One typically doesn't need to do anything in preparation for an alkaline phosphatase blood test since it's usually performed during a routine blood test, states WebMD. However, if the initial test results are inconclusive, the patient may be asked to fast for 10 hours before a follow-up test, notes Healthline.
Fasting before the test is recommended because eating generally causes alkaline phosphatase levels to go up, especially if the meal contains fatty foods, notes WebMD. Many medications can interfere with the alkaline phosphate levels of a patient. Therefore, individuals are advised to tell their doctors of any medications they are on before having the test done, according to MedlinePlus.
Alkaline phosphatase is an enzyme that is mostly produced in the liver and in the bones. Testing for ALP levels can, therefore, be used to diagnose liver or bone disease, check if treatments for these diseases are working, or as part of a routine liver function test, explains MedlinePlus.
The normal range for the alkaline phosphatase test is 44 to 147 international units per liter, although this may vary from one laboratory to another or by age and gender, states MedlinePlus. High levels of alkaline phosphatase may occur in pregnant women because of the ALP produced in the placenta, notes Healthline.