Liver and pancreas · Blood

Alkaline phosphatase

An enzyme from the bile ducts and bone; raised when bile drainage is blocked or when bone formation is increased.

At a glance

Measured in blood
In 8 test panels
Check the preparation

Explanation

Alkaline phosphatase: what is measured?

Alkaline phosphatase (ALP) is an enzyme found mainly in the cells of the small bile ducts in the liver and in bone cells that make new bone. Smaller amounts come from the gut and, during pregnancy, from the placenta. The test measures the total of all these forms. A raised value can therefore come from the liver or from the bone; gamma-GT helps to make that distinction, because gamma-GT does rise with a bile duct problem and not with a bone cause.

What can it detect?

Blocked bile drainage (cholestasis) due to gallstones, a narrowing of the bile ducts or medicines
Increased bone formation: a healing fracture, Paget's disease, severe vitamin D deficiency (osteomalacia)
Liver disorders that mainly affect the bile ducts, such as primary biliary cholangitis
Rarely: a tumor of the bile ducts or metastases in the bone

Result

What does the result mean?

Alkaline phosphatase too high

A raised alkaline phosphatase often has a harmless explanation. In children and teenagers, the value is normally much higher than in adults because of growth, in the second half of pregnancy the value rises because of the placenta, and in people with blood group O or B the value can be somewhat higher after a fatty meal. With a healing fracture, the value is raised for months. If gamma-GT is also raised, the cause lies in the liver or bile ducts: gallstones blocking the bile duct, medicines (including some antibiotics and anabolic steroids) or inflammation of the bile ducts. Symptoms are then pain in the upper right abdomen, itching, jaundice and dark urine. If gamma-GT is normal, the enzyme usually comes from the bone: with a vitamin D deficiency or Paget's disease; symptoms are then bone pain or an increased risk of fractures. Rarely: metastases in the bone.

Alkaline phosphatase too low

A low alkaline phosphatase is rare and usually has no significance. It occurs with malnutrition, a zinc or magnesium deficiency, an underactive thyroid and with anemia due to severe deficiencies. In exceptional cases, a very low value may point to hypophosphatasia, a rare inherited bone disorder.

After an abnormal result

The GP assesses alkaline phosphatase together with gamma-GT, bilirubin and ALAT. If the combination points to the liver or bile ducts, an ultrasound of the upper abdomen usually follows; if it points to the bone, vitamin D, calcium and phosphate are measured and, if needed, the bone form of the enzyme. A slightly raised value without symptoms is first repeated after a few weeks.

Reliability

How reliable is the test?

Alkaline phosphatase points in a direction (liver or bone) but does not make a diagnosis. The value can only be interpreted together with gamma-GT, bilirubin and ALAT and with the person's age and situation. A slightly raised value in someone without symptoms is often temporary and, according to the Dutch GP guideline (NHG), is first repeated before any testing follows. With a persistently raised value and a normal gamma-GT, the laboratory can measure the bone form of the enzyme separately.

What can affect the result?

During growth (up to about 20 years of age) and in the second half of pregnancy, the value is normally raised; different reference values then apply.
A fatty meal shortly before the sample collection can raise the value slightly, especially with blood group O and B; a fasting blood draw makes the result more reliable.
A healing fracture or recent bone surgery raises the value for months.
Medicines such as anti-epileptic drugs, some antibiotics and anabolic steroids can raise the value; reference values differ per laboratory.

Preparation

Preferably do not eat for 12 hours before the sample is taken and drink only water. Also avoid an extra fatty meal the evening before: in some people the value is still higher the next morning after a fatty meal.

Who it is for

Who is the test useful for?

Useful for

Useful with symptoms that fit a bile duct problem (pain in the upper right abdomen, itching, jaundice), with bone pain or a suspected bone disorder, for monitoring a known liver or bone disease, and as part of a liver panel together with ALAT, gamma-GT and bilirubin. As a stand-alone test in healthy adults without symptoms, alkaline phosphatase has little value and a slightly raised result mainly leads to follow-up testing.

How common is it?

A slightly raised alkaline phosphatase without symptoms is fairly common and usually has a harmless cause. Gallstones, the most common serious cause of a raised value, occur in about 1 in 10 adults, more often in women and at older ages; most people with gallstones have no symptoms from them and a normal alkaline phosphatase. Paget's disease and bone metastases are rare.

NHG guideline on viral hepatitis and other liver disorders; Thuisarts.nl

Drawbacks and risks

A raised value due to growth, pregnancy or a healing fracture is easily mistaken for a liver or bone disease.

Get tested

Alkaline phosphatase: test panels

Alkaline phosphatase is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Alkaline Phosphatase (AF)
AF; liver and bone turnover.
€ 23,00
Blood draw
PhenoAge
PhenoAge Biological Age Test; determine your biological age with 9 standard blood values.
€ 85,00
Fingerstick
Alkaline Phosphatase (AF)
ALP; liver and bone turnover.
€ 23,00
Blood draw
Testosterone Replacement Therapy (TRT)
Testosterone, LH, FSH, Oestradiol, Prolactin, liver function, and blood values. For men with low testosterone or TRT monitoring.
€ 175,00
Blood draw
Liver
ALT, AST, Gamma-GT, alkaline phosphatase, and bilirubin. Assesses liver health in cases of alcohol use, medication, or liver complaints.
€ 58,00
Blood draw
Expanded: Testosterone Replacement Therapy (TRT)
Testosterone, LH, FSH, estradiol, prolactin, blood values, complete liver function, kidney function, and lipid profile.
€ 235,00
Blood draw
Supplemental: Testosterone Replacement Therapy (TRT)
Complete hormonal analysis with testosterone, DHEA-S, thyroid, blood count, liver function, kidney function, lipids, glucose, HbA1c, insulin, hs-CRP, vitamin D and ferritin.
€ 335,00
Blood draw
Whoop (Advanced Labs)
Comprehensive blood analysis with biomarkers that integrates directly with your WHOOP wearable for optimal performance and recovery.
€ 385,00

How reliable is the test?

Alkaline phosphatase