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At a Glance

Why Get Tested?

To help evaluate insulin production, diagnose an insulinoma (insulin-producing tumour), and to help determine the cause of low blood glucose (hypoglycaemia)

When to Get Tested?

If you have hypoglycaemia, if you have symptoms suggesting insulin is being inappropriately produced by your body, and sometimes if you have diabetes and your doctor wants to monitor your insulin production

Sample Required?

A blood sample taken from a vein in your arm

The Test Sample

What is being tested?

Insulin is a hormone that is produced and stored in the beta cells of the pancreas. Insulin is required to regulate blood glucose levels and plays a role in controlling the levels of carbohydrates and fats stored in the body.

When blood glucose levels rise after a meal, insulin allows glucose to be taken up by the body's cells, especially muscle and fat cells, where is it is used for energy production. Insulin then signals to the liver to store the remaining excess blood glucose as carbohydrates and fat, as a form of energy storage.

Humans need insulin on a daily basis to survive. Without insulin, glucose cannot reach most of the body's cells. Without glucose, the cells starve, and blood glucose levels rise to dangerous levels. Eventually, very high glucose levels lead to a life-threatening condition called a diabetic coma.

People with type 1 diabetes produce very little insulin and must take daily insulin injections. People with type 2 diabetes can usually produce insulin but may need oral medications that increase their body's cells response to insulin (the cells may become resistant over time and/or with obesity) or that stimulate he pancreas to produce more insulin. In many cases people with type 2 diabeties may also need to take insulin injections to achieve normal glucose levels.

Insulin and glucose levels must be in balance. An excess amount of insulin in the blood is known as 'hyperinsulinaemia'. This is most often seen with insulinomas (insulin-producing tumours) or with an excess amount of injected insulin, and can be dangerous. It causes hypoglycaemia (low blood glucose levels), which can lead to sweating, rapid heart beat, hunger, confusion, visual problems, and seizures. Since the brain is totally dependent on blood glucose as an energy source, glucose deprivation due to hyperinsulinaemia can lead fairly quickly to death.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.