What is typically known as diabetes is actually diabetes mellitus. The word diabetes means "running through" & this makes sense because people with diabetes urinate in greater volumes. The word mellitus means sweet since there's a lot of glucose (sugar) in the urine of diabetic.
There is another condition called diabetes insipidus (a vasopressin deficiency - nothing to do with insulin). These patients also pee a lot, but their urine isn't sweet (and yes, back in the day, doctors would taste it to diagnose). So while the word diabetes is used to refer to diabetes mellitus, this can be a bit confusing if you have the other condition.
This Science Byte is focused on diabetes mellitus. I'll bet everyone reading this knows someone who has diabetes - it's fairly common. As you probably know, there are 2 types: type 1 & type 2.
A bit of background first: insulin. It's a hormone that is secreted in response to elevated blood glucose (so after you eat). It works to activate cells to uptake glucose, clearing it from the blood & storing it (or using it - glucose is the cell's main energy source). Diabetics prick their finger to measure their blood glucose - if it's too high or low, they might end up in a coma. Generally though, their glucose levels are higher than normal - which eventually contributes to all the other conditions associated with diabetes (kidney failure, nerve damage, blindness, etc).
Type 1 diabetes: AKA insulin-dependent diabetes, childhood diabetes
People with type 1 diabetes are born with it - they cannot produce insulin (or don't produce nearly enough). Their immune system actually attacks the beta cells in the pancreas that secrete insulin (for unknown reasons). So for them, insulin therapy is necessary (& injected daily - definitely not a cure). This form is less common, comprising about 10% of diabetics in the US.
Type 2 diabetes: AKA insulin-independent diabetes, adult-onset diabetes
Type 2 diabetes typically develops in overweight adults (& with the increasing prevalence of obesity, in teens & children now too). People with type 2 diabetes have normal (or above average) insulin levels in their blood. Instead, they have an insulin insensitivity - the body no long responds to it (or at least not as well as it should). So insulin therapy really doesn't do much for these diabetics. It isn't completely understood what's going on, but obesity causes insulin insensitivity (probably by decreasing the number of insulin-responsive glucose transporters on cells - proteins that take up glucose when stimulated by insulin). Weight loss & exercise are the first line of treatment. Exercise actually increases these glucose transporters in cells. This isn't always enough though & a number of pharmacotherapies are available. All these drugs act to lower blood glucose levels (through different mechanisms I won't get into).
My second cousin (third? The daughter of my mom's cousin..) was born with type 1 diabetes. They've had quite a few scares. My grandpa developed type 2 diabetes - forcing him to eat better & exercise more. If you've somehow been touched by diabetes, I'd love to hear about it in the comments! Questions (or corrections) are welcome too!