HOMA-IR is a calculation that combines your fasting glucose and your fasting insulin into a number that says something about your insulin sensitivity. You work it out with the formula HOMA-IR = (fasting glucose in mmol/l x fasting insulin in mIU/l) divided by 22.5. The higher the number, the more it can point to insulin resistance.
I often get asked how you actually arrive at that HOMA-IR and what a healthy number is. In this article I show you the formula, work through an example and explain which values are indicative. I am also honest about the limits, because HOMA-IR is a research measure and not a ready-made diagnosis.
Want the bigger picture first? Then read our pillar on insulin resistance in women and which blood values to test.
What is HOMA-IR?
HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It is a model that estimates how sensitive your body is to insulin, based on your fasting glucose and insulin. The model was developed in 1985 and is used mainly in research.
The idea behind it is simple. If your body needs a lot of insulin to keep your blood sugar normal, your cells respond less well to insulin. HOMA-IR captures that ratio between glucose and insulin in a single number.
So it is not a separate blood test, but a calculation based on two values you get from an ordinary fasting blood draw.
How do you calculate HOMA-IR?
You calculate HOMA-IR by multiplying your fasting glucose by your fasting insulin and dividing the result by 22.5. It is important to use glucose in mmol/l and insulin in mIU/l, because those are the units for which the constant 22.5 applies.
The table below shows the formula with a worked example and an indicative interpretation. Note: the cut-off values differ per lab and per population, so treat this as a guide and not a boundary.
| Part | Explanation or value |
|---|---|
| Formula | HOMA-IR = (fasting glucose in mmol/l x fasting insulin in mIU/l) / 22.5 |
| Example glucose | 5.0 mmol/l |
| Example insulin | 8 mIU/l |
| Calculation | (5.0 x 8) / 22.5 = 40 / 22.5 = 1.8 |
| Result | HOMA-IR of about 1.8 |
| Below 1 (indicative) | Low, usually favourable insulin sensitivity |
| About 1 to 2 (indicative) | Average, fits many healthy adults |
| Above 2.5 (indicative) | Possibly reduced insulin sensitivity, discuss with your doctor |
In the example above you arrive at a HOMA-IR of about 1.8. That falls in the average range and on its own does not point to a problem. The numbers in the table are indicative and meant to give you a feel, not to diagnose yourself.
Which HOMA-IR value points to insulin resistance?
There is no globally agreed cut-off value for HOMA-IR. Many studies use a value above about 2.5 as a signal of reduced insulin sensitivity, but that boundary differs per lab, per ethnicity and per age. A single value therefore says little without context.
What a healthy HOMA-IR is depends on the lab measurement method and the population in which the reference was set. So you cannot simply place two labs side by side.
See a raised result as a reason for a conversation with your GP, not as a fixed conclusion. Your symptoms, your weight, your family history and other values all count too.
Which blood values do you need?
For HOMA-IR you need two fasting values: your fasting glucose and your fasting insulin. Fasting means you eat or drink nothing but water for eight to twelve hours before the draw. That matters, because eating raises both your glucose and your insulin.
Your fasting glucose shows how much sugar is in your blood at that moment. Your fasting insulin shows how much insulin your pancreas needs to keep that sugar in balance.
Both values come from the same tube of blood taken in the morning. So you do not need a separate draw for it.
If you also want to map your long-term blood sugar, read what your HbA1c value says about your blood sugar over the long term.
What are the limits of HOMA-IR?
HOMA-IR is an estimate, not a direct measurement of insulin resistance. The gold standard for that is the clamp method, an intensive study procedure done only in research settings. HOMA-IR approximates that outcome, but with margins of error.
On top of that, the insulin measurement can vary a lot between labs. The same blood draw can give a different HOMA-IR at another lab. A single fasting value also varies from day to day.
HOMA-IR is less reliable in people who are already treated with insulin or whose pancreas makes little insulin. So see the model as a tool that gives direction, not as a stand-alone diagnostic test.
In short: HOMA-IR is a useful starting point, not an endpoint.
Having your own HOMA-IR determined
If you want your HOMA-IR calculated, you need a fasting glucose and fasting insulin. At Lunara you can do this without a referral with the Insulin Resistance HOMA-IR test, which draws both values and calculates the HOMA-IR for you.
If you want a broader look at your metabolism, a metabolic assessment also maps values like cholesterol and HbA1c. Every result is reviewed by a BIG-registered doctor.
In women, insulin resistance is often linked to PCOS. Read about that in PCOS and insulin resistance, the hidden cause.
Frequently asked questions
What is a normal HOMA-IR value?
A HOMA-IR around 1 is often seen as favourable and many healthy adults sit between about 1 and 2. Above 2.5 is considered possibly raised in many studies. The exact boundary differs per lab and population, so discuss your result with your doctor.
Do I have to be fasting for HOMA-IR?
Yes. Both your glucose and your insulin must be drawn fasting, so eight to twelve hours without food or sweetened drinks. Water is fine. Without fasting, HOMA-IR cannot be calculated reliably.
Is HOMA-IR a diagnosis for diabetes?
No. HOMA-IR is a research measure that gives an estimate of your insulin sensitivity, not a diagnosis. Your GP makes a diagnosis of diabetes or prediabetes based on your glucose and HbA1c, among other things, together with your symptoms and risk factors.
Can I calculate my HOMA-IR myself?
Yes, if you know your fasting glucose in mmol/l and your fasting insulin in mIU/l. Multiply both values and divide by 22.5. Make sure your lab uses the same units, otherwise the result will not be correct.
Why does my HOMA-IR differ per lab?
The insulin measurement is not standardised everywhere, so labs can give different values for the same blood. The references differ too. So preferably compare results from the same lab and discuss them with your doctor.
References
- Dutch College of General Practitioners (NHG). NHG Guideline Diabetes mellitus type 2. NHG, guidance on glucose and insulin resistance.
- Thuisarts.nl (in collaboration with the NHG). Information on blood sugar, diabetes and insulin resistance.
- Diabetes Fonds. Insulin resistance and prediabetes. Diabetes Fonds, public information.
- RIVM. Diabetes and risk factors in the Netherlands. National Institute for Public Health and the Environment.
Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. HOMA-IR is a calculation model and not a stand-alone diagnosis. For treatment decisions, discuss your results with your GP.
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