What Is HOMA-IR, and What Does It Say About Insulin Resistance?

The homeostatic model assessment of insulin resistance (HOMA-IR) estimates how resistant your body is to insulin from two fasting blood tests: glucose and insulin. If your glucose is normal but it takes a lot of insulin to keep it there, your body is resisting insulin’s effect, often years before blood sugar rises. HOMA-IR puts a number on that. It’s useful in research and for following one person over time, but there’s no agreed cut-off for “insulin resistant”.

This article is general information, not medical advice.

How It’s Calculated

Matthews and colleagues introduced the model in 1985. The usual formula is:

HOMA-IR = fasting glucose (mmol/L) × fasting insulin (µU/mL) ÷ 22.5

or, with glucose in mg/dL, glucose × insulin ÷ 405. A value of 1 corresponds to the reference population the model was built on: young, lean, healthy adults. Higher values mean more insulin resistance.

For example, a fasting glucose of 5.0 mmol/L (90 mg/dL) and insulin of 10 µU/mL give a HOMA-IR of about 2.2.

Why There’s No Universal Cut-Off

• Insulin assays differ. Insulin isn’t measured in a standardised way across laboratories, so the same blood can give different insulin values, and so different HOMA-IR values, in different labs.
• Populations differ. Studies have proposed different thresholds depending on the population, age, and method.
• It’s an estimate. The model approximates what a clamp study, the reference method, would measure, and works best for comparing groups or following one person with the same lab.

Getting a Reliable Value

• Fast for at least 8 hours, and have glucose and insulin drawn at the same time.
• Use the same laboratory for later tests.
• Avoid testing during an acute illness, or after unusually hard exercise or a disrupted night, which can affect both.

Weight loss, physical activity, and sleep tend to improve insulin sensitivity, and a falling HOMA-IR over months can show it.

Following It in Kaizora

Homeostatic Model Assessment of Insulin Resistance (HOMA1) is derived on Labs by Matthews’ formula from a Fasting Plasma Glucose and a Fasting Insulin drawn together, so editing either result recalculates it. It’s the original HOMA1 model, not the computer-based HOMA2, which gives different values. No default reference range is set, since no guideline sets one.

The Short Version

• HOMA-IR estimates insulin resistance from fasting glucose and insulin.
• HOMA-IR = glucose (mmol/L) × insulin (µU/mL) ÷ 22.5.
• There’s no universal cut-off, since insulin assays and populations differ.
• Follow your own trend with the same lab.

Sources

• Matthews DR et al., “Homeostasis model assessment: insulin resistance and β-cell function from fasting plasma glucose and insulin concentrations in man,” Diabetologia 28, no. 7 (1985): 412–419. doi:10.1007/BF00280883
• Wallace TM, Levy JC, Matthews DR, “Use and abuse of HOMA modeling,” Diabetes Care 27, no. 6 (2004): 1487–1495. doi:10.2337/diacare.27.6.1487