There are no side effects for 5-HTP at safe doses. That is why I suggest starting at 50 or 100 mgs and increasing slowly. The high dose would be much more than 500 mgs.

WebMD:Other potential side effects of 5-HTP include heartburn, stomach pain, nausea, vomiting, diarrhea, drowsiness, sexual problems, and muscle problems. 5-HTP is POSSIBLY UNSAFE when taken by mouth in large doses. Doses from 6-10 grams daily have been linked to severe stomach problems and muscle spasms.

I do not recommend more than 500 mgs even though twice that is usually safe.