Insulin, a potent hormone released by the pancreas, keeps blood sugar levels in a healthy range. People with type 1 diabetes do not make enough insulin to maintain normal blood sugar levels. In type 2 diabetes, however, insulin levels can actually spike in an effort to overcome the body's resistance to its effects. Other causes of high insulin levels include pregnancy and insulin-secreting tumors.
The development of type 2 diabetes is preceded by a condition known as insulin resistance, or impaired glucose tolerance. Risk factors for insulin resistance include being overweight or obese, lack of regular physical activity and older age. Insulin resistance occurs when the body's tissues are no longer sensitive to the effects of insulin, causing blood sugar levels to rise above normal. As blood sugar levels increase, insulin levels surge as well. In the early stages of type 2 diabetes, insulin levels typically remain higher than normal. With long-standing type 2 diabetes, however, the insulin-producing cells of the pancreas may burn out, causing reduced insulin levels. When this occurs, insulin injections may become necessary to control blood sugar.
Over the course of a normal pregnancy, insulin levels rise as the fetus grows larger. By late pregnancy, sensitivity to insulin decreases, causing insulin levels to spike. Although insulin resistance is normal in late-stage pregnancy, some develop a pregnancy-related form of diabetes known as gestational diabetes. Women with this condition typically have further increases in their insulin levels. Although estimates vary, the American Diabetes Association reports that as many as 18 percent of pregnancies are complicated by gestational diabetes. Being overweight before pregnancy, a family history of diabetes and a personal history of high blood pressure are risk factors for gestational diabetes.
In rare cases, an insulin-secreting tumor, called an insulinoma, can cause high insulin levels. Insulinomas are typically small tumors that are usually found in the pancreas. Women over the age of 50 are most commonly affected. The majority of insulinomas are not cancerous, report authors of a November 2008 review article in "Cases Journal." Even so, an insulinoma can cause dangerously low blood sugar levels due to surges in insulin produced by the tumor. Symptoms of low blood sugar include tremors, sweating, dizziness and confusion.
Depending on the underlying condition, high insulin levels can have different effects. In people with insulin resistance, spikes in insulin can signal the development of type 2 diabetes. While insulin levels are generally not measured directly, the American Diabetes Association recommends close monitoring of blood sugar levels in people with insulin resistance to help prevent the development of type 2 diabetes. The American College of Obstetricians and Gynecologists recommends that all pregnant women be screened for gestational diabetes during their third trimester. When an insulin-secreting tumor is suspected, a special CT scan, MRI or ultrasound is usually performed to pinpoint the exact location before surgery to remove the tumor.