HOMA-IR calculator: insulin resistance from fasting glucose and insulin

HOMA-IR is a number calculated from two ordinary lab results: a fasting glucose and a fasting insulin. It estimates how hard your body has to work to keep blood sugar normal, which can drift for years before glucose or A1c leaves the normal range. Enter both values from the same blood draw below. Glucose can be in mg/dL or mmol/L, and insulin in µIU/mL or pmol/L.

What the numbers mean

HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It comes from a 1985 paper by David Matthews and colleagues that modeled how the liver, pancreas, and muscle balance glucose and insulin overnight. The formula is short:

• HOMA-IR = glucose (mmol/L) × insulin (µIU/mL) ÷ 22.5
• HOMA-IR = glucose (mg/dL) × insulin (µIU/mL) ÷ 405

The constant is chosen so a lean, healthy young adult in the original study scores about 1. A higher number means more insulin was needed to hold glucose where it was, which is what insulin resistance looks like in a fasting sample.

HOMA-B comes from the same paper and estimates how much insulin the pancreas is producing, as a percentage of that same reference adult. It is 20 × insulin ÷ (glucose in mmol/L − 3.5), so it isn’t defined when fasting glucose is 3.5 mmol/L (63 mg/dL) or lower.

QUICKI, the Quantitative Insulin Sensitivity Check Index, uses the same two inputs on a logarithmic scale. It runs the other way: a lower QUICKI means more insulin resistance. It is included because some reports and studies quote it instead of HOMA-IR.

Getting the inputs right

HOMA-IR is only as good as the two numbers that go into it, and insulin is the more fragile one.

• Fast properly. Both values assume an overnight fast, usually 8 to 12 hours with only water. Coffee with milk or a small snack raises insulin far more than it raises glucose, and the result will overstate insulin resistance.
• Use one blood draw. The formula pairs a glucose and an insulin from the same moment. A glucose from one week and an insulin from another don’t give a HOMA-IR.
• Check the insulin unit. Most US labs report insulin in µIU/mL, and many other labs use pmol/L. The calculator divides pmol/L by 6, the usual factor. A few labs use a slightly different factor, so match the unit to the one printed on your report.
• Skip it if you take insulin. The test can’t tell injected insulin from insulin your pancreas made, so HOMA-IR doesn’t mean the same thing for someone on insulin therapy.

Why there is no single normal cutoff

You will find HOMA-IR “normal ranges” quoted with confidence online, and they don’t agree. Two things are behind that.

First, insulin tests aren’t standardized the way glucose tests are. Different assays can report noticeably different insulin values for the same sample, which a working group on insulin standardization documented in 2009. A HOMA-IR from one lab isn’t directly comparable with one from another lab, even if both did everything right.

Second, studies set their cutoffs from their own populations. Some use a value around 2.5 as a rough line. Others take the 75th or 90th percentile of the people they studied, which gives a different number in each country, age group, and body-size mix. None of these cutoffs is a diagnosis. Prediabetes and diabetes are diagnosed from glucose and A1c, and there is no standard clinical test for insulin resistance itself.

The authors of the method made a similar point in a later review, Use and abuse of HOMA modeling. They describe HOMA as most useful for comparing groups and for following the same person over time, and less reliable as a single reading for one individual. The same review describes HOMA2, an updated version of the model that the University of Oxford publishes as a free calculator. HOMA2 handles a wider range of values and gives slightly different numbers from the original formula used here. Don’t mix the two in one history.

Track your own number over time

Because cutoffs vary and insulin assays differ, the most meaningful comparison is your HOMA-IR against your own earlier HOMA-IR, measured at the same lab. A value that climbs from 1.2 to 2.8 over three years says more than whether one reading lands on either side of 2.5. So does a value that falls after a change in diet, exercise, weight, or medication.

That works best when you keep each glucose and insulin pair together with its date and lab. Put A1c on the same timeline. It moves more slowly, and insulin often rises to hold glucose steady before A1c changes, so the two together show more than either alone. How to track your A1c over time covers that side, and How to track your lab results over time has the general method for any test.

Limitations

• One draw is noisy. Fasting insulin varies from day to day, so a single HOMA-IR can move noticeably with no real change. Look for a trend across several results.
• It’s an estimate. The reference method for insulin resistance is the clamp study, a research procedure. HOMA-IR agrees with it reasonably well across groups, less precisely for one person.
• It assumes a typical fasting state. Very low glucose, very high glucose, and treatment with insulin all take it outside the conditions it was built for.

Calculating HOMA-IR in HealthViewer

HealthViewer is a lab results tracker that runs on your own computer. It imports glucose and insulin from lab report PDFs, MyChart downloads, and direct connections to your health system, and converts insulin between µIU/mL and pmol/L and glucose between mg/dL and mmol/L when results arrive in different units.

To track HOMA-IR, create a derived test in Settings → Derived Tests with the expression A * B / 405, glucose as A and insulin as B, and a date window of 0 days so only a glucose and insulin from the same day are paired. That expression assumes most of your glucose results are in mg/dL and your insulin in µIU/mL. If your glucose is mostly in mmol/L, use A * B / 22.5 instead, and if your insulin is in pmol/L, divide by 6 as well. HealthViewer calculates it for every date where you have both, converting a result reported in the other unit, and you can chart it in Trends next to your A1c.

Everything stays in an encrypted file on your computer, with no account and no cloud service. Getting Started walks through the first import.

This calculator is for understanding your results, not for diagnosis. HOMA-IR cutoffs are not diagnostic criteria, and insulin values differ between labs. Talk to your clinician about what your results mean for you.