Insulin resistance symptoms: why there often aren't any, and what the tests actually show

Georgina Waugh, Clinical Nutritionist (BHSc Nutritional Medicine) · 9 minute read · Updated 28 September 2026

Insulin resistance symptoms are hard to pin down for a simple reason: most of the time, there aren’t any you’d notice. What you might notice is the 3pm crash, the pull towards something sweet, and a waistband that changed while your eating didn’t. You mention it, the bloods come back “normal”, and you’re left wondering whether it’s just you.

It isn’t just you, and it isn’t a willpower problem.

Insulin resistance can sit underneath a normal blood sugar result for years, because your body works harder and harder to keep that number looking fine. So the test you had wasn’t wrong. It was answering a different question from the one you were asking.

The short version

• Insulin resistance usually has no symptoms of its own, and it’s most often a blood test that finds it.
• When your cells respond less to insulin, your body makes more, so your blood sugar can stay normal for years while insulin does the heavy lifting.
• In a study that followed 6,538 adults, the people who went on to develop diabetes had fasting glucose that barely moved for ten years, with insulin sensitivity about a third lower the whole time.
• Fasting glucose and HbA1c tell you where your blood sugar is. Fasting insulin, beside them, can point to how hard your body’s working to keep it there.
• It isn’t only about weight. Lean women with PCOS are insulin resistant too, and higher insulin in the late forties tracks with earlier hot flushes.
• In the biggest prevention trial, food and movement changes cut new cases of diabetes by 58%, more than the medication did.

What insulin resistance actually is

Insulin is the hormone that moves glucose out of your blood and into your muscles, liver and fat, where it’s used or stored. Insulin resistance means those cells don’t respond to insulin as well as they should.

So your pancreas makes more. And for a long time, that works.

Your blood sugar stays in range because your body is putting out extra insulin to hold it there. That’s the whole mechanism, and it’s why this one hides so well: the number most people get tested is the number your body’s working hardest to protect.

It tends to build slowly, and it’s more likely with a larger waist, age over 35 and a family history of diabetes, and with less movement, high triglycerides and high blood pressure.

Why insulin resistance symptoms are so hard to spot

Most of the time there are no symptoms at all. In Australia, 2 million people have pre-diabetes, the stage where glucose has started to creep, and it’s usually a blood test that finds it, not a symptom.

A few things can show up, and they’re worth knowing:

• a waist measurement over 80 cm, which is where the risk starts to rise for women
• darker, velvety skin in the folds of the neck, armpits or groin, called acanthosis nigricans, which is mostly linked to insulin resistance
• irregular periods, or being told you have PCOS. In an Australian study using the gold-standard clamp test, 75% of lean women with PCOS were insulin resistant, and 95% of those who were overweight
• hot flushes arriving early. In a US study that followed women through the menopause transition, higher fasting insulin at 47 predicted hot flushes starting younger and lasting longer

And the afternoon crash and the cravings? They get pinned on insulin all over the internet. They’re worth listening to, because your afternoon cravings often aren’t the problem, they’re the clue. But they aren’t specific. A small lunch, a short night and low iron can all produce the same 3pm.

Side note: weight is part of this story, and it isn’t the whole of it. That same PCOS study found insulin resistance in lean women, and in 62% of the overweight women who didn’t have PCOS. You can’t see it from the outside, in either direction.

What ten years of normal-looking results were hiding

The study I come back to on this is Whitehall II, which followed 6,538 British adults without diabetes. 505 of them went on to develop type 2 diabetes, and the researchers went back through up to 13 years of their blood results to see what had been happening before anyone knew.

Their fasting glucose barely moved. It averaged 5.47 mmol/L thirteen years out and 5.79 three years out. Only in the last three years did it climb, reaching 7.40 by the time diabetes was confirmed.

From the Whitehall II study: 505 people counted back from the day they were told they had type 2 diabetes, and the dotted line is the 6,033 who stayed well. The values are the study’s modelled averages.

Here’s the part that matters for you. Across that whole flat decade, their insulin sensitivity was about a third lower than in the people who stayed well, and their pancreas was already putting out around 10% more insulin.

Two honest caveats: 71% of them were men, and it’s an average, not a prediction about you. But that shape, a flat glucose line with a body working hard underneath it, is exactly why I don’t stop at blood sugar.

What the usual blood tests show, and what they can miss

There’s no routine blood test that hands you a label of insulin resistance, and the formal one is mostly a research tool. What you can ask for is a set of tests that each answer a slightly different question:

The test	What it shows	What it can miss
Fasting glucose	Your blood sugar at that moment, after a night without food	It can stay in range for years while your body makes more insulin to hold it there
HbA1c	Your average blood sugar over roughly the last three months	The same blind spot: it reports the sugar, not how hard your body worked for it
Oral glucose tolerance test	How your blood sugar handles a sugary drink over two hours	It’s usually ordered only once a fasting result or HbA1c has already come back raised
Fasting insulin, beside fasting glucose	How much insulin it takes to hold your glucose steady. The two can be combined into a score called HOMA-IR	There’s no agreed cut-off, and the line shifts with age in women, so it’s read with everything else, not as a pass or fail

That’s why I ask for fasting insulin beside fasting glucose and HbA1c. Not to label you from one number, but because the pair can point to how hard your body’s working to keep your glucose normal, which is the part the glucose alone can’t show you.

It needs reading with care. In a study of 2,459 adults, the HOMA-IR score that best flagged metabolic risk sat well below the usual top-10% line, and in women it shifted with age. So it sits beside your cycle, your waist, your family history and how you actually feel.

What I see in clinic. The pattern I see most often is a woman in her forties who arrives having done bloods with apparently “nothing found” and a long list of symptoms that she’s been told is due to “her age” or “stress”. When we go back and get new extensive bloods, HbA1c and fasting insulin are on that list, beside liver enzymes and a full thyroid panel including antibodies.

What the biggest prevention trial found

The Diabetes Prevention Program took 3,234 adults whose blood sugar was already raised and split them three ways: a placebo, the diabetes medicine metformin, or a food and movement plan aiming for 150 minutes of activity a week and about 7% weight loss.

The Diabetes Prevention Program followed 3,234 adults whose blood sugar was already raised, mean age 51, and 68% of them women, for about three years. These are trial averages, not a prediction for any one person.

That’s 58% fewer with the food and movement changes, and they beat the medicine.

I’m not quoting that to hand you a target weight. Most of what worked was ordinary: moving more and eating differently, consistently, with support.

Food’s the part I start with, and it’s rarely about cutting one thing out. It’s protein earlier in the day, meals that actually hold you until the next one, and enough protein for your stage of life.

Food is where I start, and it’s almost never about cutting one thing out.

What to do this week

1. Break up long stretches of sitting with a short, easy walk, especially after your biggest meal. In a pooled analysis of seven trials, light walking breaks lowered the glucose and insulin rise after a meal compared with staying seated, and did better than standing up. It’s free, and it’s the easiest thing on this list.
2. Measure your waist and write the number down. It’s a number for you and your GP, not a verdict on you, and nobody else ever needs to see it!
3. See your GP and ask for fasting glucose, HbA1c and fasting insulin, plus lipids and liver enzymes, alongside the basic foundations: full blood examination, iron studies including ferritin, B12, folate, a full thyroid panel with antibodies, vitamin D and zinc. Book the blood test for a morning so you can do it fasting.
4. If your cycle’s irregular, you’ve been told you have PCOS, or hot flushes have started earlier than you expected, say so in the same appointment. Your hormones are part of this picture.

When those results come back, the sentence most people hear is that everything’s normal. If that’s where you land, a Blood Test Analysis is fifteen minutes, one-on-one, going through the results you already have and showing you where your numbers are actually sitting, fasting insulin included. $79, no new test and no referral.

That’s the work, and it’s what we do. Your glucose, your insulin, your iron and thyroid, your cycle and what you actually eat, read together rather than one flag at a time.

And before you cut anything out, ask yourself:

• Has anyone looked at what my insulin is doing, or only my glucose?
• Did my waist change while my eating didn’t?
• Is my cycle, or perimenopause, part of this picture?
• Am I about to cut out a whole food group because of one reel?
• Who’s going to read my results with me, not just file them as normal?

None of this means something’s wrong with you. It means your body’s been doing a lot of quiet work, and it deserves someone looking at the whole picture. If weight and energy have been the conversation for a while, bring it to someone who’ll check the insulin as well as the sugar.

Bloods came back normal and you still don’t feel right?

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Common questions

How do you know if you are insulin resistant?

Usually not from symptoms. It tends to show up on blood tests: fasting glucose or HbA1c creeping up, or fasting insulin running high for the glucose it’s holding. Clues worth raising with your GP are a larger waist, darker velvety skin in body folds, PCOS or irregular cycles, and a family history of type 2 diabetes. No single number settles it; it’s read as a picture.

What are the symptoms of high insulin levels?

High insulin on its own usually doesn’t cause anything you’d notice. Where there are signs, they’re things like darker, velvety skin in the folds of the neck or armpits and, in women, irregular cycles linked to PCOS. Tiredness after meals and cravings get linked to it online, but they’re common for plenty of other reasons, so they’re a reason to check rather than an answer.

What are the causes of insulin resistance?

Usually several things adding up rather than one: more weight carried around the middle, less movement, age, and a family history of type 2 diabetes. In women, PCOS is strongly linked to it, including in women who aren’t carrying extra weight. That’s why the useful question is what’s contributing for you, not which single thing caused it.

How to improve insulin resistance?

Insulin sensitivity does respond to change, which is the good news. In the largest prevention trial, regular movement and eating differently cut new cases of diabetes by 58% in people already at high risk. What that looks like for you depends on your bloods, your stage of life and how you actually eat, so it’s worth working out with someone rather than copying a plan.

What foods should I avoid if I have insulin resistance?

There’s no single food to cut out, and cutting a whole food group isn’t where I’d start. What tends to matter more is the pattern: protein and fibre at each meal, fewer drinks and snacks that are mostly sugar, and meals that actually hold you until the next one. It’s worth building around your own results rather than a generic list.

Sources

Every study and number in this post comes from one of these.

1. Tabák AG and colleagues. Trajectories of glycaemia, insulin sensitivity, and insulin secretion… (Whitehall II). The Lancet, 2009.
2. Diabetes Prevention Program Research Group (Knowler WC and colleagues). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine, 2002.
3. Healthdirect. Pre-diabetes.
4. National Institute of Diabetes and Digestive and Kidney Diseases. Insulin resistance and prediabetes.
5. Stepto NK and colleagues. Women with polycystic ovary syndrome have intrinsic insulin resistance on euglycaemic-hyperinsulaemic clamp. Human Reproduction, 2013.
6. Athar F and colleagues. Insulin levels early in perimenopause inform vasomotor symptom incidence across the menopausal transition. Journal of Clinical Endocrinology and Metabolism, 2026.
7. Matthews DR and colleagues. Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia, 1985.
8. Gayoso-Diz P and colleagues. Insulin resistance (HOMA-IR) cut-off values and the metabolic syndrome in a general adult population: effect of gender and age. BMC Endocrine Disorders, 2013.
9. Buffey AJ and colleagues. The acute effects of interrupting prolonged sitting time in adults with standing and light-intensity walking on biomarkers of cardiometabolic health. Sports Medicine, 2022.
10. DermNet. Acanthosis nigricans.

Important: This article is general information written by a clinical nutritionist. It's not medical advice and doesn't replace care from your GP or another qualified health professional. Functional testing is not diagnostic and doesn't diagnose, treat, cure or prevent any condition, and results are best interpreted alongside your symptoms, history, medications and supplements.

Reviewed by Georgina Waugh

Clinical Nutritionist, BHSc Nutritional Medicine

Last updated: 28 September 2026

Sources reviewed: Healthdirect and NIDDK guidance, a 13-year cohort of 6,538 adults, a randomised trial of 3,234 adults, a clamp study in Australian women with and without PCOS, a menopause-transition cohort, a population study of HOMA-IR cut-offs, a meta-analysis of seven walking trials and DermNet.