A creatinine blood test is a medical test used to measure the level of creatinine in the blood. Creatinine is a waste product produced by muscles and released into the blood. The kidneys filter creatinine out of the blood and excrete it in the urine.

The creatinine blood test is primarily used to assess kidney function. If the kidneys are not functioning properly, creatinine may accumulate in the blood, leading to high creatinine levels. This can be an indication of kidney disease or other conditions that affect the kidneys.

The test is usually performed by taking a small sample of blood from a vein in the arm. The sample is then sent to a laboratory for analysis. Results are usually available within a few days.

Normal levels of creatinine in the blood vary depending on age, gender, and muscle mass. In general, normal levels range from 0.6 to 1.2 milligrams per deciliter (mg/dL) in adult males and 0.5 to 1.1 mg/dL in adult females. High levels of creatinine may indicate kidney disease or other conditions, while low levels may indicate a lack of muscle mass or malnutrition.