The two main types
Type 1 diabetes means that the pancreas has stopped making insulin. You have to replace this with injected insulin. This is vital to keep you alive and you have to take it every day.
Someone with Type 2 diabetes still makes insulin, but it either is not enough or can't get to the cells to do its work. This type of diabetes is often treated with tablets.
If you have Type 1 diabetes, you tend to feel very poorly quite quickly until you are treated.
But Type 2 diabetes develops much more gradually so it may not come out of the blue.