A test done on a sample of blood to measure the amount of certain substances in the body. These substances include electrolytes (such as sodium, potassium, and chloride), fats, proteins, glucose (sugar), and enzymes. Blood chemistry tests give important information about how well a person’s kidneys, liver, and other organs are working. An abnormal amount of a substance in the blood can be a sign of disease or side effect of treatment. Blood chemistry tests are used to help diagnose and monitor many conditions before, during, and after treatment. Also called blood chemistry study.