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Creatinine in Blood Tests

When kidney damage is present or suspected, your doctor will ask the laboratory to determine the creatinine level in your blood. Creatinine is a waste substance consisting of tiny molecules that are easily removed from the body by your kidneys, if they are functioning normally. Creatinine is a byproduct of the process of muscle metabolism and is eliminated from the body in the urine. Together with clinical and other laboratory measures, a physician can identify kidney issues and determine the treatment required.

  1. How Creatine Levels are Obtained

    • A sample of your blood is used to determine your creatinine level. Fasting is not required before the specimen is collected. However, it is recommended that patients avoid eating excess protein in the 24 hours before the test, as this can falsely elevate the creatinine level. Strenuous exercise also should be avoided at least 48 hours before the test as this also may generate inaccurate results.

    Normal Creatinine Levels

    • Creatinine is produced at a constant rate by the body. People with a high body mass or muscle density tend to have higher normal levels than those with less body mass. For men, the normal creatinine level is 0.7 to 1.2 mg/dl (milligrams per deciliter). The normal range for women is 0.6 to 1.0 mg/dl. The normal range for children is comparable to that of women.

    High Creatinine Levels

    • A high level of creatinine in the blood may indicate there is a disruption of normal kidney function. Any of the following may be the cause: infection, injury, cancer or dehydration. Elevated creatinine levels also can be the result of conditions that cause deterioration in muscle mass, such as Muscular Dystrophy and rhabdomyolysis.

    Low Creatinine Levels

    • Low creatinine levels in the blood are also possible. Low creatinine levels are found in the elderly, who have reduced muscle mass and lower metabolism. Patients with severe liver disease and pregnant women also may have lower than normal levels. People on very low protein diets also can have a lower than expected level of creatinine in their blood.

    Considerations

    • A physician may order additional tests if your creatinine level is low. These include: a 24-hour urine collection and tests of your urea and nitrogen (BUN) levels. Taken alone, creatinine level is not the most accurate indicator of kidney function. But it is a great screening test.

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