Serum Insulin Concentration (Quantitative)

This test measures the amount of insulin in your blood. Insulin is a hormone made by the pancreas that helps move sugar from your blood into your cells for energy. Your doctor may order it to help diagnose insulin resistance, type 2 diabetes, or low blood sugar (hypoglycemia), or to check how well your diabetes treatment is working.

Your doctor may order this test to check for diabetes, insulin resistance, or other hormonal imbalances. It’s also used to evaluate how well insulin is working in people with known diabetes or suspected hypoglycemia (low blood sugar).

You will usually be asked to fast for about eight hours before the test, because food and drink can raise insulin levels and affect the results. Water is normally allowed. Tell your healthcare provider about all medicines, vitamins, and supplements you use, since some drugs, including insulin and corticosteroids, can change the results.

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a glucose-insulin profile. Bring any medications you’re taking to your appointment.

A healthcare professional will take a small sample of blood from a vein, most often on the inside of your elbow or the back of your hand. The site is cleaned with an antiseptic, an elastic band is wrapped around your upper arm, and a needle is used to collect blood into a tube. You may feel a brief sting, and the whole process usually takes only a few minutes.

A blood sample is taken from a vein, usually in your arm, using a small needle. You may feel a slight pinch, but it usually doesn’t cause discomfort. The sample is sent to a lab for analysis using an immunoassay method to detect insulin levels.

Your results will show how much insulin is in your blood, usually measured in microunits per milliliter (µU/mL), and normal ranges vary slightly between laboratories. Your provider will read your insulin level together with your blood sugar results. High levels can point to insulin resistance or type 2 diabetes, while low levels may suggest reduced insulin production.

Results are reported as mass concentration (typically in picograms per milliliter, pg/mL). Your doctor will compare these results to your clinical picture and other tests to determine if they’re within expected ranges or if further action is needed.