Alkaline phosphatase after sixty

This test reports how active alkaline phosphatase is in your blood, in u/l. Phosphatase is an enzyme that removes phosphate groups from other molecules. Almost every tissue makes its own version. The test adds all those versions together.

In adults two really matter. The bone version comes from osteoblasts, the cells that build new bone. The liver version comes from the small bile ducts. One result does not show which of the two has risen.

The value shifts upward over the years, and that is normal. Look at the bands from NUMBER, the national harmonisation project run by the NVKC.

The gap between the first and last rows is substantial. A woman of eighty has a ceiling more than twenty points above her reproductive years. Compare your result against a standard adult band and it will look raised. It is not.

Your own laboratory uses its own limits. Whatever your own report lists as normal is the figure that counts.

The question is always the same. Did the rise come from your bones, or from your bile ducts? Your doctor answers it with gamma-GT. That enzyme sits in the liver and not in bone.

If gamma-GT stays normal while this enzyme is raised, your doctor looks at your bones. In later life four causes come first.

The first is a vitamin D deficiency with osteomalacia as a result. Bone is then poorly mineralised and turnover speeds up. This is the most common and most correctable cause on the list.

The second is a healing fracture. Even a break from months ago can still lift the value.

The third is Paget's disease of bone. In that pattern the result is strongly raised while the rest of the panel stays normal. The condition mainly occurs after sixty and often runs for years without symptoms.

The fourth is medication. Long-term use of certain anti-epileptics raises both this enzyme and gamma-GT, through enzyme induction in the liver. That pattern looks like a bile-duct problem and is not one.

If gamma-GT climbs too, attention shifts to how bile is draining. Read the result then together with your ALT.

This test is a standard part of almost every liver panel. You usually meet it without having asked for it.

Having it done deliberately makes sense in four cases. With bone pain you cannot link to a fall or a known injury. When a vitamin D shortfall is known or suspected.

With long-term use of medication that loads the liver, including some anti-epileptics. And when monitoring a bone condition that has already been diagnosed.

Always request it together with gamma-GT. Without that second enzyme you cannot place a raised result. That leaves you holding a number with no direction.

A practical point in later life. Bring your medication list, including supplements and anything you have taken for years. Those long-running prescriptions are the ones nobody mentions any more. Sometimes they explain the whole pattern.

Fasting is usually not needed for this test. A fasting sample is still cleaner. The intestinal form of the enzyme rises after a fatty meal.