Creatinine (Blood Test, Normal and Elevated Levels)

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

An illustration defining creatinine and shows how it is transported through the blood stream to the kidneys and disposed of it in the urine.

What is creatinine?

  • Creatinine is a chemical waste molecule that is generated from muscle metabolism.
  • Creatinine is produced from creatine, a molecule of major importance for energy production in muscles.
  • Approximately 2% of the body's creatine is converted to creatinine every day.
  • Creatinine is transported through the bloodstream to the kidneys. The kidneys filter out most of the creatinine and dispose of it in the urine.
  • Because the muscle mass in the body is relatively constant from day to day, the creatinine production normally remains essentially unchanged on a daily basis.

Why is it important to check blood creatinine levels?

The kidneys maintain the blood creatinine in a normal range. Creatinine has been found to be a fairly reliable indicator of kidney function. Elevated creatinine level signifies impaired kidney function or kidney disease.

As the kidneys become impaired for any reason, the creatinine level in the blood will rise due to poor clearance of creatinine by the kidneys. Abnormally high levels of creatinine thus warn of possible malfunction or failure of the kidneys. It is for this reason that standard blood tests routinely check the amount of creatinine in the blood.

A more precise measure of the kidney function can be estimated by calculating how much creatinine is cleared from the body by the kidneys. This is referred to as creatinine clearance and it estimates the rate of filtration by kidneys (glomerular filtration rate, or GFR). The creatinine clearance can be measured in two ways. It can be calculated (estimated) by a formula using serum (blood) creatinine level, patient's weight, and age. The formula is 140 minus the patient's age in years times their weight in kilograms (times 0.85 for women), divided by 72 times the serum creatinine level in mg/dL. Creatinine clearance can also be more directly measured by collecting a 24-hour urine sample and then drawing a blood sample. The creatinine levels in both urine and blood are determined and compared. Normal creatinine clearance for healthy women is 88-128 mL/min. and 97 to 137 mL/min. in males (normal levels may vary slightly between labs).

Blood urea nitrogen (BUN) level is another indicator of kidney function. Urea is also a metabolic byproduct which can build up if kidney function is impaired. The BUN-to-creatinine ratio generally provides more precise information about kidney function and its possible underlying cause compared with creatinine level alone. BUN also increases with dehydration.

Recently, elevated creatinine levels in infants were associated with bacteremia while elevated levels in adult males have been linked to incresed risk of prostate cancer.

Test tube laying on top of blood lab results.

What are normal blood creatinine levels?

Normal levels of creatinine in the blood are approximately 0.6 to 1.2 milligrams (mg) per deciliter (dL) in adult males and 0.5 to 1.1 milligrams per deciliter in adult females. (In the metric system, a milligram is a unit of weight equal to one-thousandth of a gram, and a deciliter is a unit of volume equal to one-tenth of a liter.)

Muscular young or middle-aged adults may have more creatinine in their blood than the norm for the general population. Elderly persons, on the other hand, may have less creatinine in their blood than the norm. Infants have normal levels of about 0.2 or more, depending on their muscle development. In people with malnutrition, severe weight loss, and long standing illnesses, the muscle mass tends to diminish over time and, therefore, their creatinine level may be lower than expected for their age.

A person with only one kidney may have a normal level of about 1.8 or 1.9. Creatinine levels that reach 2.0 or more in babies and 5.0 or more in adults may indicate severe kidney impairment. The need for a dialysis machine to remove wastes from the blood is based upon several considerations including the BUN, creatinine level, the potassium level and how much fluid the patient is retaining.

A senior man sitting in bed felling fatigued and confused.

Are there any symptoms associated with elevated blood creatinine levels?

The symptoms of kidney dysfunction (renal insufficiency) vary widely. The generally do not correlate with the level of creatinine in the blood.

  • Some people may have an incidental finding of severe kidney disease and elevated creatinine on routine blood work without having any symptoms.
  • In others, depending on the cause of the problem, different symptoms of kidney failure may be present including:
Take the Kidney Disease Quiz
Diabetes and and high blood pressure are the most common causes of longstanding chronic kidney disease.

What are the reasons for elevated blood creatinine?

Any condition that impairs the function of the kidneys is likely to raise the creatinine level in the blood. It is important to recognize whether the process leading to kidney dysfunction (kidney failure, azotemia) is longstanding or recent. Recent elevations may be more easily treated and reversed.

The most common causes of longstanding (chronic) kidney disease in adults are

Other causes of elevated blood creatinine levels are:

  • Certain drugs (for example,cimetidine [Bactrim]) can sometimes cause abnormally elevated creatinine levels.
  • Serum creatinine can also transiently increase after ingestion of a large amount of dietary meat; thus,nutrition can sometimes play a role in creatinine measurement.
  • Kidney infections,rhabdomyolysis (abnormal muscle breakdown) and urinary tract obstruction may also elevate creatinine levels.
Reviewed on 10/12/2016
References
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care

REFERENCES:

MedscapeReference.com. Creatinine Clearance.

Lifeoptions.org. Lab Values Explained.

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