What could cause the urgent and frequent need to urinate, especially at night or when trying to sleep?

I have been tested both for bladder infections and overactive bladder and the tests have been negative. I am only 20 years old. What could be causing this?

Assuming your doc has already ruled out diabetes (which I imagine they would have)... it might be something as simple as an imbalance in the hormones your body produces during the night. Your body produces a hormone called anti-diuretic hormone (or ADH) that tells your kidneys to slow down and not excrete as much water from your system when your body needs to conserve water. Normally, this hormone is released automatically at night, which is why most people can sleep for 8 hours without needing to urinate even though they couldn't go nearly that long without urinating during the daytime. It could just be that your body for whatever reason isn't releasing enough ADH at night (or maybe even reversing the nighttime and daytime cycles), so that your kidneys just keep churning out urine during the night and it's more than your bladder can handle. (In children this is thought to be a frequent cause of bed-wetting, but even if you're waking up in time to go to the bathroom and avoid wetting the bed, you could still have the same basic problem.)

Ask your doctor about this... if that might be what's going on, there's a synthetic version of ADH that you might be able to take at night to reduce the symptoms and help you sleep better. This isn't the only possibility, but it might be worth considering. Good luck!

You could have diabetes or a thyroid problem. You probably should get checked for both of those asap.

you might be diabetic. get checked out.

You are pregnant my dear...

you could have sugar diabetes or maybe a yeast infection or it could be just all between the ears just thinking you need to go.if you were male i would say you have prostate problems
. Have they checked your kidneys yet for infection ???

you're probably not pregnant. lol. (urinating frequently is only common in the last few months of a pregnancy when the baby is resting on the bladder)
Try limiting how much liquid you drink in the 3 or so hours before bed.
Unless you are talking about just the "need" to urinate, and when you try, nothing or little comes out. In this case, try the reverse. Drink -alot- of water. It will help flush out anything in your system. I used to have this problem whenever I went to a certain restraunt. I assumed it was something in my head and if I distracted myself enough not to think about it, the feeling passed. Try ignoring it, or doing something to take your mind off it (like walking, talking to someone or going to sleep)
best of luck.

Diabetes will cause frequent urination and/or excessive thirst, have your blood sugars checked, but if you've been to a doctor, a smart doctor would have already thought of this.