ALP (Alkaline Phosphatase)
ALP is an enzyme present in liver, bile ducts, bones, and the placenta. Elevated ALP usually points to either liver/bile-duct disease or bone disease. The pattern of accompanying tests (GGT, calcium, bilirubin) tells your doctor which source is responsible.
Normal Range
Adults: 44–147 U/L (higher in growing children and pregnancy)
Reference ranges may vary slightly between laboratories. Always interpret your result in context with your doctor.
Why is ALP measured?
ALP is part of routine liver and bone panels. It is used to investigate suspected liver disease, bile duct obstruction, bone disorders such as Paget's disease or osteomalacia, and certain cancers.
High ALP means…
Elevated ALP combined with high GGT or bilirubin points to liver/bile duct cause. Elevated ALP with normal GGT and abnormal calcium points to bone cause. Mild elevation can be physiological in growing children, pregnancy (placental ALP), or after fractures (healing bone).
Low ALP means…
Low ALP is uncommon and may indicate zinc deficiency, malnutrition, hypothyroidism, or rare conditions like hypophosphatasia.
Symptoms associated with abnormal ALP
When ALP is high:
- Itchy skin (cholestasis)
- Yellowing of skin or eyes
- Pale stools, dark urine
- Bone pain (if bone source)
- Fatigue
When ALP is low:
- Often no symptoms
How to improve your ALP
- If GGT is also elevated, the source is liver/bile — investigate accordingly.
- If GGT is normal, suspect bone disease — check vitamin D, calcium, and consider a bone density scan.
- Vitamin D deficiency is a common cause of borderline-high ALP and is easily corrected.
Frequently asked questions about ALP
What does high ALP mean during pregnancy?
ALP rises in the third trimester due to placental production. It is a normal physiological change unless other liver markers are also abnormal.
Should children's ALP be higher than adults'?
Yes. Growing bones produce more ALP, so children and adolescents have ranges 2–3× the adult upper limit, peaking during growth spurts.
Medical Sources
This page is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider about your individual results.