The plus sign of ketone bodies is a qualitative test that generally refers to the plus sign of ketone bodies in the urine, with a maximum of 4 plus signs usually being a strong positive. Ketone bodies are intermediate metabolites in the oxidative metabolism of fats and include acetoacetic acid, beta-hydroxybutyric acid, and acetone. In healthy individuals, small amounts of ketone bodies are present in the blood at a ratio of 78% beta-hydroxybutyric acid, 20% acetoacetic acid, and 2% acetone. When the rate of production of ketone bodies in the liver exceeds the rate of utilization by extrahepatic tissues, the ketone bodies in the blood increase, ketonemia can occur, and excessive ketone bodies are excreted in the urine called ketonuria. Urine ketone body test is mainly used for glucose metabolism disorder and fat incomplete oxidation judgment and evaluation. Ketone bodies must be timely to the hospital, under the guidance of the doctor’s treatment.