Serum Creatinine, Blood Urea Nitrogen(BUN) and Their Normal Ranges

Creatinine and its normal level

Firstly let's learn what creatinine is. Creatinine is the waste product of muscle metabolism. It's daily production depends on muscle mass. Normally, creatinine produced each day will be excreted through kidneys so as to keep a stable serum creatinine level. Only in renal disorders will creatinine be abnormally elevated. As kidneys have compensated abilities, high creatinine appears when at least 50 percent of kidney function has been damaged.

Normal creatinine levels are between 0.5 to 1.1 mg/dL for an adult female and 0.6 to 1.2 mg/dL for an adult male. Creatinine levels are lower in young children and the elderly as a result of reduced muscle mass.

Creatinine can be measured by mg/dL or umol/L in different countries. 1 mg/dL is equal to 88.4umol/L. Besides, in different countries may have different reference levels.

Blood Urea Nitrogen and its normal level

A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine.

Similar with creatinine, urea nitrogen is mainly filtrated by kidneys and excreted with urine. When kidneys are severely injured, high blood urea nitrogen appears. In other cases, such as heart failure, dehydration, or a diet high in protein can also make your BUN level higher.

Normal levels of BUN are between 10 to 20 mg/dL for an adult and 5 to 18 mg/dL for a child.


Compared with GFR, creatinine and urea nitrogen levels can not immediately reflect kidney functions. Kidney disease has long existed before creatinine and blood urea nitrogen levels rise. For kidney disease sufferers, take treatment earlier can help save and repair more kidney functions.

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