I'm very often dehydrated as well, and I almost never feel thirsty. I also can't often tell what colour my urine is, since I rarely JUST pee. Yknow. Once, my doc told me I should just try to have a drink of water every time I go to the bathroom. Not always practical, but a good rule of thumb I follow whenever I can.
One thing I was thinking of trying is a private hydration clinic. There's one in my city, and I think it's becoming somewhat trendy, mostly for people who want "vitamin" infusions and quick hangover cures. But after a recent dehydration crisis that landed me in Emerg, I've thought about contacting them, and finding out what their facilities are, if they have RNs on staff to insert IVs or whatever. I figure, if it's affordable, it might save me some aggravation (not to mention exposure to all the nasties in hospital ERs!)
Onward!
KS