Alkaline phosphatase

What is alkaline phosphate?

Alkaline phosphatase is an enzyme, which is present in the blood, intestines, liver, and bones. The levels rise in liver damage or in growing bones. Children have higher levels than adults as their bones are in the growing phase. A variety of Alkaline Phosphatase is present in the placenta, hence values may be increased in pregnancy. A blood test is done to measure the enzyme alkaline phosphatase.

How is the test done?

Blood is drawn from a vein by venepuncture, usually from the inside of the elbow. The sample is usually taken after overnight fasting and sent to the laboratory for testing.

Why is it done?

This enzyme is raised in diseases of the liver, parathyroid glands, bone diseases and vitamin D deficiency. It is also be used to monitor patients on drugs which may harm the liver. It should not be relied on for a screening test because sometimes levels are high for unknown reasons and return to normal.

What are the normal values?

The normal values range from 20 to 140 IU/L (international units per litre).

What are the abnormal results?

More-than-normal levels may be seen in:

• Liver diseases especially the ones associated with obstruction of bile
  
• Bone diseases, healing fractures and rickets
  
• Leukaemia
  
• Hyperparathyroidism
  
• Chronic alcoholism
  
• Many drugs affect the level of blood level of alkaline phosphatase including antibiotics, hormones, analgesics, steroids, methyldopa, propranolol, allopurinol, tricyclic antidepressants, chlorpromazine, oral contraceptives, tranquillisers and oral anti-diabetics.

Less-than-normal levels may be seen in: