Alkaline Phosphatase (ALP): About This Test

What is it?

An alkaline phosphatase (ALP) test measures the amount of the enzyme ALP in your blood. ALP is made mostly in the liver and in bone, with some made in the intestines and kidneys.

Why is this test done?

The ALP test is done to:

• Check for liver damage when you're taking medicines that can damage the liver.
• Help look for liver disease. Liver disease may cause symptoms. These may include pain in the upper belly, nausea, vomiting, and sometimes jaundice.
• Check for bone problems (sometimes found on X-rays). Some examples are rickets, osteomalacia, bone tumors, and Paget's disease. The test can also check for too much parathyroid hormone. This is the hormone that controls bone growth.
• Check to see how well treatment for Paget's disease or a vitamin D deficiency is working.

How do you prepare for the 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 you eat fatty foods.
• Tell your doctor ALL the medicines, vitamins, supplements, and herbal remedies you take. Some may increase the risk of problems during your test. Your doctor will tell you if you should stop taking any of them before the test and how soon to do it.

How is the test done?

A health professional uses a needle to take a blood sample, usually from the arm.

How long does the test take?

The test will take a few minutes.

What happens after the test?

• You will probably be able to go home right away. It depends on the reason for the test.
• You can go back to your usual activities right away.
• If the ALP level is high, other tests may be done to see if you have a liver or bone problem.
• If your doctor thinks you might have liver disease, you may need more blood tests, an ultrasound, or a CT scan.