An alkaline phosphatase level test (ALP test) measures the amount of alkaline phosphatase enzyme in your bloodstream. The test requires a simple blood draw and is often a routine part of other blood tests.
Abnormal levels of ALP in your blood most often indicate a problem with your liver, gallbladder, or bones. However, they may also indicate malnutrition, kidney cancer tumors, intestinal issues, a pancreas problem, or a serious infection. The normal range of ALP varies from person to person and depends on your age, blood type, gender, and whether you’re pregnant.
According to the University of California San Francisco (UCSF), the normal range for serum ALP level is 20–140 IU/L, but this can vary from laboratory to laboratory. The normal range runs higher in children and decreases with age. The best way to know what is normal or not is to discuss the results with your doctor, who will be able to interpret the lab’s specific result and reference ranges.
What is alkaline phosphatase?
Alkaline phosphatase is an enzyme found in your bloodstream. ALP helps break down proteins in the body and exists in different forms, depending on where it originates. Your liver is one of the main sources of ALP, but some is also made in your bones, intestines, pancreas, and kidneys. In pregnant women, ALP is made in the placenta.
An ALP test may be performed to determine how well your liver and gallbladder are functioning or to identify problems with your bones.
Liver and gallbladder
Checking ALP levels in the blood is a routine part of liver function and gallbladder tests. Symptoms such as jaundice (yellowing of the skin and eyes), abdominal pain, nausea, and vomiting may lead your doctor to suspect there is something wrong with your liver or gallbladder.
The ALP test can be helpful in identifying conditions such as:
- hepatitis (inflammation of the liver that could be due to an infectious or noninfectious cause)
- cirrhosis (scarring of the liver)
- cholecystitis (inflammation of the gallbladder)
- blockage of bile ducts (from a gallstone, inflammation, or cancer)
You may also need an ALP test if you’re taking a medication that has the potential to damage your liver, such as acetaminophen (Tylenol). Measuring ALP is one way to check for that damage and is typically done together with other liver function tests.
The ALP test can be helpful in the diagnosis of bone problems such as:
- rickets: a weakening or softening of the bones in children that’s most commonly due to a significant deficiency of vitamin D or calcium
- osteomalacia: a softening of the bones in adults usually due to significant vitamin D deficiency, but also possibly due to the body’s inability to process and utilize vitamin D properly
- Paget’s disease of the bone: a disorder causing major problems with bone destruction and regrowth
ALP testing may also be helpful in investigating the presence of cancer tumors, unusual bone growth, or vitamin D deficiency. It can also be used to check the progress of treatment for any of the above conditions.
Having blood drawn for an ALP test is routine. It’s usually combined with other liver and kidney function tests. You may have to fast for 10 to 12 hours prior to the test. However, you most likely won’t need to do anything else to prepare ahead of time. If the results of the test are inconclusive, your doctor may order a follow-up test.
Eating can interfere with your ALP levels. Medications can also change your ALP levels; be sure to tell your doctor about any medicines you are taking.
An ALP test requires a health professional to draw a small sample of blood from your arm. This will be done in your doctor’s office or in a clinical lab. The doctor or nurse will clean the skin on the front side of your elbow with an antiseptic and apply an elastic band to allow blood to pool in the vein. They will then insert a needle into the vein to draw blood into a small tube. The process is quick and causes little pain or discomfort.
There are very few risks associated with having your blood drawn. You may experience some bruising around the puncture site, but this can be avoided by putting pressure on the wound. In rare cases, phlebitis (inflammation of the vein) may develop. If you experience this complication, apply a warm compress until the swelling goes down. Inform your doctor before your blood is taken if you have any bleeding disorders or take any blood thinners.
When the results of your ALP test are in, your doctor will discuss them with you and tell you what to do next.
Higher than normal levels of ALP in your blood may indicate a problem with your liver or gallbladder. This could include hepatitis (liver inflammation), cirrhosis (liver scarring), liver cancer, gallstones, or a blockage in your bile ducts.
High levels may also indicate an issue related to the bones such as rickets, Paget’s disease, bone cancer, or an overactive parathyroid gland. In rare cases, high ALP levels can indicate heart failure, kidney cancer, other cancer, mononucleosis, or bacterial infection.
Having lower than normal ALP levels in your blood is rare, but can indicate malnutrition, which could be caused by celiac disease or a deficiency in certain vitamins and minerals.