Alkaline phosphatases are a class of enzymes -- proteins that perform chemical reactions -- primarily found in the liver and bone. Damaged liver cells leak higher than normal levels of ALP into the blood. Your doctor may test the level of ALP in your blood to screen for liver function. Other health conditions can elevate ALP; your doctor will perform further tests to measure your liver function.
About Alkaline Phosphatase
Alkaline phosphatases remove phosphate groups from molecules in your body and only function in compartments that are alkaline, as opposed to acidic. ALP is used to deactivate other enzymes, recycle DNA and molecules used to store chemical energy, as well as in the digestion of drugs and nutrients.
Alkaline Phosphatase in the Body
ALP exists throughout the body, but levels are particularly high in the liver, kidneys, bile ducts, bone and the placenta in pregnant women. Dysfunction in any these organs, such as liver disease, bone disease or blocked bile ducts, can elevate ALP levels. You doctor can run an additional test to determine whether the elevated ALP originated from the bone or liver.
Liver Function
The liver performs a wide range of function in your body including detoxification and biosynthesis of enzymes and biochemicals. Your doctor will monitor your ALP levels as part of an overall liver panel if she suspects you may have liver disease. Symptoms of liver disease include weakness, loss of appetite, jaundice, nausea, abdominal swelling and dark urine.
The Test
ALP is measured by drawing a small amount of blood from a vein inside the elbow or on the back of the hand. Your doctor will instruct you not to eat or drink anything for six hours prior to the blood draw. Medications may affect the ALP test. Your doctor will issue specific direction regarding temporarily stopping medication. According to the National Institutes of Health, the normal range for ALP is 44 to 147 IU/L, although the range can vary according to laboratory, age range and gender. The reference range will be noted on your test results.
