Does Taking Creatine Supplements Affect Creatinine Levels in Urine?

Creatinine tests are commonly used by your doctor as a quick and easy way to check your kidney function. Creatine supplements are used by athletes and fitness enthusiasts to assist in muscle growth and increase short-term endurance. Creatine is naturally produced by your body and broken down into creatinine. Supplements containing high levels of creatine can artificially elevate levels of creatinine in your blood and urine.

Creatine is a natural product of amino acid in your body. In your muscles, creatine is charged with energy by chemically linking it to a phosphate group, making phosphocreatine. During intense, short-duration exercise — such as weightlifting or sprinting — phosphocreatine is used to rapidly regenerate muscle energy, but is exhausted within approximately 10 seconds. It is not clear that creatine supplements can increase muscle creatine levels in healthy people, according to the University of Maryland Medical Center.

Creatinine itself is not toxic to your body; A high level of creatinine indicated your kidneys are not filtering waste, some of which may be toxic. Creatinine is produced by the breakdown of creatine or phosphocreatine by your muscles. Under normal conditions, your body produces creatinine at a constant rate. Creatinine is filtered out of your blood by your kidneys, and removed via urine.

Your doctor will measure creatinine levels in your blood, along with many other tests, when monitoring your kidney function. Measuring creatinine levels in the blood allows your doctor to easily check whether your kidneys are effectively filtering out waste. If creatinine levels are high, your kidneys may be impaired and filtering waste slowly, allowing waste products such as creatinine to build up in your body. Creatinine levels in your urine will be lower than normal if you have impaired kidney function.

If you are taking a creatine supplement, tell your doctor, as it can bias the results of a creatinine test. You should not take a creatine supplement if you are currently under a doctor's care, especially for kidney disease. Creatine can cause an increase in urination or water retention, even in healthy individuals, placing additional stress on the kidneys.