I played this game so much when I was younger but this was the one thing I could never figure out how to cure.

If there is a cure I would love to know. :)

A necromancer with grandmaster in achemy can mix potions to create a black potion of rejuvenation. You can easely find the different recipes online, just google "MM8 potion of rejuvenation". Alternatively this potion can be bought in high level shops. If you want to, you can save before entering a shop and if they don't sell it, reload until they do. The alchemist shop in Harecksburg on Regna island has a good chanche to sell it.

Thanks. :)

None of the classes I have are unable to be grandmasters in alchemy but at least I can buy the potions. :)

Recruit someone higher level (and of the appropriate class) and invest all their spent points in Alchemy. Then if need be take them around to the promotion quest givers and I think they can get experience for those quests even after they are done (note, memory here is really dodgy, I may be crazy). Level them until you can get GM alchemy, and just leave them stashed in the Adventurers Guild in Ravenshore until you need some potions made. It's not a smooth solution to the problem but this can work. Particularly when discussing some of the very high level characters.