Insulin - Fasting Test

Insulin is a hormone that is produced and stored in the beta cells of the pancreas. It is vital for the transportation and storage of glucose, the body's main source of energy. Insulin helps transport glucose from the blood to within cells, helps regulate blood glucose levels, and has a role in lipid metabolism. This test measures the amount of insulin in the blood.

Insulin and glucose blood levels must be in balance. After a meal, carbohydrates usually are broken down into glucose and other simple sugars. This causes the blood glucose level to rise and stimulates the pancreas to release insulin into the blood. As glucose moves into cells, the level in the blood decreases and release of insulin by the pancreas decreases.

If an individual is not able to produce enough insulin, or if the body's cells are resistant to its effects (insulin resistance), glucose cannot reach most of the body's cells and the cells starve, while blood glucose rises to an unhealthy level. This can cause disturbances in normal metabolic processes that result in various disorders and complications, including kidney disease, cardiovascular disease, and vision and neurological problems.

Diabetes, a disorder associated with high glucose levels and decreased insulin effects, can be a life-threatening condition. People with type 1 diabetes produce very little insulin and so eventually require insulin supplementation therapy. Type 2 diabetes is generally related to insulin resistance, which increases with time.

With insulin resistance, the body is unable to respond to the effects of insulin. The body compensates by producing additional amounts of the hormone. This results in a high level of insulin in the blood (hyperinsulinemia) and over-stimulation of some tissues that have remained insulin-sensitive. Over time, this process causes an imbalance in the relationship between glucose and insulin and, without treatment, may eventually cause health complications affecting various parts of the body.