3 ms·5-HT is 5-hydroxytryptamine aka serotonin. 5-HTP is 5-Hydroxytryptophan, a precursor to 5-HT.by PragmaticPulp 4y ago5-HT is 5-hydroxytryptamine aka serotonin. 5-HTP is 5-Hydroxytryptophan, a precursor to 5-HT.hanniabu 4y agoYou're right, tried to delete after I realized I misread but HN wouldn't let mescns 4y ago5-HTP can be bought as a supplement.