How do you measure insulin resistance?

The gold standard is the so-called insulin clamp: you receive insulin through a drip while blood sugar is kept artificially stable. The more glucose is needed to maintain that balance, the more sensitive your body is to insulin. This method is very accurate but also time-consuming and expensive, so it is rarely available outside research centres.

For everyday clinical use, HOMA is by far the most widely used method. It is calculated from two fasting blood values: blood sugar and insulin. That makes it simple and inexpensive, but the cut-off values for 'too high' differ by age, sex and ethnic background. The same applies to QUICKI, a comparable formula that is also based on fasting blood values.

If you also want to see how the body responds after eating sugar, the Matsuda Index and ISSI-2 are useful additions. These are calculated from multiple blood draws taken after drinking a sugar solution. That provides more information than fasting values alone, but also takes more time.

There are also methods that map adipose tissue specifically. The Adipo-IR index estimates how well insulin suppresses the breakdown of fat: you multiply fasting insulin by fasting free fatty acids. Its agreement with the gold standard is moderate. In men, an abdominal fat thickness (in front of the peritoneum) of 1.2 cm or more measured by ultrasound proved a useful cut-off; in women, the thickness of subcutaneous abdominal fat worked better, with a cut-off of 1.1 cm. These ultrasound-based cut-offs have so far only been studied in an Asian population and are therefore not broadly applicable.

The Atherogenic Index of Plasma, a blood lipid calculation normally used for cardiovascular risk, was associated with insulin resistance in one observational study. That is insufficient to rely on it diagnostically at this point.