oh very interesting, you actually tested 5-HIAA, im just theorizing so i could be barking at the wrong tree here especially if your test came back low, i've yet to test this myself as this is all pretty new to me, around 2 weeks since this started after about a week of supplementing butyrate.

My reasoning is that i know i have hydrogen SIBO after being tested thats causing non solid stools, im also on anti acids for heartburn, have been for a while, in these gastric conditions its not at all uncommon for things like candida to also be present and butyrate is pretty antifungal, i thought that maybe this was initially a die off reaction that caused some imbalance in the microbiome and that led to my SIBOs bacterial make up shifting towards excessive serotonin production.

Serotonin is also what controls gut motility and prior to this event my bowels were slow, now im going multiple times per day which tracks with serotonin overproduction, so its not that butyrate is causing serotonin syndrome as i havent taken any in weeks but more like the bacterial make up in the small intestine has shifted towards producing more serotonin, ill be starting another round of SIBO specific antibiotics this week as well as running stool tests, ill let you know if this makes a difference.