Insulin is a hormone made by your pancreas. It allows your cells to use glucose (sugar) for energy.
Insulin resistance is the name given to when cells of the body don’t respond properly to the hormone insulin. Insulin resistance is the driving factor that leads to type 2 diabetes, gestational diabetes and prediabetes.
The body produces insulin when glucose starts to be released into the bloodstream from the digestion of carbohydrates in the diet. Normally this insulin response triggers glucose being taken into body cells, to be used for energy, and inhibits the body from using fat for energy. The concentration of glucose in the blood decreases as a result, staying within the normal range even when a large amount of carbohydrates is consumed. When the body produces insulin under conditions of insulin resistance, the cells are resistant to the insulin and are unable to use it as effectively, leading to high blood sugar. Beta cells in the pancreas subsequently increase their production of insulin, further contributing to a high blood insulin level. This often remains undetected and can contribute to the development of type 2 diabetes or latent autoimmune diabetes of adults. Although this type of chronic insulin resistance is harmful, during acute illness it is actually a well-evolved protective mechanism. Recent investigations have revealed that insulin resistance helps to conserve the brain's glucose supply by preventing muscles from taking up excessive glucose. In theory, insulin resistance should even be strengthened under harsh metabolic conditions such as pregnancy, during which the expanding fetal brain demands more glucose.
People who develop type 2 diabetes usually pass through earlier stages of insulin resistance and prediabetes, although those often go undiagnosed. Insulin resistance is a syndrome (a set of signs and symptoms) resulting from reduced insulin activity; it is also part of a larger constellation of symptoms called the metabolic syndrome.
Insulin resistance may also develop in patients who have recently experienced abdominal or bariatric procedures. This acute form of insulin resistance that may result post-operatively tends to increase over the short term, with sensitivity to insulin typically returning to patients after about five days.