im sorry to be all gory and for making people grossed out! but this is normal. Anyway when spells/hex's/curses and whatever when they are use blood where you have too either prick your thumb/finger with a needle or cut your hand with a knife.
instead of doing that way would you be able to use your Menarche? because when it comes to spells using blood I can't really see myself doing that.
giving blood for a spell