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Causes of Type 1 Diabetes

In type 1 diabetes, the immune system mistakenly attacks and destroys the insulin-producing cells (beta cells) that are created by the pancreas. When the insulin-producing cells are destroyed the pancreas is unable to produce any or enough insulin. This leaves the body without the necessary amount of insulin to convert sugar into energy. Then, instead of being transported into the cells where it is needed, sugar builds up in the blood, leading to high blood sugar, or diabetes. The exact cause is unknown.

Causes of Type 2 Diabetes & Prediabetes

In type 2 diabetes and prediabetes (which can lead to Type 2 diabetes), cells in your body become resistant to the action of insulin, which leaves the pancreas unable to make enough insulin to overcome this resistance. Similar to Type 1 diabetes, sugar is unable to get into the cells where it’s needed, and it builds up in the blood, leading to high blood sugar. Diabetes experts do not yet know why this happens, however, there are some risk factors that can make people more prone to diabetes, including, excess body fat, especially around the abdomen.

Causes of Gestational Diabetes

During pregnancy, the placenta produces hormones to sustain a pregnancy. Although the hormones are necessary for any pregnancy, they have effects on other parts of the body. One effect of the hormones is to make women’s cells more resistant to insulin causing gestational diabetes. During the second and third trimesters of pregnancy, the placenta secretes more and more of these hormones, making it even harder for the body to process insulin and convert sugar into energy.

Normally, the pancreas will respond by producing enough extra insulin to overcome this resistance. But sometimes it can't keep up, which results in too little sugar getting into the cells and too much remaining in the blood. This is considered gestational diabetes. This type of diabetes may also be prevented by eating a well-balanced diet during pregnancy. However, no woman should change diet or exercise habits during pregnancy without first discussing options with her healthcare provider.


If you would like to schedule an appointment with an endocrinologist at Northwestern Memorial Hospital, you may call the Physician Referral Service at 1-877-926-4664 or request a first time appointment online.

Last UpdateOctober 20, 2011


To make an appointment with a physician, please call 1-877-926-4664.

New patients can request an appointment online.