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Thanks for contacting with your health concern
1. I have following opinion on the query which you can consult with your attending doctor/ Hepatologist:
i. GGT [gamma glutamyl transferase] is the most sensitive indicator of hepatobiliary disorders. Though elevated in hepatocellular damage, it is rather non-specific because elevated GGT level may be found in pancreatic, renal, cardiac or pulmonary disorders. 
PS. GGT is a potential marker of 
alcohol abuse and is raised in hepatocellular damage and 
cholestasis. [please let me know about alcohol intake] and may be used to determine the cause of elevated 
alkaline phosphatase (ALP] levels also. 
2. The GGT test can diagnose 
liver damage, but it can't determine the cause, so if your GGT level is elevated, you'll probably have to undergo more tests.
PS. and because although is sensitive but are very nonspecific and serve to detect liver disease rather than quantitative liver function so their high values don't signify a serious complication most of the time, it is the underlying pathophysiological process which needs to be diagnosed and managed, so if constantly on the higher side, go with  
serum albumin, PT [prothrombin time] and INR.
3. Several studies have shown that 
blood donation or phlebotomy reduces GGT and other risk markers associated with liver diseases and 
insulin resistance. Interestingly, moderate to high coffee consumption has been universally shown to reduce GGT.