Ketones, also known as ketone bodies, are chemicals your body produces when it breaks down fat for energy instead of glucose (sugar). This typically happens when glucose is in short supply, such as during fasting, prolonged exercise, low-carbohydrate diets, or when insulin is insufficient to allow glucose into cells (as in diabetes)

. There are three main types of ketone bodies produced by the liver: acetone, acetoacetate, and beta-hydroxybutyrate (BHB). These ketones serve as an alternative fuel source for the body and brain when glucose is not readily available. BHB is the ketone body most efficiently used for energy

. In normal amounts, ketones are a safe and natural backup energy source. However, high levels of ketones, especially in people with type 1 diabetes, can lead to a dangerous condition called diabetic ketoacidosis (DKA), which requires urgent medical attention

. From a chemical perspective, ketones are organic compounds characterized by a carbonyl group (C=O) bonded to two carbon atoms. Many biological molecules, such as certain sugars (ketoses) and steroids, contain ketone groups

. In summary:

• Ketones are acids (ketone bodies) produced when the body burns fat for energy instead of glucose.
• They provide an alternative energy source during glucose scarcity.
• Produced mainly by the liver from fat breakdown.
• Normal in small amounts; high levels can be dangerous, especially in diabetes.
• Chemically, ketones have a carbonyl group bonded to two carbon atoms.

This dual nature of ketones-both as biological energy molecules and as organic chemical compounds-makes them important in metabolism, nutrition, and medicine