long and short of it
I've been finding conflicting advice on this matter so I figured I'd toss my five cents onto the proverbial google stack of coins. Whenever I use creatine I will inevitably begin urinating more at night. The more I take the more frequently I have to get up to take a leak. Even at a single gram I have to urinate at least twice before going to bed and once during the night. At five or six grams it can be as many times as four per night.
It's worth noting that I'm a vegetarian (well, mostly) so my need for creatine should be higher than people who eat meat on a daily basis. Despite this fact I cannot supplement with even a single gram. I'm also a complete non-responder to creatine so I was taking it mostly because the studies claim it helps. While I'm not doubting the studies I can tell you that mapping my progress cycling on, off, on and off again over the course of five months it was clear that creatine does absolute zero for my workout performance.
Here's some details about my life so you can see if it applies to you as well. I lift weights five days a week, monday to friday. I generally do heavy rest-pause workouts with 10 sets per exercise. Three to four exercises per day. I'm mentioning this to signal that I should be using the creatine in the ATP process but it just doesn't seem to do a thing. Except make me piss at night.
It takes a day or so after cycling off creatine for the urinating at night to stop and when it does it stops completely. This should underline that it isn't a physical problem with my body in general, it's directly related to my creatine intake. My fluid intake doesn't really change whether I'm on creatine or not either.
Hope it helps someone. You're not alone.