What Is HOMA-IR?
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — September 2026
By Ryan Mitchell · Referenced to Matthews et al. 1985 · Updated July 2026
HOMA-IR — the Homeostatic Model Assessment of Insulin Resistance — estimates how resistant your body is to insulin using just two fasting blood values: glucose and insulin. Introduced by Matthews and colleagues in 1985, it's one of the most widely used research and screening tools for insulin resistance because it needs no special test beyond a routine fasting draw. You may also see it written as the HOMA index, HOMA score, or simply HOMA — these all refer to the same calculation.
The HOMA-IR test: how it's ordered and done
There is no single "HOMA-IR blood test" you can request by name. HOMA-IR is a calculation derived from two ordinary lab results — fasting plasma glucose and fasting insulin — drawn from the same morning blood sample. Your clinician orders those two tests; the HOMA-IR score is worked out afterward from the numbers.
| Step | What happens |
|---|---|
| Fasting | 8–12 hours with water only — no food, caloric drinks, or coffee beforehand |
| Timing | Early-morning draw, before eating, heavy exercise, or the day's medications where advised |
| What's measured | Fasting plasma glucose (mg/dL or mmol/L) + fasting serum insulin (µIU/mL or pmol/L) |
| The result | HOMA-IR = (glucose × insulin) ÷ 405 — computed from the two values, not a separate assay |
| Turnaround | Same as a routine metabolic panel; the score is derived once both values return |
Because insulin assays are not standardized between laboratories, a HOMA-IR score is most reliable when tracked at the same lab over time rather than compared across providers. If your lab reports insulin in pmol/L, convert to µIU/mL (÷ 6.945) before using the 405 formula, or use our HOMA-IR calculator, which handles both unit systems.
The formula
Using glucose in mg/dL and insulin in µU/mL, the divisor is 405. If glucose is measured in mmol/L, the divisor is 22.5 instead. Example: glucose 95 mg/dL (5.3 mmol/L), insulin 12 µU/mL → (95 × 12) ÷ 405 = 2.8.
➜ Skip the arithmetic: HOMA-IR Calculator (supports both unit systems).
Normal range and interpretation
| HOMA-IR score | General interpretation* |
|---|---|
| < 1.0 | Optimal insulin sensitivity |
| 1.0 – 1.9 | Normal / early-optimal range |
| 2.0 – 2.9 | Emerging / possible insulin resistance |
| ≥ 2.9 | Significant insulin resistance likely |
*Cut-offs vary by lab, assay, and population — some studies use 2.5 or ethnicity-specific thresholds. Always interpret against your own lab's reference range.
Why it matters — PCOS, NAFLD, prediabetes
Insulin resistance sits upstream of many conditions, often years before blood glucose rises enough to flag on standard tests. A raised HOMA-IR is commonly seen in and used to monitor:
- Type 2 diabetes & prediabetes — resistance is the core defect long before diagnosis.
- PCOS — insulin resistance drives much of the hormonal picture; HOMA-IR is a common workup value.
- NAFLD / metabolic-associated fatty liver disease — closely tracks hepatic insulin resistance.
- Metabolic syndrome — resistance links the cluster of hypertension, dyslipidemia and central adiposity.
Because it catches the problem early, a rising HOMA-IR is often the trigger for lifestyle intervention — the window where diet, activity and weight change reverse resistance most effectively.
HOMA-IR vs HOMA2, HOMA-β and the other indices
The 1985 formula on this page is the HOMA1 model. In 1998 the same Oxford group published HOMA2 — a computer-based update that better handles higher glucose levels and different insulin assays; it must be run through the official HOMA2 calculator rather than by hand. For everyday screening the simple HOMA1 score is still the most widely quoted. A closely related output, HOMA-β (HOMA-B), uses the same two fasting values to estimate beta-cell function — how hard your pancreas is working — rather than resistance.
| Index | Measures | Notes |
|---|---|---|
| HOMA-IR (HOMA1) | Insulin resistance | Manual formula, ÷405 or ÷22.5 — this page |
| HOMA2-IR | Insulin resistance (refined) | Requires the official HOMA2 software model |
| HOMA-β / HOMA-B | Beta-cell function | Pancreatic output, not resistance |
| QUICKI | Insulin sensitivity | Log-transformed; more stable at low insulin |
| Triglyceride:HDL | Insulin resistance (surrogate) | Lipid-based, no insulin assay needed |
| Glucose:insulin ratio | Insulin resistance (screening) | Simplest fasting ratio |
Limitations
- Fasting only. Values must come from an 8–12 hour fast; non-fasting samples invalidate the result.
- Assay-dependent. Insulin assays aren't standardized, so scores aren't perfectly comparable between labs.
- Not for insulin-treated diabetes. Injected insulin makes the "fasting insulin" input meaningless.
- Single snapshot. One value can mislead; trends over time are more informative.
Frequently Asked Questions
What is a normal HOMA-IR?
Values under about 1.0 suggest optimal insulin sensitivity and roughly 1.0–1.9 is generally treated as normal in adults, with 2.0–2.9 borderline and 3.0 or above suggesting insulin resistance. No endocrine society has ratified a single universal cutoff, and thresholds shift with sex, ancestry and the insulin assay your lab uses.
Do I need to fast before a HOMA-IR test?
Yes. The calculation requires genuinely fasting glucose and insulin drawn from the same sample, normally after 8–12 hours with nothing but water. Anything with calories beforehand raises both inputs and inflates the score, making the result meaningless.
What is the difference between HOMA-IR and HOMA2?
HOMA-IR is the 1985 hand equation. HOMA2 is a later non-linear computer model that corrects for hepatic versus peripheral glucose resistance, the insulin secretion curve above 180 mg/dL (10.0 mmol/L), and circulating proinsulin, and it can run on C-peptide. Because the 1985 equation was calibrated to 1970s insulin assays, it tends to underestimate insulin sensitivity against modern lab results.
Can HOMA-IR be normal if I have insulin resistance?
Yes, and this is the score’s most important blind spot. HOMA-IR depends on how much insulin your pancreas is still producing. In longer-standing Type 2 diabetes, beta-cell output falls while resistance persists, so the score can drop even as the underlying problem worsens. A falling HOMA-IR alongside rising glucose is a warning sign, not progress.
Does a high HOMA-IR mean I have diabetes?
No. HOMA-IR is a screening estimate, not a diagnostic test, and no guideline uses it to diagnose anything. Diabetes and prediabetes are diagnosed from fasting glucose, HbA1c or an oral glucose tolerance test. A raised HOMA-IR is a reason to test properly, not a result to act on alone.
Sources & References
- Matthews DR, Hosker JP, Rudenski AS, et al. Homeostasis model assessment: insulin resistance and β-cell function from fasting plasma glucose and insulin. Diabetologia. 1985;28(7):412-9. Link
- Wallace TM, Levy JC, Matthews DR. Use and abuse of HOMA modeling. Diabetes Care. 2004;27(6):1487-95. Link
- NIDDK. Insulin Resistance & Prediabetes. Link
Written by Ryan Mitchell · Last updated: September 2026