Insulin resistance is not a diagnosis handed to you. It is a mechanism, describing how your body handles the hormone insulin: cells in muscle, fat and liver respond to it less well than they should, so the pancreas makes more to compensate.
And the thing worth knowing before anything else: there is no accepted clinical test for it. That is not a footnote. It explains a great deal of what you will read on this subject.
Why is there no "insulin resistance test"?
Because measuring it properly is a research procedure, not a clinical one. The US National Institutes of Health state that the test for insulin resistance is used primarily in research studies only, and that clinicians do not test for it directly.
The 2023 International PCOS Guideline is explicit: insulin resistance is a factor in the mechanism of the condition, "however, clinically available insulin assays are of limited clinical relevance and should not be used in routine care".
So if you are offered a fasting insulin test or an index calculated from one, the guidelines do not base a decision on it.
What is actually ordered instead
Glucose is measured, not insulin. These three tests are the accepted ones, and each has a range below diabetes called prediabetes.
| Test | What it measures | Prediabetes range |
|---|---|---|
| HbA1c | Average glucose over two to three months | 5.7% to 6.4% |
| Fasting glucose (FPG) | Glucose after an overnight fast | 100 to 125 mg/dL |
| Glucose tolerance (OGTT) | How the body handles a set dose of glucose | 140 to 199 mg/dL |
In PCOS specifically, the international guideline recommends the 75-gram oral glucose tolerance test as the most accurate way to assess glycaemic status — at diagnosis, then every one to three years depending on risk factors, and when planning a pregnancy. A lipid profile is taken at diagnosis, and blood pressure is measured annually.
What this has to do with your cycle
The connection is not direct; it runs through PCOS. Insulin resistance is one of the factors in its mechanism, and PCOS in turn is among the commonest reasons cycles space out and lose their regularity.
So if your cycles are persistently irregular — shorter than 21 days or longer than 35, or fewer than eight periods a year — the right path is not to hunt for an insulin test but to be assessed for PCOS by a doctor.
And if your cycles are regular, then cycle irregularity is not your route into this subject, and assessing glucose stays a general-health matter to raise with a family doctor.
What is worth asking your doctor
- Are my cycles persistently irregular?Shorter than 21 days or longer than 35, or fewer than eight periods a year.
- Are there other signs with it?More hair growth, persistent acne, or weight change.
- Is there type 2 diabetes in the family?Or gestational diabetes in your own history.
The short of it is that insulin resistance names a mechanism, not a test you can request. And if what brought you here was your cycle, the shorter route is a PCOS assessment rather than a number to chase.