Ketones: Definition and Overview

What are ketones?

Ketones are by-products formed when the body breaks down fat for energy. When the body is starved of glucose or, as in the case of Type 1 diabetes, does not have enough insulin to use the glucose that is in the bloodstream, it begins breaking down fat reserves for energy. Unlike glucose, which “burns clean,” the breakdown of fat creates potentially toxic by-products called ketones, which accumulate in the blood. An excessive amount of ketones in the blood is called ketosis. When the kidneys filter ketones into the urine, the condition is called ketonuria and can be detected by urine ketone tests.

What do ketones do?

If enough ketones accumulate in the blood, they can cause a potentially life-threatening chemical imbalance known as ketoacidosis. The symptoms of ketoacidosis include nausea, vomiting, tiredness, frequent urination, and a fruity odor to the breath. Anyone with symptoms of ketoacidosis should seek medical help immediately.

What is ketoacidosis?

Ketoacidosis is often what causes people to first be diagnosed with Type 1 diabetes: Beta cells in the pancreas stop making enough insulin, thus preventing body cells from getting energy in the form of glucose. The body responds by burning fats for fuel, creating an excess of ketones in the blood. As dehydration also sets in, the person develops ketoacidosis. The nausea and vomiting that accompany ketoacidosis are sometimes mistaken for the symptoms of a bad flu.

People with diabetes, particularly those with Type 1 diabetes, are at increased risk of ketoacidosis when they are sick. The stress of illness tends to raise blood glucose levels. But since illness often decreases a person’s appetite, resulting in less food intake than usual, some people mistakenly decrease their insulin dosages. In fact, increased amounts of insulin are often needed when a person is sick. It is also important to continue consuming some form of carbohydrate, drinking fluids, and monitoring blood sugar levels.

Exercise can also contribute to ketoacidosis. If a person does not have sufficient insulin when he or she starts exercising, the increased energy demands of exercise force the body to begin burning fat for fuel, producing ketones.

How to treat ketoacidosis?

What can you do to prevent ketoacidosis? Set up a sick-day plan with your health-care providers in advance. Always check your urine when you’re sick, and if there are ketones, contact your health-care team for advice. If you plan to exercise and your blood sugar is high (for example, above 240 mg/dl), be sure to check your urine for ketones. If there are ketones, find the underlying problem before exercising, because exercise will only make the problem worse. Fortunately, ketoacidosis, while life-threatening, takes hours or days to develop, giving you ample time to detect it and seek appropriate treatment.

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