How does one's menstrual cycle effect hemoglobin, hematocrit and so on.?

If women have heavy bleeding or irregular bleeding, they often check for anemia because you can lose enough that you have a drop in iron and everything else ociated with blood. If you aren't losing a lot, it normally doesn't make a difference. However, if you are low to start with-menstrual bleeding can cause it to be just a little lower and for you to feel worse. Donating blood shouldn't make a big difference other than fairly immediate effects, but that is why they check your iron levels before donating and tell you to drink a lot of fluid after donating.