What is creatinine? What does elevated creatinine mean?

Serum creatinine is one of the most commonly measured products in clinical chemistry laboratories worldwide. 

Creatinine is a chemical waste product in the blood that passes through the kidneys to be filtered and eliminated in urine. It is a by-product of normal muscle function. The more muscle a person has, the more creatinine they produce. Levels of creatinine in the blood reflects both the amount of muscle a person has and their kidney function.

Most men with normal kidney function have approximately 0.6 to 1.2 mg/dL(milligrams/decilitre) of creatinine. Most women with normal kidney function have between 0.5 to 1.1 mg/dL of creatinine. Women usually have lower creatinine levels than men because women on average have less muscle mass than men.

Other factors that may affect the level of creatinine in the blood include body size, activity level and medications.

What does elevated creatinine mean?

When there is kidney damage or kidney disease, and the kidneys are not able to filter waste efficiently there will be a rise of creatinine levels in the blood.

Raised creatinine levels in routine blood tests indicate advanced kidney disease.

Creatinine is produced endogenously within the body and is freely filtered by the glomerulus. These characteristics make creatinine a useful marker for creatinine clearance. If the GFR(glomerular filtration rate, filtration capacity of kidney) is decreased, as is in renal disease, creatinine clearance via the urine is compromised. The reduced GFR will then lead to an increase in plasma(blood) creatinine concentration. 

Plasma creatinine levels may not be affected until significant kidney damage has occurred i.e. a blood creatinine level that is within normal reference range does not indicate a normal functioning kidney.

-Dr Prerna Gaur





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