Last updated: 2026-06-29

HOMA-IR

The HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) calculator estimates how resistant the body is to insulin from two routine fasting blood values: fasting plasma glucose and fasting insulin. It is used by clinicians and researchers as a simple, low-cost surrogate for insulin resistance — the condition in which cells respond poorly to insulin, forcing the pancreas to secrete more to keep blood glucose in range. Because it needs only a single fasting draw, HOMA-IR is far more practical than the clamp studies it approximates, which makes it one of the most cited metabolic indices in diabetes and metabolic-syndrome research.

What HOMA-IR measures

Insulin resistance sits upstream of type 2 diabetes, polycystic ovary syndrome, and several features of metabolic syndrome. In a healthy fasting state, a small amount of insulin holds glucose steady; when tissues resist insulin, the fasting insulin level rises even while glucose is still normal. HOMA-IR captures that imbalance by combining the two numbers into a single index. A low value reflects efficient insulin action; a high value reflects the high-insulin, normal-or-high-glucose pattern typical of resistance.

The formula

The original model, published by Matthews and colleagues in 1985, reduces to a single product divided by a constant:

where $\text{FPG}$ is fasting plasma glucose and $\text{FPI}$ is fasting insulin. The two constants are simply the same relationship in different glucose units: one millimole per litre of glucose is about 18 mg/dL, and $405 / 18 = 22.5$, so both forms give an identical result. Insulin is taken in µU/mL, which is numerically the same as mIU/L. This calculator accepts glucose in either unit and normalises internally, so the constant never has to be chosen by hand.

The denominator is not arbitrary: it is calibrated so that a normal-weight, fully insulin-sensitive young adult scores about 1. Values climb from there as resistance increases.

A worked example

Suppose a fasting panel returns a glucose of 102 mg/dL and an insulin of 12 µU/mL:

A score near 3.0 falls in the insulin-resistance range under the common international scheme, even though the glucose of 102 mg/dL is only marginally above normal. That is the value of the index: it flags the compensatory high insulin before fasting glucose itself becomes clearly abnormal.

Interpreting the score

There is no universal cut-off, because the result depends on the population studied and on the insulin assay used by the laboratory. A widely used international guide reads roughly: under 1.0 is insulin-sensitive, 1.0 to 1.9 is normal, 2.0 to 2.9 is borderline, and 3.0 or above indicates insulin resistance. Some populations use lower thresholds — Japanese guidance, for instance, treats 2.5 or above as resistance and 1.6 or below as normal. The most reliable comparison is always against the reference range printed by the laboratory that ran the test.

Two companion indices share the same inputs. HOMA-β estimates β-cell secretory function relative to a young-adult reference of 100%, which helps distinguish a pancreas that is compensating from one that is failing. QUICKI is an insulin-sensitivity index on a log scale, where lower numbers mean lower sensitivity. Reading the three together gives a fuller picture than any one alone.

Limits of the model

HOMA-IR assumes a working feedback loop between glucose and insulin secretion, so it loses meaning when that loop is broken — in people treated with injected insulin, or with type 1 or advanced type 2 diabetes where β-cell output is very low. It is also a fasting snapshot, sensitive to day-to-day variation in insulin and to differences between assays. A later, computer-based revision, HOMA2, recalibrates the model for modern assays and behaves non-linearly at the extremes, but its equations are available only through the official application. For a transparent, reproducible estimate from a standard fasting panel, the original HOMA-IR remains the standard, and it pairs naturally with the Triglyceride to HDL Ratio Calculator and Waist-to-Height Ratio Calculator as further markers of metabolic risk.