Alkaline phosphatase test: ALP normal range, high and low results

An alkaline phosphatase test measures ALP, an enzyme that comes mainly from the liver's bile ducts and from bone. A high result says that one of those two, or both, is more active than usual, and the test alone cannot tell which. Doctors find out by reading it with GGT and the other liver markers.

What ALP measures

ALP is an enzyme found in most tissues, with the highest amounts in the liver, bile ducts and bone. Each tissue makes its own form. Smaller amounts come from the intestine, kidney and white cells, and in pregnancy the placenta adds its own.

In the liver, ALP rises when bile does not flow freely, because any blockage in the bile ducts makes the liver produce more of it. In bone it comes from osteoblasts, the cells that lay down new bone, so it rises whenever bone is being built or remodelled quickly, as it is in growing children.

ALP normal range

ALP is reported in units per litre (U/L, also written IU/L). Ranges depend heavily on age, because growing bones make a lot of ALP:

Group	Reference range
Adults, UK harmonised range (Pathology Harmony)	30 to 130 U/L
Men aged 19 and over (Mayo Clinic Laboratories)	40 to 129 U/L
Women aged 17 and over (Mayo Clinic Laboratories)	35 to 104 U/L
Children aged 1 to 9 (Mayo Clinic Laboratories)	142 to 335 U/L
Boys aged 13 and 14 (Mayo Clinic Laboratories)	116 to 468 U/L
Girls aged 13 and 14 (Mayo Clinic Laboratories)	57 to 254 U/L

Mayo Clinic Laboratories warns that results in children and teenagers must be read against age-specific ranges. Pregnancy raises ALP as well. Ranges also vary by laboratory and method, so the range printed on your own report is the one to read against.

What a high ALP usually points to

From the liver

When ALP and GGT rise together, the source is very likely the liver, and the pattern points to cholestasis: bile not draining as it should. Causes include gallstones or a narrowing that blocks a duct, conditions of the bile ducts themselves such as primary biliary cholangitis and primary sclerosing cholangitis, congestion of the liver, and reactions to medicines. Rises tend to be larger, often more than four times the upper limit, when a duct outside the liver is blocked. Conditions that inflame liver cells, such as viral hepatitis, usually lift ALP less than three times the limit, or not at all.

From bone

A high ALP with a normal GGT points towards bone. That covers ordinary reasons, such as growth in children and teenagers and a healing fracture, and conditions a doctor would want to look at, such as Paget's disease of bone, an overactive parathyroid gland, and rickets or osteomalacia (softened bone, often linked to low vitamin D). The British Society of Gastroenterology notes that an isolated raised ALP may come from vitamin D deficiency rather than the liver.

What a doctor typically looks at next

GGT is the usual starting point: it rises with liver ALP but not with bone ALP, because bone holds no GGT. ALT, AST and bilirubin fill in the liver side. For bone causes, a doctor may look at calcium, phosphorus and 25-OH Vitamin D, since the bone conditions above involve them. If the source is still unclear, an ALP isoenzyme test can separate the liver and bone forms, though it is not offered everywhere, and an ultrasound looks at the bile ducts directly.

A low ALP

A low ALP is less common. MedlinePlus lists zinc or protein deficiency, malnutrition, pernicious anaemia, thyroid disease, Wilson disease and hypophosphatasia, a rare inherited condition of bone and teeth, among the possible reasons. Birth control pills and some other medicines can also lower it.

What moves ALP

• Age and growth. Children and teenagers run high because their bones are growing.
• Pregnancy. The placenta makes its own ALP, so levels rise.
• A fatty meal. MedlinePlus notes that eating a fatty meal before the test can cause a small increase.
• Medicines. Birth control pills and some other medicines lower ALP; others raise it.
• Healing fractures, while new bone is being laid down.
• Exercise. Unlike ALT and AST, ALP stayed within the normal range after a hard weightlifting session in healthy men.
• Ramadan fasting. A 2021 review of ten studies with ALP data found a small fall across Ramadan in healthy adults.
• The sample. Burst red cells in the tube (haemolysis) can push ALP down, and Mayo Clinic Laboratories rejects grossly haemolysed samples.

Preparing for the test

ALP is usually ordered with other blood tests that need fasting for several hours, and fasting also avoids the small rise a fatty meal can cause. Tell the person taking the sample if you are pregnant, have had a recent fracture, or take any medicines, including birth control pills. MedlinePlus advises against stopping any medicine unless your doctor tells you to.

How Clare's panel handles ALP

Clare's panel includes ALP, measured by the lab. It is drawn with GGT, so the liver-or-bone question can be read from the same sample, and with calcium, phosphorus and 25-OH Vitamin D for the bone side.

ALP and vitamin D in the UAE

Low vitamin D is common in the UAE, and it is one reason an ALP can rise without any liver problem. In an Abu Dhabi study of 12,346 Emirati adults screened in 2011 and 2012, 72 per cent had 25-OH vitamin D below 50 nmol/L, and 4.1 per cent reached the 75 nmol/L the study counted as normal. When vitamin D stays low for long enough to soften bone, as osteomalacia in adults or rickets in children, ALP goes up with the extra bone-building activity. That makes 25-OH Vitamin D a natural result to read beside an isolated high ALP. Our article on vitamin D in the UAE explains why levels run low in such a sunny country.

Price

ALP is usually sold within a liver function test. When we read public prices on 11 October 2026, a liver function test cost from 89 to 1,100 at six UAE providers. The top figure was a wider package that adds a hepatitis B test; the five standard liver panels ran from 89 to 199. Most listings did not say whether VAT was included, and home collection can add a fee: one lab charged for it on smaller orders.

Related tests

ALP is one part of the Liver function test. Read it with Gamma-Glutamyl Transferase (GGT), which separates liver ALP from bone ALP; 25-OH Vitamin D, for the bone side; and Calcium, the mineral that bone turnover and vitamin D both act on.

Why ALP means more over time

ALP stayed within the normal range after hard exercise in the weightlifting study, so a change between two tests is less likely to be noise from training than it is for ALT or AST. In adults, an ALP that climbs from one test to the next, especially with GGT climbing beside it, is worth raising with a doctor, while a raised ALP that comes back down as vitamin D recovers tells its own story. In children and teenagers, the direction is read against the age ranges as they grow. When Clare opens, each member's results will sit in one health account, with each marker's trend over time.

Clare is opening with a waitlist at clare.health.