What is measured
- Fasting insulin: how much insulin the body needs to hold blood sugar steady while fasting
- Fasting glucose: the blood sugar level at the same moment
- HOMA-IR: an index calculated from those two numbers
HOMA-IR is worked out by multiplying fasting glucose in mmol/L by fasting insulin in mIU/L, then dividing by 22.5. It is an estimate rather than a direct measurement, but it gives one number you can track over time.
How the test is done
Blood is drawn after an 8 to 12 hour fast. Plain water is allowed throughout.
Insulin and glucose must come from the same draw, because HOMA-IR only means anything when both numbers are from the same moment. Insulin samples also need correct handling at the laboratory, so this test goes to a partner lab that runs it routinely.
Hard training, acute illness and a short night of sleep before the test can all shift the reading. If any of those applies, it is better to postpone.
How results are read
Two people can share the same fasting glucose and have very different fasting insulin, and that is exactly the information lost when only blood sugar is measured.
Take two people at 5.2 mmol/L fasting glucose. On paper they look alike. If one needs far more insulin to hold that reading, their body is working harder for the same result.
There is no single universally accepted HOMA-IR threshold. Values differ with the insulin assay a laboratory uses and with the population studied, and research in Asian populations often applies lower values than international ranges. That makes the number more useful as a personal baseline you retest against than as a pass or fail.
