Serum creatinine

What is creatinine?

Creatinine is an important constituent of muscles and is broken down to creatinine. Creatinine can also be converted to ATP as a source of energy. The daily production of creatine and creatinine, depends on the muscle mass of an individual, and does not vary much. Creatinine is excreted from the body by the kidneys. Serum creatinine level remains constant and within normal range in normally functioning kidneys.

Why is the test done?

Serum creatinine level is used to test the functioning of the kidneys. In kidney diseases, the level rises and indicates renal damage. It is a more sensitive indicator of kidney function that blood urea.

How is it done?

The only preparation required is fasting for 6 hours before the test. Blood is drawn from a vein, usually from the inside of the elbow.

What are the normal values?

The usual values range from 0.8 to 1.4 mg/dl (milligrams per decilitre).

What are the abnormal results?

More-than-normal levels may be seen in:

• Kidney diseases – glomerulonephritis, renal failure, diabetic nephropathy, pyelonephritis, renal hypertension, etc
  
• Pre-eclampsia and eclampsia
  
• Urinary tract obstruction
  
• Hepatorenal syndrome
  
• Muscular dystrophy and muscle breakdown
  
• Reduced blood flow to the kidneys (dehydration, shock, heart failure)
  
• Certain drugs can increase creatinine measurements like aminoglycosides (gentamicin, amikacin, etc), heavy metal drugs (Cisplatin), and nephrotoxic drugs such as vancomycin, teicoplanin and amphotericin B.

Lower-than-normal levels may be seen in myaesthenia gravis or late stages of muscular dystrophy.