How does diabetes cause high blood sugar levels?

Type 2 diabetes mellitus causes high blood sugar levels in a number of ways. First, individuals with type 2 diabetes have what is called insulin resistance, meaning that their cells can no longer use insulin to bring sugar out of the blood and into their cells where it can be used. Think of insulin as a key in the door of the cells allowing sugar in; in type 2 diabetes, the lock is broken and the key no longer fits properly. This causes an obvious increase in blood sugars.

Over time, the insulin-producing cells of the pancreas become overworked and burn out. This happens as the body senses high blood sugar (from insulin resistance) and tells the pancreas to make more and more insulin, not understanding that the cells can no longer respond to it. As these pancreatic cells stop working and little to no insulin is made, sugar levels further climb within the blood stream.

Intermountain Registered Dietitians
Nutrition & Dietetics Specialist

If you have type 1 diabetes, your pancreas has stopped—or nearly stopped—making insulin. Insulin allows glucose to cross out of your bloodstream and go into your body's cells—it's like a key that "unlocks" the cells. Without an insulin "key" you have no way to "unlock" your cells to allow glucose from your bloodstream to enter. You also have no way to block the release of glucose from your liver into your bloodstream. Your blood glucose gets too high.

If you have type 2 diabetes, your body's cells have become resistant to insulin. So even though you have an insulin "key," it's as if the cell "lock" is broken so that glucose can't easily get in. Glucose stays in your bloodstream and blood glucose gets too high. Over time, some people with type 2 diabetes also develop trouble making enough insulin (insulin deficiency), which is the same problem that people with type 1 diabetes have.

Geri Spollett

In type 1 diabetes the body cannot produce enough insulin to allow the cells of the body to utilize glucose, which is the simplest form of sugar used for energy. The pancreas is the organ of the body that produces insulin. It is made in beta cells. These tiny cells are scattered throughout the pancreas and they work hard to make the right amount of insulin needed for our body to access to the glucose derived from the foods we eat and to store it for later use in the liver. When the beta cell cannot continue to produce insulin at the amount necessary for using and storing glucose properly, then that glucose remains in the blood stream raising the levels above the normal range. We refer to this as high blood sugar.

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