I discovered by accident that Vitamin B-12 makes me sleep really well when I take it at night. However, it makes me very groggy during the day. Eventually the dose I take will not make me sleep as well at night, so I increase the dose, but again it makes me very groggy during the day. I've tried smaller dose increases, but in order sleep well at night, I have to take a dose that makes me sleepy during the day. I wonder one, why this is happening as B-12 generally gives people more energy. And two, is the grogginess part of my body trying to get more sleep or something more sinister? So I thought I'd pick the brains of the good folks here. Thanks so much!