Why get tested?
To screen for liver disease and/or alcohol abuse or to differentiate between liver and bone disease as a cause for elevated alkaline phosphatase (ALP)

When to get tested?
If your doctor thinks that you have symptoms of a liver disorder

Sample required?
A blood sample drawn from a vein in your arm

Note: GGT levels fall after meals, so it is best to be tested when you have not eaten for at least 8 hours.