11:00 PM - 1:00 AM
This is the time your gall bladder is most active. The bile stored in your gall bladder works to break down everything you ate before you slept and digest it properly.
If you're waking up between 11:00 p.m to 1:00 a.m, it may be because your body is having trouble absorbing your last meal. Try eating earlier or ask your doctor if you suffer from a food intolerance.
There was a time I was always waking up at this time. I visited my doctor, and after several tests, she discovered that I have a dairy intolerance.