I don't experience this at all. If I've had too much NAC (more than 2-3 grams), I can smell it in urine, but that's all. Different people may metabolize it different ways, of course - and there may be variance in the available brands. I've had good experiences with GNC and 'NOW foods' NAC offerings (no personal preference between the two, and I'm sure there are other good quality brands out there).