I am very upfront so I always waited until the end of the second date. If there was going to be a third date then I felt they should know so they could decide if they wanted to keep seeing me.

For what it's worth I never had anyone freak out when I told them or say they couldn't date me because I was bipolar. I did have several ask if I took medication, how often I got manic, general explanation of what bipolar is etc.. but no freak outs or being dumped because of it so that was good

Good luck to you