I take 4000mg of the Vitamin Shoppe brand of MSM powder. I didnt have headaches or tiredness at all. I started by taking 1/4 tsp then gradually increased it to 1 tsp/day. I take it at night before bed. I've been taking it for approx 3 months now and I have had maybe 2-3 pimples since beginning MSM but they are gone within 2 days or so. My skin glows now and my pores have drastically reduced. I cant really say what the benefits to my hair have been because I also take other supplements, but I know for sure that my skin did not improve until I began the MSM. I also drink 64+ oz of water/day.