Health Encyclopedia

Creatinine - serum

Definition

Creatinine is a breakdown product of creatine, which is an important part of muscle. A serum creatinine test measures the amount of creatinine in the blood.

Creatinine can also be measured with a urine test.

Alternative Names

Serum creatinine

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

The health care provider may tell you to stop taking certain drugs that may affect the test. Such drugs include:

Aminoglycosides (for example, gentamicin)
Bactrim
Cimetidine
Heavy metal chemotherapy drugs (for example, Cisplatin)
Nephrotoxic drugs such as cephalosporins (for example, cefoxitin)

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

The test is done to evaluate kidney function. If kidney function is abnormal, creatinine levels will increase in the blood, due to decreased excretion of creatinine in the urine. Creatinine levels also vary according to a person's size and muscle mass.

Normal Values

A normal value is 0.8 to 1.4 mg/dL.

Females usually have a lower creatinine than males, because they usually have less muscle mass.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher than normal levels may indicate:

Acute tubular necrosis
Dehydration
Diabetic nephropathy
Eclampsia (a condition of pregnancy that includes seizures)
Glomerulonephritis
Kidney failure
Muscular dystrophy
Preeclampsia (pregnancy-induced hypertension)
Pyelonephritis
Reduced kidney blood flow (shock, congestive heart failure)
Rhabdomyolysis
Urinary tract obstruction

Lower than normal levels may indicate:

Muscular dystrophy (late stage)
Myasthenia gravis

Additional conditions under which the test may be performed:

Acute nephritic syndrome
Alport syndrome
Atheroembolic kidney disease
Chronic kidney failure
Cushing syndrome
Dementia due to metabolic causes
Dermatomyositis
Digitalis toxicity
Ectopic Cushing syndrome
End-stage renal disease
Epilepsy
Generalized tonic-clonic seizure
Goodpasture syndrome
Hemolytic-uremic syndrome (HUS)
Hepatorenal syndrome
Interstitial nephritis
Lupus nephritis
Malignant hypertension (arteriolar nephrosclerosis)
Medullary cystic kidney disease
Membranoproliferative GN I and GN II
Type 2 diabetes
Polymyositis (adult)
Prerenal azotemia
Primary amyloid
Pyelonephritis
Rapidly progressive (crescentic) glomerulonephritis
Secondary systemic amyloid
Thrombotic thrombocytopenic purpura
Wilms' tumor

What the risks are

Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins

Review Date:10/22/2007
Reviewed By:Robert Mushnick, M.D., Clinical Assistant Professor, Department of Nephrology, SUNY Downstate Health Center, Brooklyn, NY. Review provided by VeriMed Healthcare Network.

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