Not sure if a mod is causing it but ...

Drain health is just not showing up on enchantment or spell making alter lists, I've got minor wounds (also bought the higher versions) in my spell list and I can cast it.

I've got a lot of mods on but the only one that I think may have caused this is spell delete, but I have only ever deleted custom spells with it, I've also tried disabling it to see if it fixes anything, which didn't. All other spells work correctly.

Has anyone experienced problems with spells not showing up on the lists and knows how to fix it?

To be able to enchant certain effect you need to have this effect among your known spells and more, being able to cast it. If not the enchantment will not even show up in your list.

I thank you for your response but I did say that I have Minor Wound (which does the drain health effect) AND I can cast it.

You are right, sorry, I was (wrongly) certain minor wounds was from the damage health kind.

Edit: try deleting your minor wound spell and adding it again. maybe something got wrong with your's current one (I don't know for sure if the engine go first and only by the most basic or older spell or something like this).

Something that could confuse things if if some mod change this drain to damage or absorb, but this is just speculation, should not happen to vanilla spells.

Ok, turns out it was taken out by OOO (Oscuro's oblivion overhaul) mod.