What is insulin?

Insulin is a hormone made in your pancreas, which lies just behind your stomach. It helps our bodies use glucose for energy. Everyone with Type 1 diabetes and some people with Type 2 diabetes need to take insulin - either by injection or a pump - to control their blood glucose levels (also called blood sugar levels). 

Insulin works as a chemical messenger that helps your body use the glucose in your blood to give you energy. You can think of it as the key that unlocks the door to the body's cells. Once the door is unlocked, glucose can enter the cells where it is used as fuel.

In Type 1 diabetes the body is unable to produce any insulin so there is no key to unlock the door, and the glucose builds up in the blood.

• The body can't use glucose to provide energy, so tries to get it from elsewhere and starts to break down stores of fat and protein instead. Because the body doesn't use the glucose it ends up passing into the urine.
• Nobody knows for sure why these insulin-producing cells have been destroyed, but the most likely cause is the body having an abnormal reaction to the cells. This may be triggered by a virus or other infection.

You can find out more here. 

In Type 2 diabetes there is not enough insulin (or the insulin isn't working properly), so the cells are only partially unlocked and glucose builds up in the blood.