Ketoacidosis is a metabolic imbalance caused by an excess of ketone bodies, a breakdown product of fatty acids and amino acids. These increase the acidity of blood. It's common with type I diabetes and alcoholism. The condition can quickly lead to coma and, eventually, death. It's a medical emergency and requires immediate medical treatment even if appropriate aid is provided by first responders.
Although the ketones can be detected in the blood and urine, they also create acetone which can be smelled on the breath.
Ketoacidosis develops in diabetics from a combination of low insulin, high blood sugar and dehydration.
In alcoholism, alcohol creates dehydration and eliminates a precursor to the metabolism of other sugars into glucose.