Have mild nafld, where only ggt is elevated (didn't drink, but it was still around 120). will liver affect drug efficacy--how well i respond to drugs?

No: I'm actually wondering how the call was made if only GGT is up -- there's actually a genetic variant in which it tends to run quite high and these folks get accused of being drunks. Your liver should metabolize medications fine; if it's critical, an internist knows how to evaluate you. Your liver might also be asking for more physical exercise. Best wishes.