MECHANISM ENGINE
What Is GGT (Liver Enzyme)?
GGT sits on the same blood panel as ALT and gets far less attention, which is a shame, because it’s often the one that moves first. Worth knowing what it’s actually flagging before it becomes the number a GP wants to discuss.
The Overflow Pipe
If ALT is the smoke alarm for liver cell damage, GGT is more like the overflow pipe on a water tank, it tends to run first when the system’s under pressure, before things get bad enough to trip the main alarm. GGT rises with processing load on the liver, particularly from alcohol and certain toxins, but also tracks with the same fatty liver and metabolic strain picture that raises ALT. Seeing GGT move on its own, before ALT does, is often the earlier signal, the drip from the overflow before the tank’s actually full.
GGT, gamma-glutamyl transferase, is an enzyme involved in processing toxins in the liver, including alcohol. It’s particularly sensitive to alcohol intake and can rise even with moderate regular consumption. Like ALT, it’s also linked to non-alcoholic fatty liver disease and wider metabolic strain, and the two are often read together as part of the same liver function panel rather than in isolation.
NHS reference ranges for GGT are typically 8 to 61 units per litre for men and 5 to 36 for women, varying by lab; NICE guidance notes GGT as a sensitive, if non-specific, marker for liver processing load.
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Related mechanisms
Educational content only, not medical advice. Never stop or change medication without your GP’s supervision. Neil stopped his own medications in February 2024 on his own initiative and told his GP afterwards, with NHS blood tests to show. That is not the approach recommended here. Speak to your GP before changing your fasting pattern, diet, or medication.
What this is based on
NHS and NICE guidance, cross-referenced against Neil’s own NHS blood test record going back to April 2012. See the full timeline and current numbers.