I can't help but notice that I lose a lot of fluid when I do larger oral doses of DMT. I will get up 2-3-4 times and take fairly large pee. One of my friends that I shared some with wasnt so lucky and actually soaked my couch, and he specifically avoided eating/drinking anything for a few hours before. At first I thought it was just the experience being messed with while under the effect of DMT but that doesn't seem to be the case. When its all done I almost always have a dry mouth and want something to drink. Is this common, what is the cause?

If you are using harmala alkaloids to activate your oral DMT then this may explain what you describe; harmalas via rue are sometimes used to promote diuresis by some people in the Middle East, amongst other uses.

psilocybe mushrooms and any mix of beta carbolines/DMT does this to me..I think mescaline does as well..

I have a tendency to get dehydrated fairly easily. What I have found is that paying particular attention to the water I consume makes a difference. We are after all made up mostly of water.I will pre/post usually with coconut water, it is a good source of the electrolyte potassium. For "regular" water I try to stick to water that at the min goes through reverse osmosis, although ozonation and uv light are preferable. This also gives some peace of mind that you are not ingesting the general populations' medications, however minute in quantity. I won't mention by name exactly what I take to keep my electrolytes in balance but stay away from sweetener over-loaders like g-torade and the like.