What the value means
ALT (alanine aminotransferase) is released into the blood when liver cells are damaged. GGT (gamma-glutamyl transferase) relates mainly to the bile ducts and to strain on the liver, for example from alcohol. Some laboratories, such as those in Slovakia, report results in µkat/L (1 µkat/L corresponds to about 60 U/L), and upper limits vary by method and sex. Some experts propose lower ALT limits than laboratories usually use, because reference groups also include people with undiagnosed fatty liver. A value within the normal range is therefore not necessarily optimal – what matters is the trend over time and the context.
Possible causes
- Metabolic dysfunction-associated fatty liver (MASLD) – the most common cause; linked to abdominal fat, insulin resistance and higher triglycerides.
- Alcohol – typically raises GGT in particular, even with regular social drinking.
- Medicines and supplements – including some herbal extracts in high doses, such as green tea extract.
- Hard training before the test – ALT is also released from muscle.
- Viral hepatitis – hepatitis B or C can go unnoticed for a long time.
- Bile ducts and less common causes – gallstones, thyroid disorders, coeliac disease or iron overload.
What you can do
- Repeat the test – in 2–4 weeks, after at least a week without alcohol and 2–3 days without hard training.
- List everything you take – medicines and supplements, and show the list to your doctor; do not stop medicines on your own.
- Cut back on alcohol – with raised GGT, this is the first and most effective step.
- Weight loss – losing 7–10% of body weight clearly improves fatty liver.
- Activity and diet – regular exercise, fewer sugary drinks and refined carbohydrates; coffee is linked to better liver values in observational studies, but the evidence is only associative.
When to see a doctor
Discuss mildly raised values with your doctor, especially if they persist on repeat testing – they may suggest a liver ultrasound, hepatitis and iron tests, or a fibrosis score (FIB-4). Seek medical help promptly if you notice yellowing of the skin or eyes, dark urine, pale stools, pain under the right ribs, severe itching, or if values are several times above the upper limit.