Ketone bodies are usually absent in urine, but low levels may be detected during conditions of physiological stress such as fasting, rapid weight loss, frequent strenuous exercise or prolonged vomiting. The presence of ketones in these situations is due to either inadequate intake or increased loss of carbohydrates.

High levels of ketones are present in the urine of individuals with uncontrolled diabetes. In diabetes the ketones are present because the body's ability to metabolize carbohydrates is defective.