An alkaline phosphatase (ALP) test measures the amount of the enzyme ALP in the blood. ALP is made mostly in the liver camera.gif and in bone with some made in the intestines and kidneys. It also is made by the placenta of a pregnant woman.
The liver makes more ALP than the other organs or the bones. Some conditions cause large amounts of ALP in the blood. These conditions include rapid bone growth (during puberty), bone disease (such as Paget’s disease or cancer that has spread to the bones), a disease that affects how much calcium is in the blood (hyperparathyroidism), vitamin D deficiency, or damaged liver cells.
Why It Is Done. A test for alkaline phosphatase (ALP) is done to:
Check for liver disease or damage to the liver. Symptoms of liver disease can include jaundice, belly pain, nausea, and vomiting. An ALP test may also be used to check the liver when medicines that can damage the liver are taken.
Check bone problems (sometimes found on X-rays), such as rickets, bone tumors, Paget’s disease, or too much of the hormone that controls bone growth (parathyroid hormone). The ALP level can be used to check how well treatment for Paget’s disease or a vitamin D deficiency is working.
How To Prepare. An alkaline phosphatase test is often done at the same time as a routine blood test. You do not need to do anything before having a routine blood test. If you are having a follow-up ALP test, you may be asked to not eat or drink for 10 hours before the test. The ALP level generally goes up after eating, especially after eating fatty foods.
How It Feels. The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
Risks. There is very little chance of a problem from having blood sample taken from a vein. You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.