Start with a small glass, remembering that it's a probiotic elixir, and go upwards from that, by intuition. It all depends on your situation and no one knows you better than you know yourself. :-) Once I drank more than a bottle (32 oz)in one day, because I'd made a batch that was so good, like a fine apple champagne, but better than anything alcoholic. (It is true that kombucha has a small amount of aclohol though.) It had brewed in the summer, and then had been sitting on the veranda through winter in an insulated cooler. Some of the bottles broke when fermentation continued, but a few were intact. Wow, it was good. But I was literally buzzing, all night. It wasn't terrible, exactly, but I wouldn't recommend it...
anyway, i'm sure that's a rare event. I felt great after the buzz wore off. lots of energy.