I can usually tell when I'm hypo, but not always. Sometimes I'll feel perfectly fine, but I'll see it in the things I'm doing. I'll be like nope, I'm not manic, but I just cleaned the garage for the third time and tore all the books off the bookshelf and put them back in order of color. Then tore them off again at 3am and reorganized them by size. That sort of thing. Other times I can definitely feel it.