Taking 300-600mg of NAC daily is enough for most people to get benefits without side effects; higher doses don't help much more.

Efficacy of selenium and/or N-acetyl-cysteine for improving semen parameters in infertile men: a double-blind, placebo controlled, randomized study.

Investigation of the effect of N-acetylcysteine on serum levels of oxidative inflammatory biomarkers in patients with stroke