HOMA-IR Index: What It Shows, Normal Range and How to Calculate

When a doctor wants to know how well insulin is doing its job, they rarely look at a single value — more often at a pair. The HOMA-IR index is exactly that pair: it combines fasting glucose and insulin into one number used to judge insulin resistance. It is a cheap, widely used way to spot a metabolic problem before diabetes. Below: what HOMA-IR is, the formula, the normal range, how to take the test correctly and what to do if the index is high.

What the HOMA-IR index is

HOMA-IR (Homeostasis Model Assessment of Insulin Resistance) is a calculated index that estimates insulin resistance from fasting glucose and insulin. The model was introduced in 1985 and describes the balance between insulin production by the pancreas and its action on tissues. In plain words, HOMA-IR shows how much insulin the body has to keep in the blood to hold sugar steady: the more insulin needed at the same glucose, the less the cells "hear" it — that is insulin resistance.

The HOMA-IR formula and how to calculate it

The index uses a simple formula:

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

Both values come from a single fasting blood draw. The 22.5 is a normalising constant from the original model (the product of an "ideal" glucose of 4.5 mmol/L and insulin of 5 µU/mL). You do not have to do the maths by hand — enter your values into the HOMA-IR calculator and it returns the result and its interpretation.

HOMA-IR normal range and what the values mean

There is no single global cut-off — it depends on the lab, the insulin assay and the population. As a rough guide:

HOMA-IR is a guide, not a diagnosis. A doctor reads it together with HbA1c, lipids, waist circumference and symptoms. What a high index means and what to do about it — in detail in the article on insulin resistance.

How to take the test correctly

Preparation determines whether the result is reliable:

• Strictly fasting — 8–12 hours without food; water is fine.
• In the morning — glucose and insulin follow a daily rhythm.
• Both markers from one draw — glucose and insulin together, otherwise the index cannot be computed.
• The day before — no alcohol, heavy training or overeating; postpone the test during an acute illness.
• If you take medications affecting sugar or insulin, tell your doctor so they factor it into the interpretation.

What a high HOMA-IR means

A high index means the pancreas has to make more insulin to keep sugar normal. This is an early, still reversible stage on the way to prediabetes and type 2 diabetes, and it often comes with excess weight, high triglycerides and fatty liver. The good news: at this stage HOMA-IR genuinely drops within 2–3 months of lifestyle change — nutrition, movement, sleep and weight loss. Separately on what a high fasting insulin tells you.

Limitations of the index

HOMA-IR is convenient but not universal:

• It is designed for people without diabetes; in established diabetes and on insulin therapy its value falls.
• Insulin is measured by different assays, and lab results are not always comparable — it is best compared over time within one lab.
• Alternatives exist — QUICKI, HOMA2, triglyceride-based indices; they are used when the classic HOMA-IR is uninformative.

That is why a single index does not replace clinical assessment: it is useful as a screen and for monitoring trends.

When to test and which doctor

It makes sense to check HOMA-IR with excess weight (especially abdominal fat), sugar cravings and post-meal sleepiness, high triglycerides, PCOS, or when weight will not budge on a calorie deficit. Interpretation and management are handled by an endocrinologist or GP. To make sense of a finished report in plain language, use lab test decoding.

This information is for educational purposes and does not replace a specialist consultation.