HOMA-IR

HOMA stands for homeostatic model assessment. The calculation represents an assumed feedback relationship between liver glucose output and pancreatic insulin secretion in the fasting state. Formula versions differ according to whether glucose is reported in millimoles per litre or milligrams per decilitre, and updated computer models may produce different outputs.

The index is indirect. It is not the same as a glucose-clamp procedure, and it depends on the accuracy and comparability of both input tests. Fasting duration, acute stress, recent activity, illness, glucose method, insulin assay, and units can alter the result or make cross-laboratory comparisons difficult.

Thresholds vary by population, laboratory, method, and purpose, so one universal cutoff should not be assumed. HOMA-IR also does not show glucose patterns after meals or across the day. HbA1c and continuous glucose monitoring describe other time windows, while fasting insulin remains one of the index's two raw inputs.

Because the formula multiplies or otherwise models measured inputs, analytic error in either value carries into the index. Extra decimal places do not remove that uncertainty. Serial comparisons are clearest when collection preparation and laboratory methods remain consistent.

The model assumes a relatively stable fasting relationship between glucose and insulin. If the specimen was collected outside a genuine fasting steady state, the calculated precision can look greater than the physiological conditions support.