To have energy you need sugar, so there's a little bit of sugar in your blood at all times. Your body uses a chemical called "insulin" to let this sugar into your cells. Insulin is produced in the pancreas, which is an organ that sits behind your stomach.
Most cells in your body have insulin receptors on their outer surface. Insulin fits into these receptors like a key opening a lock. When this connection is made, it signals special transporter proteins to move up to the cell membrane, where they allow more sugar molecules to enter the cell. This sugar fuels your body's cells, giving them the energy they need to work properly and repair themselves.
Normally, your body is able to maintain proper levels of sugar in your blood and inside your cells. But in people with diabetes, the body's cells stay locked and sugar can't get in to provide energy. This causes too much sugar to build up in the blood. Over time, high levels of sugar in the blood can lead to serious health problems in the eyes, feet and hands, kidneys, and heart.
There are two main types of diabetes -- type 1 and type 2.
Type 1 diabetes usually begins in young children and teenagers. People with this type of diabetes have a pancreas that doesn't produce enough insulin -- or stops producing it altogether. This means they need to have insulin shots on a regular basis to help keep their blood sugar at the right level.
Type 2 diabetes happens in people whose pancreas DOES make insulin. But in a person with this type of diabetes, the insulin receptors on the cells' surface become less sensitive. Since the receptors don't respond to the insulin anymore, sugar stays locked out of the cells and remains in the blood. Type 2 diabetes is usually seen in older people. Also, things like being overweight and smoking can make a person more likely to get type 2 diabetes. This is especially true for those who are African American or Hispanic.