How to Test for Creatinine Levels

Creatinine is a normal waste product of the body produced from muscle breakdown. It is filtered out of the body by the kidney and into the urine. Creatinine levels are determined by blood or urine tests ordered by a physician. Creatinine can be tested as part of a routine physical. It is also more commonly used to monitor the effects of diseases, such as diabetes, or medications that affect kidney function. In acute illnesses, it can also be used to assess the hydration and fluid status of a patient.

Instructions

• 1

  Undergo a simple blood test (ordered by a physician) to determine your creatinine level. Results are run on a chemistry analyzer in a laboratory and are usually available within a day, but can be run urgently within an hour. Creatinine levels can also be measured from a urine sample or on a 24-hour-long collection of urine.

  The blood creatinine level is measured as a concentration of milligrams per deciliter (mg/dl), with normal values of 0.5 to 1.1 in women and 0.6 to 1.2 in men (higher because men have more muscle mass). In the elderly or very thin, creatinine levels may be lower than these reference ranges.

• 2

  Compare the results from both the blood and urine tests to calculate a creatinine clearance rate(CrCl) or a glomerular filtration rate (GFR) to estimate the function of the kidney. The lab will often perform this calculation and include it with the test results. GFR levels are used to stage the severity of chronic kidney disease, from 1 to 5. Stage 5 is advanced end-stage renal failure and an indication for dialysis.

• 3

  Discuss any abnormal results of creatinine levels with your physician. Creatinine levels elevated above normal can indicate conditions such as simple dehydration (too little water in the body), obstruction of kidney function caused by prostate problems or kidney damage from diseases such as diabetes or hypertension. Many drugs, including some common blood pressure medicines and antibiotics, can affect kidney function and require periodic monitoring through creatinine tests. In chronic kidney disease, the creatinine levels will be measured over time and followed serially. Interventions such as dialysis may be necessary in the event actual kidney failure occurs.