Water Consumption and Bathroom Usage

Hey everyone. I tend to drink a lot of water throughout the course of the day, including a protein shake before bed. I work out everyday either doing an hour on the treadmill or intense weight training with some cardio at the end. My question however deals with why on some days it seems like all the water I drink goes right through me, and on other days I barely need to use the bathroom at all. For instance, some days I need to go to the bathroom every half hour or so just because I've had so much water, whereas on some other days (even though I'm drinking the same amount) I barely need to go at all. For instance, 2 nights ago I probably got up to go to the bathroom about 3 or 4 times, whereas last night (with my water consumption being exactly the same) I didn't even get up once. Does anyone have any clue why this is happening?

did your activity or consumption level change? that might explain it...

Well the only difference I can think of is that yesterday in particular I just did cardio. I run in the morning and then in the afternoon I either do weights or run more. Yesterday I only ran more and didn't have to use the bathroom all night.

The thing is - I heard that weight training causes your muscles to retain water. Therefore, it doesn't make sense in my mind that on the day I DIDN'T weight train, I didn't go to the bathroom (since perhaps my muscles were retaining water)? I don't know, it doesn't make sense to me.

The same thing happens to me. I do not do much weight training but still retain water on days that I work out regardless of wether or not I do cardio or lifting. For example, yesterday evening, I drank 2 liters within an hour of going to bed and did not have to pee all night. But when I stepped on the scale this morning, it said that I gained 5 pounds yesterday, which we all know is not probable considering my 600 cal deficit. My only explanation is that my muscles retained most of the water I drank yesterday (because my salt intake was normal). Any other insight would be appreciated...GI JANE....MELKOR?

The water has to come out of you somehow... if you are working out hard enough to break a sweat, there goes a bunch of the water. If the air is particularly dry that day, there goes some more. If you are breathing hard even without sweating, you're breathing out more water vapour when you exhale. Your food contains water, and one day you might have more water-dense food than the next. And so on. It's not a fixed equation, there are hundreds of variables.

You have to be so careful with water consumption.... It's become fashionable for people to chug down litres and litres of the stuff whether they need to or not.  The idea that you should drink when you feel thirsty is often decried as 'you're already dehydrated when you feel thirsty!!! It's too late!!!!'    Which is silly when you think about it.   There's no benefit to the body in drinking more than you need and then all you end up doing is diving to the toilet all the time.  

And there's an even bigger caveat.  If you're drinking so much because you're very thirsty all the time and if you're waking up several times in the night to go to the toilet that could be symptomatic of Type II diabetes.... and then you'd be advised to see your doctor.  If you're drinking out of sheer habit and not because you're thirsty... maybe you should cut back on your water intake and wait until you feel a little thirsty as a cue to have a drink?