What Is HOMA-IR?
HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It is the most widely used research index for estimating insulin resistance from a simple fasting blood draw. This guide explains what it measures, how it works, what the numbers mean, and its limitations.
What Does HOMA-IR Measure?
Insulin resistance means cells respond poorly to insulin — the pancreas must produce more insulin than normal to keep blood glucose in range. HOMA-IR quantifies this by looking at how much insulin is circulating relative to how high the fasting glucose is.
The logic: if your cells are sensitive to insulin, a small amount of insulin should be enough to keep fasting glucose normal. If insulin resistance is present, the pancreas compensates by secreting more insulin — so fasting insulin is elevated even when fasting glucose is still normal (or only mildly elevated).
The HOMA-IR Formula
Developed by Matthews et al. in 1985 at the University of Oxford. The constant 405 normalizes the result so that a healthy non-diabetic person scores approximately 1.0. For mmol/L glucose: divide by 22.5 instead of 405.
Example: Fasting glucose = 95 mg/dL · Fasting insulin = 12 µIU/mL
HOMA-IR = (95 × 12) ÷ 405 = 1140 ÷ 405 = 2.81 — borderline elevated.
Reference Ranges
| HOMA-IR | Interpretation |
|---|---|
| < 1.0 | Optimal sensitivity — low metabolic risk |
| 1.0 – 1.9 | Normal range for most healthy adults |
| 2.0 – 2.9 | Borderline — consider lifestyle review |
| 3.0 – 4.9 | Insulin resistance likely — discuss with provider |
| ≥ 5.0 | Significant resistance — clinical evaluation warranted |
Cut-off values vary in the literature (some use ≥ 2.5 as the resistance threshold). Population-specific norms differ by ethnicity, age, and BMI.
Limitations of HOMA-IR
- Not a diagnostic test. No single HOMA-IR value diagnoses diabetes or metabolic syndrome — it is a screening and research tool.
- Insulin assay variation. Fasting insulin values differ significantly between laboratories and assay methods. Results from different labs are not directly comparable.
- Requires true fasting. The sample must be from an 8–12 hour fast. Even a small meal alters both glucose and insulin levels dramatically.
- Less valid in insulin-deficient patients. Type 1 diabetes and advanced Type 2 (with beta-cell failure) will show low insulin regardless of glucose level — HOMA-IR loses interpretive value.
- Single time point. Insulin resistance fluctuates with stress, illness, activity, and sleep. One measurement is a snapshot, not a definitive assessment.
HOMA-IR vs Other Indices
| Index | Formula | Higher = More Resistant? | Best Use |
|---|---|---|---|
| HOMA-IR | (G × I) ÷ 405 | Yes | Most widely validated; best for population studies |
| QUICKI | 1 ÷ [log(I) + log(G)] | No (higher = more sensitive) | Better discrimination in normal sensitivity range |
| G:I Ratio | G ÷ I | No (lower = more resistant) | Simple; good for hyperinsulinemia screening |
| TG:HDL Ratio | TG ÷ HDL | Yes | Uses lipid panel; no insulin required |
Sources
- Matthews DR et al. "Homeostasis model assessment." Diabetologia. 1985;28:412–419.
- Katz A et al. "Quantitative insulin sensitivity check index." J Clin Endocrinol Metab. 2000;85:2402–2410.
Last reviewed: June 2025