I think that with Lipotrim you eliminate your carbohydrate stores so that you burn fat & go into ketosis. I don't know but the low water reading might relate to the amount of water that is usually bound to your carbohydrate stores.
I think that is why the initial weight loss is water & you have to be careful when re-feeding so that you don't put weight back on in fluid.
Anyway, if you are feeling good I wouldn't worry. If you are dehydrated you would not be peeing much, your skin and mouth would feel dry and you are likely to be constipated as well.