Did you work up to that dose gradually or did you start off that high? Most herbalists and naturopaths recommend starting 5-HTP at 50 mg and gradually working up. Just like prescription SSRIs, 5-HTP can cause nausea when titrated too rapidly.
I used to recommend it to clients with depression who preferred to try supplements before starting SSRIs. I always instructed them to start at 50 mg and increase by 50 mg every 5-7 days until reaching a max of 200 mg and to stop increasing the dose if they experienced nausea. A few were able to tolerate a higher dose, but most stopped at 200 mg per day.
The theory behind why 5-HTP can help migraine is sound, but little research has been done proving its effectiveness. It is good to hear that it helps you. I would just urge caution and suggest much slower titration to reduce the risk of nausea and vomiting.
Tammy Rome
Herbalist & Licensed therapist