The Insulin Resistance Test: What to Ask For and How to Read It

By Tina Chagoury, Clinical Dietitian · 6 min read · 2026-09-27

A normal glucose result does not rule out insulin resistance. Here are the tests that do show it, how to read HOMA IR sensibly, and how to prepare.

Many women who come to me already suspect insulin resistance. The constant hunger, the afternoon cravings, the weight that settles around the middle and will not shift. Then they have a blood test, the glucose comes back normal, and they are told everything is fine.

Often, it simply was not measured. Here is what each test actually shows, what each one misses, and what to ask for.

Why glucose alone is not enough

Insulin resistance means your cells respond less well to insulin. To compensate, the pancreas produces more of it. For years, that extra insulin can keep your blood sugar in the normal range.

So glucose stays normal while insulin climbs. A test that only looks at glucose sees the result of the effort and misses the effort itself. By the time glucose rises, insulin resistance has usually been there for a long time.

That is the whole reason insulin needs to be measured directly. If you want the background first, I explain insulin resistance in women in plain terms.

The tests, one by one

Fasting glucose

The amount of sugar in your blood after an overnight fast. It is standard and useful, but it only describes that one morning, and it is often the last marker to change.

HbA1c

HbA1c reflects your average blood sugar over roughly the previous three months, because glucose attaches to red blood cells, which live for about that long. It is one of the tests doctors use to diagnose prediabetes and diabetes.

It does not measure insulin at all. It can also mislead in certain situations: iron deficiency anaemia, recent blood loss, pregnancy and some inherited haemoglobin variants can push it up or down.

Fasting insulin

This is the test most often left off a standard panel, and the one I most want to see. A raised fasting insulin with a normal fasting glucose is the classic early picture: the pancreas is working harder than it should to keep things looking normal.

Ask for it by name. It usually has to be requested specifically.

HOMA IR

HOMA IR is a calculation made from your fasting glucose and fasting insulin, taken from the same blood sample. It estimates how hard your body has to work to keep your fasting glucose where it is. The higher the number, the more likely insulin resistance is.

A few things matter when you read it:

• Laboratories set their own reference ranges. Insulin is measured with different methods in different labs, so a HOMA IR from one lab cannot be compared directly with one from another.
• No single number diagnoses insulin resistance on its own. The cut offs you see online are rough guides, and they vary between populations and labs.
• It is a snapshot. A bad night's sleep, an illness, a stressful week or a heavy late dinner can all nudge it.
• Read it alongside everything else: your waist, your symptoms, your cycle, your triglycerides and HDL cholesterol, and your family history.

Glucose tolerance test with insulin

In an oral glucose tolerance test you drink a measured glucose solution, and blood is taken at intervals over two hours. The standard version measures glucose only. Some doctors also measure insulin at the same time points, which shows how much insulin your body needs to handle that sugar and how quickly it settles. It is more demanding, and your doctor orders and interprets it, but it can reveal a problem fasting tests miss.

Supporting markers

High triglycerides with low HDL cholesterol often travel with insulin resistance. So can a fatty liver on ultrasound or raised liver enzymes, because the liver turns surplus glucose into fat. I explain that process in how fatty liver starts.

Why a normal HbA1c can hide insulin resistance

This is the pattern I explain most often. HbA1c tells you whether your blood sugar is already high on average. It tells you nothing about how much insulin it took to keep it there.

A woman can have a perfectly normal HbA1c and a high fasting insulin, because her pancreas is still winning. That is exactly the stage where changes to food, muscle and sleep work best, which is why it is worth catching.

What about a continuous glucose monitor?

A continuous glucose monitor does not diagnose insulin resistance. What it does is show you how your own blood sugar responds to your meals, sleep, stress and training in real life. I describe what I learned from wearing one in what a CGM teaches you.

How to prepare for the test

• Fast overnight, usually for 8 to 12 hours, with water only, unless your lab tells you otherwise.
• Test in the morning.
• Eat normally in the days before. A crash diet or a weekend of feasting just before the test skews the picture.
• Avoid unusually hard exercise the day before, and tell the lab if you slept badly or are unwell.
• Tell your doctor about your medicines and supplements. Some affect glucose, and biotin can interfere with certain lab tests, so ask whether to pause it.
• Keep copies of your results, and use the same lab when you retest.

What to do with the results

If your results suggest insulin resistance, your doctor decides whether medication is needed. For most women the foundations are the same either way: protein at every meal, fewer refined carbohydrates, no constant grazing, a walk after meals, strength training and enough sleep. I set these out in how to improve insulin sensitivity naturally.

Retest after three to six months with the same lab, so you are comparing like with like.

If your results are normal but your symptoms are strong, keep the conversation going. Unstable blood sugar, cortisol, thyroid function and iron can all produce similar symptoms.

When to see a doctor promptly

Constant thirst, passing urine often, blurred vision, unexplained weight loss or frequent infections can be signs of high blood sugar. Do not wait for a routine appointment. See a doctor soon and ask for your glucose to be checked.

This article is nutrition education, not medical advice. Blood tests should be ordered and interpreted with your own doctor.

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About the author. Tina Chagoury is a licensed clinical dietitian specialising in women's hormonal health, inflammation and gut health, and the creator of the Hormone Reset Method™. Learn more about the Hormone Reset Method.

Frequently asked questions

What is the best test for insulin resistance?

No single test is perfect. Fasting insulin and fasting glucose together, with HOMA IR calculated from them, alongside HbA1c and triglycerides, give a useful picture.

What is a normal HOMA IR?

Labs and studies use different ranges, and insulin is measured differently between labs. Read your result against your own lab's reference range, with your doctor.

Can I have insulin resistance with a normal HbA1c?

Yes. HbA1c shows average blood sugar and says nothing about insulin. A high fasting insulin with a normal HbA1c is a common early pattern.

Do I need to fast for an insulin test?

Yes. Usually 8 to 12 hours with water only, and the test is done in the morning. Follow your lab's instructions.

Is a glucose monitor enough to diagnose insulin resistance?

No. It shows how your blood sugar responds to daily life, but it does not measure insulin. Diagnosis needs blood tests.

Related reading

• Insulin Resistance in Women, Explained Simply
• Not Everyone With Insulin Resistance Needs Medication
• What Wearing a Continuous Glucose Monitor Taught Me About My Own Body