Lab test glossary · Liver
Alkaline Phosphatase: what it means
Also known as: ALP, alk phos
Alkaline phosphatase is an enzyme from the liver, bile ducts, and bone; the pattern of change helps point to which of those is involved.
What it measures
Alkaline phosphatase (ALP) comes mainly from the liver and bile ducts and from bone. An elevation can therefore reflect a bile-flow issue or increased bone activity, and clinicians often use other tests to tell the two apart.
Typical range
Often roughly 40–130 U/L in adults, but normally higher in growing children and in pregnancy.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Bile-duct blockage or liver conditions
- Bone growth or healing, and some bone disorders
- Pregnancy (placental source)
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Uncommon; occasionally malnutrition or certain rare conditions
Why the trend matters
ALP is best interpreted in context and over time, since normal values shift with age, growth, and pregnancy.
When to talk to your doctor
A persistently high ALP is worth reviewing with your doctor, who may check whether it's coming from the liver or from bone.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.