Ways of knowing you're not dehydrated is the color of your urine when you have to go. If your urine stays a dark yellow then you are, the lighter the color is your drinking enough to where your not. As commented talk to your Dr.

Dave all good stuff up there.
I have sleep apnea. I use my CPAP every night. My mouth gets dry too. But keep in mind that if you’re drinking too much at night, Full disclosure , stop drinking like 2hrs before bed. Or you might “need to go”,and not make it there soon enough. Happened to me 3 times. Fortunately, it was just a few dribbles, but for me that’s too much. Doing the 2 hr before bed is working for me.

Dehydration stresses the body which can trigger a seizure. As we age, dehydration becomes more of a problem. I have a designated cup with a lid and straw that I carry and keep with me no matter where I go. Maybe try to drink some Gatorade right before bed as that might help with the extra electrolytes in it. Also, try putting some Liquid IV in your water before bed. You can order that off of Amazon. Hope this helps! 👍😃

I’m tend to drink a lot of fluids at night and during the day. I think it depends on the person. My mom couldn’t drink a whole cup of water.

It fluctuates with me but not a prob, more a inconvenience to me, but no biggie, but thanks for your reply,