Fasting Insulin and HOMA-IR: Tests That Show Insulin Resistance
Standard glucose tests can look normal for years while insulin resistance develops. The tests that show it earlier, and how to ask.
The tests you're routinely given measure glucose. Insulin resistance is a problem with insulin, and it can be well established while glucose still looks fine — because insulin is rising to keep it that way.
What the standard tests show
Fasting glucose. A single morning snapshot. Rises relatively late in the process.
A1C. A 90-day average. More informative than a single reading, and still a glucose measure.
Oral glucose tolerance test. You drink a standard glucose load and readings are taken over two hours. More sensitive than fasting glucose and better at catching impaired tolerance early — but less commonly done because it's time-consuming.
All three measure the outcome. None measures the effort your body is making to produce it.
The tests that show insulin
Fasting insulin. Straightforward, cheap, and rarely ordered by default. A high fasting insulin with normal glucose is the picture of compensated insulin resistance — your pancreas is working hard and succeeding, for now.
HOMA-IR. A calculation combining fasting glucose and fasting insulin into a single index. Widely used in research, less so in routine practice, but derivable from two numbers you can request.
Triglyceride-to-HDL ratio. Not a direct insulin measure, but it can be calculated from a standard lipid panel you may already have, and an elevated ratio is associated with insulin resistance. Free, in the sense that the data may already exist in your record.
Why they aren't routine
Partly cost and partly convention — guidelines are built around diagnosing diabetes, and diabetes is defined by glucose. Insulin measurement isn't standardized across laboratories in the way glucose is, which makes reference ranges less consistent.
That's a reasonable clinical position and it also means the earliest phase of the process goes unmeasured for most people.
How to ask
Specifically, and with a reason attached: I'd like to understand my insulin as well as my glucose — would a fasting insulin be reasonable?
If the answer is no, the triglyceride-to-HDL ratio can often be calculated from results you already have, and it costs nothing to ask.
The honest caveat
More testing isn't automatically better. A fasting insulin result without context can generate anxiety without changing what you'd do — which for almost everyone is the same list: protein, carbohydrate quality and timing, movement after meals, resistance training, sleep.
The value is in earlier detection for someone who wants a reason to act, not in the number itself.
Try this week: if you've had a recent lipid panel, look up your triglycerides and HDL. The ratio is one division.
Education, not medical advice. Test selection and interpretation belong with your doctor.