Bladder Training

Bladder Training

I've heard that I can train my bladder to go a longer time period before I have to urinate. I usually have to go to the bathroom every 30 minutes. I'm always worried that when I'm out shopping, I won't be able to make it to a toilet in time. It sounds to good to be true that I can train my bladder to hold urine up to three or four hours. Is this wishful thinking? Has anyone tried bladder training? Can you offer advice on how it's done and how it's helped you?