I've used about 6 different brands and countless mk677 runs over the last couple years: never had issues with headaches, the very first couple days of one brand in particular I would have an increased body temp but it went down after a bit...I have ran into stuffy nose issues while on it and have heard of other guys experiencing the same thing but not exactly sure of the scientific reason. What dose are you running it at? I would run into more problems at 25MG so I cut it in half to 12.5MG. Also you could try switching the timing, some people experience more or less sides if they dose it in the AM or PM. You could also go 5 days on 2 days off, that would possibly mitigate some sides as well.