What it measures
The fasting insulin resistance index is worked out from fasting insulin and fasting glucose taken in the same sample. It gives one figure for how much insulin the body needs to keep glucose steady while fasting.
Why people test it
- Used as a simple estimate of insulin resistance, where the body needs more insulin to control glucose.
- Checked by people with polycystic ovary syndrome or a family history of type 2 diabetes.
- Insulin can rise while glucose still looks normal, so the index adds to glucose and HbA1c results.
Typical range
There is no single agreed cut-off. Ranges vary by lab, method, age and sex, and your report shows the lab's own range where it gives one.
Finger-prick or vein?
Taken from a vein, and providers offer it only as a vein draw. Haemolysis lowers insulin results, and finger-prick samples haemolyse more easily.
It needs a fasting sample, as both insulin and glucose rise after eating.