Getting a blood stain out of clothing is not an easy task, but I know a way that works every time if you catch it before the stain sets.
Run the blood stain under cold, cold water.
Scrub it with Safeguard bar soap.
Rub the clothing together vigorously.
Repeat if necessary.
I don't know if another brand of soap can be used; I just know that that's what I've used and works. This is a fail-proof method ~ great for cleaning up after your kids' scrapped knees or your unmentionables during [ahem] that time of the month.