M2 is better than Viagra for rock hard erections. Increases female libido too... being that my girlfriend is a pale irish redhead, she loves the stuff as it helps her to not burn so easily and actually tan. It can also have an appetite suppressant effect to it, and as heavy stated, if you take too large a dose, you may get nauseated... for me, this was 3000mcg+ (def not needed by any means, just testing the waters per say, it's quite effective at 500mcg for most men), while for my girlfriend it was anything more than 200mcg and she'd feel nauseous.