GGT

Upper limits vary widely by lab, and many print a lower limit for women (around 40) than for men (around 70); use the range printed.

GGT is an enzyme found in the liver's bile ducts and in several other organs. It is a sensitive but non-specific marker: it rises with almost anything that irritates the liver, including alcohol and many medicines. The test measures the enzyme's activity in a blood sample.

Doctors use it mainly to work out whether a raised alkaline phosphatase is coming from the liver or from bone, since GGT rises with liver causes but not bone ones. It is also included in many private health screens and is followed by some people cutting down on alcohol.

• Alcohol, including regular moderate drinking
• Fatty liver linked to weight and diabetes
• Many medicines, including some epilepsy medicines, statins and antibiotics
• Bile duct blockage, including gallstones
• Viral hepatitis and other liver conditions
• Heart failure and some lung conditions

• It has no meaningful lower limit; low values are of no concern in the general population
• Some blood-pressure and cholesterol medicines lower it slightly
• Pregnancy, in the later months

• It stays raised for several weeks after a period of heavier drinking
• It is very commonly a little above range in the general population, particularly in men and in people who are overweight
• Lab upper limits differ two-fold, so flags are not comparable between labs

No fasting needed. It settles over four to six weeks after alcohol is stopped, so a repeat is often more useful than a single value.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.