Explainer · updated 2026-11-09
GGT, explained in plain English
Key facts
- Typical adult reference interval in men: 11-55 U/L (HRI-HR)
- Typical adult reference interval in women: 9-35 U/L (HRI-HR)
- What GGT is: an enzyme from the bile ducts and the liver, used to settle whether a raised alkaline phosphatase came from the liver or bone (ACG 2017)
- Common reason behind a raised GGT: alcohol (ACG 2017)
What it is
GGT stands for gamma-glutamyl transferase. It is an enzyme from the bile ducts and the liver, and it is the usual way of settling whether a raised alkaline phosphatase came from the liver or from bone. It is sensitive to alcohol, which is much of its usefulness. It is measured in the blood.
What the number is telling you
The level is read beside alkaline phosphatase and the other liver results. Alcohol is the single biggest influence, and the level falls within weeks of cutting back.
What high or low can mean
High: A high GGT points at the bile ducts or the liver rather than at bone, and alcohol is a common reason behind it.
Low: A low figure carries no meaning on its own. What it rules out is a liver source for a raised alkaline phosphatase.
What a typical result looks like
Typical adult reference intervals from the HRI-HR set run from 11 to 55 U/L in men and 9 to 35 U/L in women. The range on your own report is the one that counts.
Questions worth asking your doctor
- Does my GGT suggest a liver source for my alkaline phosphatase?
- How much alcohol is behind this reading?
- What do my other liver results add?
- How does this compare with my previous results?
If a result worries you, ask your doctor.
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