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Liver function can be measured with various tests. One of the most sensitive ones is GT, or gamma-glutamyltransferase (S-Gt). It is normally found in high levels in the wall cells of the liver and bile duct. GT often rapidly changes in connection with diseases of the liver and obstructions of the bile duct.

GT also occurs in the kidneys, pancreas, and gut. Renal GT mainly occurs in urine.

When should GT be measured?

GT levels should be checked when suspecting excessive alcohol consumption and in conjunction with liver diseases and symptoms suggesting obstructions of the bile duct:

  • Yellowness of the skin
  • Sudden pain in the right upper or central abdomen
  • Nausea
  • Fatigue
  • Slight increase in body temperature
  • Loss of appetite
  • Feeling of pressure in the upper abdomen
  • Itching of the skin
  • Decreased muscle strength
  • Problems concentrating
  • Decreased memory function
What does the GT test measure?

The test measures the level of the GT enzyme. The blood test indicates whether the level of the GT enzyme is within the normal reference range. An elevated value typically indicates liver damage or obstruction of the bile duct, but the test does not give the reason for it.

One significant reason can be alcohol. In fact, the GT level is used in determining excessive alcohol consumption. Heavy drinking on one night does not have an effect on the GT level, but long-term high alcohol consumption can be seen as an increase in GT. The GT value normalises within a few weeks of stopping alcohol use.

Normally, the result is: 

Reference values:

  • Men: <60 U/l
  • Women: <40 U/l
  • Children

under 15 days 23 – 219 U/l 15 days to 11 months 8 – 127 U/l 1 - 10 years 6 – 16 U/l 11 - 17 years 7 – 21 U/l

In investigations, other tests measuring liver function should also be done besides the GT test, such as alkaline phosphatase (S-AFOS), alanine aminotransferase (S-ALAT), and bilirubin (S-Bil).

As an indicator of high alcohol consumption, serum carbohydrate-deficient transferrin (S-CDT) should be examined to clarify the situation.

Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.

Elevated GT levels are caused by:

  • Obstruction of the bile duct
  • Liver tumours when the passage of bile is blocked
  • Excessive alcohol consumption and resulting fatty liver, liver cirrhosis, or chronic hepatitis
  • Hepatitis (liver infection)
  • Certain medicinal agents (e.g., antiepileptics, antidepressants)
  • Pancreatitis
  • Myocardial and pulmonary infarction
  • Pneumonia
  • Heart failure
  • Ulcerative colitis
  • Obesity

Subnormal GT values have no clinical significance.

  • Alkaline phosphatase is elevated in liver and bone diseases (1046 S-AFOS)
  • Bilirubin is formed by the breakdown of red blood cells and is a test for liver and bile duct diseases (1185 S-Bil)
  • Alanine aminotransferase, indicator of liver cell damage (1026 S-ALAT)
  • Aspartate aminotransferase reacts quickly to liver, cardiac muscle, and musculoskeletal cell damage (1128 S-ASAT)
  • Carbohydrate-deficient transferrin is a good indicator of high alcohol consumption (S-CDT)

SYNLAB test list: Gamma-glutamyl transferase (1489 S-GT, 4597 P-GT)  https://www2.synlab.fi/laboratoriokasikirja/tutkimuskuvaukset/gt/

SYNLAB: Gamma-glutamyl transferasehttps://www.yml.fi/tuotekuvaus_show.php?tuotenro=144

Terveyskirjasto health library: Glutamyylitransferaasi (P-GT) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk03073&p_hakusana=glutamyylitransferaasi https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=ltt00981&p_hakusana=glutamyylitransferaasi

Potilaan lääkärilehti (Patient's Medical Journal): GT on alkoholin suurkulutuksen laboratoriomittari https://www.potilaanlaakarilehti.fi/uutiset/gt-on-alkoholin-suurkulutuksen-laboratoriomittari/

Lab Test online: Gamma-glutamyl transferase (GGT) https://labtestsonline.org.uk/tests/gamma-glutamyl-transferase-ggt-test


Fasting is not required

This examination does not require fasting