Ketoacidosis is a type of metabolic acidosis which is caused by high concentrations of ketone bodies, formed by the deamination of amino acids, and the breakdown of fatty acids. This is most common in untreated type 1 diabetes mellitus, when the liver breaks down fat and proteins in response to a perceived need for respiratory substrate. It can also occur with people undergoing hunger strikes, fasting over 3 days, or people starving to death as the body is forced to break down fat for sustenance due to their lack of outside nutrition.

Ketoacidosis can be smelled on a person's breath. It is often described as smelling like fruit or paint thinner.http://www.nlm.nih.gov/medlineplus/ency/article/000320.htm

Ketoacidosis should not be confused with ketosis, which is one of the body's normal processes for the metabolism of body fat. In ketoacidosis, the accumulation of keto acids is so severe that the pH of the blood is substantially decreased.