Insulin (Postprandial)

What is postprandial insulin?

After a meal, the digested carbohydrates raise blood sugar, and in response the pancreas releases insulin into the blood. In a healthy metabolism, insulin rises quickly, allows sugar to enter the cells and falls again as blood sugar stabilizes. The postprandial insulin test measures the amount of insulin in the blood at a set time after a meal, usually at the second hour.

Because this test shows how the pancreas works under load, it can reveal some forms of insulin resistance that fasting insulin alone cannot detect. The laboratory does not report a fixed reference range for postprandial insulin; the result is interpreted by comparing it with postprandial blood sugar measured at the same time and with fasting values. The measurement is performed on serum using an immunological method and reported in µIU/mL. Your doctor may also order a similar assessment with several measurements during a glucose load test using a sugary solution.

When is the postprandial insulin test ordered?

Postprandial insulin is usually ordered together with fasting insulin and blood sugar to get a complete picture of how the metabolism responds to a meal. It is particularly helpful for people who experience trembling, sweating and sudden hunger a few hours after eating, to understand how these complaints relate to the insulin response.

• Trembling, sweating, palpitations and sudden hunger a few hours after eating
• Suspected insulin resistance despite normal fasting values
• Polycystic ovary syndrome and difficulty losing weight
• A history of prediabetes or gestational diabetes
• Monitoring the insulin response after lifestyle changes or treatment

How do you prepare for the postprandial insulin test?

The test is usually scheduled for the same morning as the fasting sample: first, fasting blood is drawn after an overnight fast, then a regular breakfast containing carbohydrates is eaten as recommended by your doctor. The postprandial sample is usually taken 2 hours after you start eating; during this time nothing else should be eaten and nothing but water should be drunk. Because the duration and content of the meal can affect the result, it is important to follow the instructions you are given.

Avoiding strenuous physical activity and smoking during the waiting period makes the result more reliable. Cortisone, diabetes medications and insulin injections can affect the result; decide with your doctor at what time to take your medications. If you take high-dose biotin supplements, mention this as well. Blood is drawn from a vein in the arm; a Curavita nurse can take the postprandial sample at the specified time at your home or workplace.

What does the postprandial insulin result mean?

A postprandial insulin level that is much higher than expected, or that is still markedly high at the second hour, suggests that the body needs extra insulin to regulate blood sugar, in other words insulin resistance. This is common with excess weight, PCOS and prediabetes. In some people, an excessive and delayed insulin response can cause blood sugar to drop too low hours after a meal (reactive hypoglycemia).

If insulin does not rise sufficiently despite a meal, this may indicate that the pancreas's capacity to produce insulin has decreased; if blood sugar is also high, an evaluation for diabetes is needed. Because no fixed reference range is reported for this test, the result on its own is not classified as normal or abnormal. Laboratories' approaches may differ, and age, sex and the content of the meal also affect interpretation; the laboratory's information on this point is shown separately on this page. Your doctor will establish what your result means, together with your fasting values, blood sugar and symptoms.