Alkaline Phosphatase
Test OverviewAn alkaline phosphatase (ALP) test measures the amount
of the
enzyme ALP in the blood. ALP is made mostly in the
liver and in bone with some made in the
intestines and
kidneys. It also is made by the
placenta of a pregnant woman. The liver
makes more ALP than the other organs or the bones. Some conditions cause large
amounts of ALP in the blood. These conditions include rapid bone growth (during
puberty), bone disease (such as
Paget's disease or cancer that has spread to the bones), a disease that affects how much
calcium is in the blood (hyperparathyroidism), vitamin D deficiency, or damaged liver cells. If the ALP level is high, more tests may be done to find the
cause. The amounts of different types of ALP in the blood may be measured and used to determine whether a high level is from the liver or bones. This is called an alkaline phosphatase isoenzymes test. Why It Is DoneA test for alkaline phosphatase (ALP) is
done to: - Check for liver disease or damage to the liver.
Symptoms of liver disease can include
jaundice, belly pain, nausea, and vomiting. An ALP
test may also be used to check the liver when medicines that can damage the
liver are taken.
- Check bone problems (sometimes found on
X-rays), such as
rickets, bone tumors, Paget's disease,
or too much of the hormone that controls bone growth (parathyroid hormone). The ALP level can be used to check how well treatment for
Paget's disease or a vitamin D deficiency is working.
How To PrepareAn alkaline phosphatase test is often
done at the same time as a routine blood test. You do not need to do anything
before having a routine blood 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 eating fatty
foods. Many medicines may change the results of this test. Be sure
to tell your doctor about all the
nonprescription and prescription medicines you
take. Talk to your doctor about any concerns you have regarding the
need for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?). How It Is DoneThe health professional drawing your
blood will: - Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
alcohol.
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
blood.
- Remove the band from your arm when enough blood is
collected.
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure on the site and then put on a bandage.
How It FeelsThe blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch. RisksThere is very little chance of a problem from
having blood sample taken from a vein. - You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
minutes.
- In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.
ResultsAn alkaline phosphatase (ALP) test
measures the amount of the
enzyme ALP in the blood. NormalThe normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab. High values- Very high levels of ALP can be caused by
liver problems, such as
hepatitis, blockage of the bile ducts (obstructive
jaundice),
gallstones,
cirrhosis, liver cancer, or cancer that has spread
(metastasized) to the liver from another part of the body.
- High
ALP levels can be caused by bone diseases, such as
Paget's disease,
osteomalacia,
rickets, bone tumors, or tumors that have spread from
another part of the body to the bone, or by overactive
parathyroid glands (hyperparathyroidism). Normal
healing of a bone fracture can also raise ALP levels.
- Heart failure,
heart attack,
mononucleosis, or kidney cancer can raise ALP levels.
A serious infection that has spread through the body (sepsis) can
also raise ALP levels.
- Women in the third
trimester of pregnancy have high ALP levels because
the
placenta makes ALP.
Low valuesLow levels of ALP can be caused by: - Conditions that lead to malnutrition, such as
celiac disease.
- A lack of nutrients
in the diet.
- An inherited bone disease called hypophosphatasia.
What Affects the TestReasons you may not be able to
have the test or why the results may not be helpful include: - Taking medicines that may damage the liver,
such as some antibiotics, birth control pills, long-term aspirin use, and oral
diabetes medicines.
- Going through
menopause. Postmenopausal women may have higher ALP
levels than women who still have menstrual cycles.
- Your age.
Children normally have much higher ALP levels than adults because rapid bone
growth is normal in children and bones make ALP.
- Drinking a lot of
alcohol.
What To Think About- If the ALP level is high, other tests may be
done to determine whether a liver or bone problem is present.
- If liver disease is suspected, more blood tests, an
ultrasound, or a
CT scan are generally recommended to find the
problem.
- Other tests to check liver function, such as alanine
aminotransferase, aspartate aminotransferase, and bilirubin, may be done at
the same time as an alkaline phosphatase (ALP) test.
ReferencesCitations- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Other Works Consulted- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
CreditsByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Specialist Medical ReviewerAlan C. Dalkin, MD - Endocrinology Current as of:
May 3, 2017 Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins. Last modified on: 8 September 2017
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