Several caveats must be remembered in interpreting ALP results:ALP levels should always be measured after fasting because enzyme levels increase as much as 30 U/L after food ingestion. Patients with blood group O and B who are secretors can have increased ALP levels after eating a fatty meal because of the release of intestinal enzyme.African Americans have 10 to 15% higher ALP serum levels than Caucasians.In children, ALP is increased up to 3 times the upper limit of normal and in pregnant patients it can be increased up to 2 times normal.