Why are there ketones in my urine?

When ketones show up in your urine, it's a sign that your diabetes may be getting out of control. Ketones are acids that your body produces when it is not getting enough fuel to function properly. Your body gets fuel by a process that starts with turning the food you eat into sugar (glucose) in your bloodstream. Your pancreas then produces a hormone called insulin, which helps move the glucose from your blood into your cells to be used for fuel. With diabetes, your body either doesn't produce enough insulin or doesn't respond normally to the insulin you do have, so it can't use glucose efficiently. The glucose is just flushed out of your body in your urine. Since you can't use glucose for fuel, it starts using fat instead -- and the fat-burning process produces the acids known as ketones.

Ketones in the urine show that fat is being burned for fuel by your body. This typically occurs when you do not have enough insulin in your body to metabolize sugar as fuel or when you are fasting. Thus, spilling ketones into your urine means either that your body is dangerously low on insulin or that your diet is working. When ketones build up due to a lack of insulin, the condition is called "ketoacidosis," and it can be dangerous.

Ketoacidosis is more common in type 1 diabetes, occurring when people are first diagnosed with diabetes, when they stop taking insulin for some reason, or when they are ill. Most people with ketoacidosis develop symptoms that make them consult a doctor, such as stomach pain, nausea or vomiting, rapid breathing, frequent urination, extreme thirst, or fatigue.

If you are on a diet that does not provide enough calories to your body, then your body burns fat for energy. This is the effect you want from your diet, because burning fat will cause you to lose weight. A by-product of fat metabolism, however, is ketones, and these ketones spill into your urine just as they do in ketoacidosis. If you are feeling fine and controlling your blood glucose, then the ketones in your urine are probably a safe result of your diet.