There is no one test that can directly detect insulin resistance. Instead, a doctor will look at a patient's entire clinical picture and may suspect that the patient has insulin resistance if he has increased glucose levels, increased levels of triglycerides and LDL, and decreased concentrations of HDL. Laboratory tests most likely to be ordered include:
- Glucose. This is usually performed fasting but, in some cases, a doctor may also order a GTT (glucose tolerance test - several glucose tests that are taken before and at timed intervals after a glucose challenge). The goal of glucose testing is to determine whether a patient has an impaired response to glucose.
- Lipid profile. This measures the HDL, LDL, triglycerides, and total cholesterol. If the triglycerides are significantly elevated, a DLDL (direct measurement of the LDL) may need to be done.
- One of the most common ways of detecting insulin resistance is by using the homeostatic model assessment (HOMA). It involves measuring glucose and insulin levels and then using a calculation to estimate beta cell function and insulin sensitivity.
Other laboratory tests that may be ordered to help evaluate insulin resistance and provide additional information include:
- Insulin. The fasting insulin test is variable, but insulin levels will usually be elevated in those with significant insulin resistance.
- hs-CRP. This is a measure of low levels of inflammation that may be done as part of an evaluation of cardiac risk. It may be increased with insulin resistance.
- sdLDL. This is a measurement of the number of small dense low-density lipoprotein molecules a patient has. This test is not ordered frequently but may be measured as part of a lipoprotein subfractions test.
- Insulin tolerance test (ITT). Not widely used but is one method for determining insulin sensitivity (or resistance), especially in obese individuals and those with PCOS. This test involves an IV-infusion of insulin, with subsequent measurements of glucose and insulin levels.
Specific insulin suppression tests may also be ordered in a research setting to study insulin resistance but are not generally used in a clinical setting.