hello, are you talking about gamma glutamyl transpeptidase
estimation which is increased in biliary duct damage in liver involvement . I think your doctor might be thinking of viral hepatitis
. as far as your MCV of re dblood cells are concerned they may increase id vit b 12 or b6 or folic acid deficiency
or even in alcoholic liver disease
where gama is also elevated , so quit alcohol only if you consumes it and be honest to your treating doctor and you should ask them clearly about your dought after an all doctors are there to help you.
an another gamma test is done for gamma globulin
estimation to detect several infections.
I think you should follow and believe your treating physician and leave all worry and try to recover fast.
wish you all the best.