolism, is an alternative index built from the same two labs using logarithms instead of a raw ratio -- 1 divided by the sum of log10(insulin) and log10(glucose) -- which tends to have a more linear relationship with directly measured insulin sensitivity than HOMA-IR does, with values around 0.35-0.40 considered normal. Separately, the calculator converts HbA1c into an estimated average glucose (eAG) in mg/dL using the ADAG study's linear formula (28.7 x A1c - 46.7), a conversion clinicians use to translate a 3-month HbA1c percentage into a number that reads like a familiar glucose meter value. HOMA-IR, HOMA-%B, and QUICKI are surrogate indices validated against the euglycemic-hyperinsulinemic clamp (the gold-standard but impractical direct measurement) in research populations; none of them diagnose diabetes or insulin resistance on their own, and single fasting values can be affected by recent illness, medication, or non-fasting status.