Ketosis (metabolic state of elevated ketone bodies)

Key components and how they form

When carbohydrate intake is low or glycogen stores fall, the body increases fat breakdown and hepatic conversion of fatty acids into ketone bodies. The main ketones are listed below:

• Acetoacetate — one of the first ketones produced during ketogenesis.
• Beta‑hydroxybutyrate — often present at the highest concentration in blood and used by many tissues for energy.
• Acetone — a volatile byproduct that can be detected on the breath.

These compounds can be measured directly or inferred: for example, blood tests detect beta‑hydroxybutyrate, urine strips detect acetoacetate, and breath devices can register acetone. See more on testing methods via ketone bodies, blood and urine.

Common causes and situations

• Fasting or prolonged calorie restriction, which depletes glycogen and shifts metabolism.
• Very low‑carbohydrate or ketogenic diets that intentionally limit glucose availability.
• Extended, intense exercise that uses up carbohydrate stores.
• Some medical conditions that alter insulin or carbohydrate metabolism; the liver (liver) plays a central role in generating ketones.

Ketosis is distinct from diabetic ketoacidosis (DKA): nutritional or physiological ketosis is a controlled, adaptive state, whereas DKA is a dangerous acutely acidotic condition requiring urgent care. Elevated acetone is a typical sign and can be referenced as acetone in breath tests.

Clinically and culturally, ketosis has been used therapeutically (for example, in refractory epilepsy and under study for weight loss and some neurological diseases) but also carries short‑term side effects such as fatigue, headache or electrolyte changes. Anyone considering a ketogenic approach for health reasons should consult healthcare professionals to weigh benefits, monitor safety and distinguish safe ketosis from pathological states.