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Alkaline Phosphatase
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Alkaline phosphatase (ALP) is an enzyme measured in a routine blood sample, most of which comes from your liver, bile ducts, and bones. In adults, a typical serum ALP result falls in the range of about 44 to 147 U/L, though your own lab's reference range is what matters most.
Group | Typical range | Units |
|---|---|---|
Adults | 44 to 147 | U/L |
Ranges vary between labs and are higher in children and pregnancy, so compare to the range on your own lab report.
What alkaline phosphatase measures
ALP is an enzyme that speeds up chemical reactions in your body, and it is concentrated in the cells lining your liver's bile ducts and in bone-building cells. Because it comes from more than one tissue, an ALP result reflects a mix of liver and bone activity. Clinicians usually read it as part of a liver panel or comprehensive metabolic panel rather than on its own.
What high or low levels mean
A high ALP most often points to your liver and bile ducts, such as a blocked or inflamed bile duct (cholestasis), gallstones, or hepatitis. It can also rise with normal or accelerated bone activity, including childhood growth, a healing fracture, or Paget disease, and it climbs naturally during pregnancy because the placenta makes ALP. Low ALP is uncommon and can be linked to malnutrition, zinc or vitamin B6 deficiency, an underactive thyroid, or rare inherited conditions. Because ALP arises from both liver and bone, your clinician often orders companion tests such as GGT, bilirubin, and other liver enzymes to pinpoint the source. Persistent abnormal results, or ones paired with jaundice, itching, or pain, warrant follow-up.
Alkaline phosphatase FAQ
What does it mean if your alkaline phosphatase is high?
A raised ALP usually reflects your liver or bile ducts, such as a blockage or inflammation, or increased bone turnover from growth, healing, or bone disease. Pregnancy also raises it.
Should you worry about slightly elevated ALP?
A mildly high value is often harmless and can reflect bone growth or a recent fracture. Your clinician looks at trends and companion tests before deciding whether further evaluation is needed.
What is the difference between ALP and GGT?
GGT is more specific to your liver and bile ducts, so pairing it with ALP helps show whether a raised ALP is coming from your liver or from bone.
Read alongside your alanine aminotransferase, aspartate aminotransferase, and total bilirubin results for a fuller picture of liver health.
Sources
MedlinePlus Medical Encyclopedia. ALP blood test. U.S. National Library of Medicine.
MedlinePlus Medical Test. Alkaline Phosphatase.
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