Both are serotonin precursors and combining them may excessively elevate serotonin.
5-HTP and L-tryptophan both convert to serotonin through the same pathway, with 5-HTP being one step closer.
Generally unnecessary to take both. Choose one, and do not combine with SSRIs or other serotonergic drugs.
Known drug category interactions for these supplements. Especially relevant if you take prescription medications.
Combining 5-HTP with SSRIs can cause serotonin syndrome.
NEVER combine 5-HTP with SSRIs, SNRIs, MAOIs, or tramadol without direct medical supervision.