Type 2 diabetes develops when the body becomes resistant to
insulin or when the pancreas stops producing enough insulin.
Exactly why this happens is unknown, although excess weight
and inactivity seem to be important factors.

Insulin is a hormone that comes from the pancreas, a gland
located just behind the stomach. When you eat, the pancreas
secretes insulin into the bloodstream. As insulin circulates,
it acts like a key by unlocking microscopic doors that allow
sugar to enter your cells. Insulin lowers the amount of sugar
in your bloodstream. As your blood sugar level drops, so does
the secretion of insulin from your pancreas.

Glucose — sugar — is a main source of energy for the cells that
make up muscles and other tissues. Glucose comes from two
major sources: the food you eat and your liver. After intestinal
digestion and absorption, sugar is absorbed into the bloodstream.
Normally, sugar then enters cells with the help of insulin.

The liver acts as a glucose storage and manufacturing center.
When your insulin levels are low — when you haven’t eaten in
a while, for example — the liver metabolizes stored glycogen
into glucose to keep your glucose level within a normal range.

In type 2 diabetes, this process works improperly. Instead of
moving into your cells, sugar builds up in your bloodstream.
This occurs when your pancreas doesn’t make enough insulin
or your cells become resistant to the action of insulin.

In type 1 diabetes, which is much less common, the pancreas
produces little or no insulin.

Next post: Risk Factors.