Creatinine and Creatinine Clearance

Blood Creatinine

Results

Creatinine and creatinine clearance tests measure creatinine levels in your blood and urine to give information about how well your kidneys are working. The creatinine clearance value is found from the amounts of creatinine in the urine and blood and from the amount of urine you pass in 24 hours. This value is the amount of blood cleared of creatinine per minute, based on your body size.

Normal

Normal results may vary from lab to lab.

Blood creatinine and creatinine clearance

Blood creatinine:	Men 0.6–1.2 milligrams per deciliter (mg/dL) or 53-106 micromoles/L (mcmol/L) Women 0.5–1.1 mg/dL or 44–97 mcmol/L Teen 0.5–1.0 mg/dL Child 0.3–0.7 mg/dL Newborn 0.3–1.2mg/dL
Creatinine clearance:	Men 90–140 milliliters per minute (mL/min) or 1.78–2.32 milliters per second (mL/sec) Women 87–107 mL/min or 1.45-1.78 mL/sec

Creatinine clearance values normally go up as you get older (normal values go down by 6.5 mL/min for every 10 years past the age of 20).

 

BUN-to-creatinine ratio

Over 12 months of age:	10:1–20:1
Infants less than 12 months of age:	Up to 30:1

 

High values

• High creatinine blood levels. High creatinine blood levels can mean serious kidney damage or disease is present. Kidney damage can be caused by a life-threatening infection, shock, cancer, or low blood flow to the kidneys. Other conditions that can cause high blood creatinine levels include blockage of the urinary tract (such as by a kidney stone), heart failure, dehydration, excessive blood loss that causes shock, gout, or muscle conditions (such as rhabdomyolysis, gigantism, acromegaly, myasthenia gravis, muscular dystrophy, and polymyositis). Usually a high blood creatinine level means that the creatinine clearance value is lower than normal.
• High creatinine clearance. High creatinine clearance values can be caused by strenuous exercise, muscle injury (especially crushing injuries), burns, carbon monoxide poisoning, hypothyroidism, and pregnancy.
• High BUN-to-creatinine ratio. High BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by shock or severe dehydration. A blockage in the urinary tract (such as a kidney stone) can cause a high BUN-to-creatinine ratio. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.

Low values

• Low blood creatinine levels. Low blood creatinine levels can mean lower muscle mass caused by a disease, such as muscular dystrophy, or by aging. Low levels can also mean some types of severe liver disease or a diet very low in protein. Pregnancy can also cause low blood creatinine levels.
• Low creatinine clearance. Low creatinine clearance levels can mean serious kidney damage is present. Kidney damage can be from conditions such as a life-threatening infection, shock, cancer, low blood flow to the kidneys, or urinary tract blockage. Other conditions, such as heart failure, dehydration, and liver disease (cirrhosis), can also cause low creatinine clearance levels.
• Low BUN-to-creatinine ratio A low BUN-to-creatinine ratio may be associated with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, and the use of certain medications.

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Author:	Jan Nissl, RN, BS	Last Updated: August 21, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine
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