For me it's been Magnesium, Harmalas seem to deplete Magnesium, i'm not sure if it depletes/uses up anything else, but consistently since i've been taking Harmalas (since 2012) i've noticed that it will use up/deplete my Magnesium and i'll start getting cramps (especially leg cramps) and maybe some heart palpitations.
Supplementing with a good form of Magnesium (for me Magnesium Glycinate, 300mgs to 400mgs a day) seems to help and after a few days all the cramping and heart palpitations will go away. Also as Mitakuye said, might want to make sure of Potassium levels as well, i haven't tried supplementing with Potassium much (though i probably should) but i do try to get some through my diet though it's probably not enough, but for me Magnesium definitely solves the issue. I haven't particularly noticed cramps during an experience but since i dose Harmalas on a regular basis i do notice them in the day to day when i'm low in Magnesium.
Only other thing i'd say is to take the Magnesium or other things either first thing in the morning maybe, or preferably right before bed, taking them at the same time or like right before Harmalas+DMT ime may not work out so well.
Heck one time i tried supplementing with Magnesium Oxide (which sucks btw) and Zinc Gluconate (which also sucks btw) for a few days or so and had like taken it before, as well as with my Harmalas and DMT, and the Zinc consistently gave me this effect with the DMT in the mix of a kind of "ramping up" buzzing radio staticky jolt-like effect/feeling which freaked me tf out every time it happened, it was rather jarring and while i'm not sure if it's unsafe it didn't feel healthy, and the Magnesium Oxide strangely enough (not sure if it was it in itself or the combination of it and Zinc) would give me this like chest pain/pressure and freakish heart palpitations and let me tell ya, experiencing that along with the "Zinc Zaps" as i call them (which are definitely a different kind of zap compared to the "brain zaps" most people talk about which i've also experienced from Harmalas+DMT back in my early days and those were actually very pleasant compared to the Zinc Zaps lol) is rather freaky and scary and it definitely steered me away from taking them at least at the same time as Harmalas+DMT, definitely don't want to ever feel that stuff again, my heart literally felt like it was about to burst out of my chest and i was going to have a heart attack or something, idk wtf that was about but i'm glad i was okay after that.
Also i used to drink dark chocolate almond milk before they removed the sugar and now it tastes like crap imo, and back then they had Zinc Gluconate in the almond milk, i'm not sure of the dosage, it seemed rather low but definitely still noticed the exact same Zinc Zaps if i drank it while on Harmalas+DMT, just to a lesser degree than the 25 to 50mgs of Zinc Gluconate i had been supplementing with.
But yeah i've consumed some Magnesium first thing in the morning, as well as before bed, and it hasn't been any issue.