I was at a meeting a couple weeks ago out of town, and I was called in to inspect the sheets in a room for others as they believed they were dirty, and being the innkeeper that I am stated clearly they were cleaned, set-in, blood stains, to which they all said "Ewwwww" and I just kind of shrugged and walked out. My expertise was needed and the stains were clean stains. Not what they wanted to hear, but better than the alternative, I told them.
(oh what they don't want to really know about hotel rooms, and I won't be sharing with them anytime soon, I did say "remember at a b&B the innkeeper is 100% on top of inspecting the rooms and many times cleaning them him/herself.)
I've used meat tenderizer, peroxide, cold water, hot water, soaking, etc and most of those sheets are now mine. What is really needed and not supplied by a front loader is water and lots of it. The only way to get blood stains out is scrubbing in the sink. Not trying to let the washing machine do it for you.
I've had a lot of success with oxy and detergent and I let it soak for a while, then wash. I wash everything in my front-loader. After it is washed, we pull it in four hands to see if the stain is gone. If it is, fine, it can go in the dryer. If not, it gets another treatment with oxy and a different stain remover. Until the stain is 100% gone and it can go in the dryer.
Sorry ladies, but I can tell you that the first time I was traumatized!
Ideally, you would want to tackle the stain with water right away. The fresher the blood is, the more effective it is to clean it off. And then, apply some soap on it. Give it a good rub all over the stain. And if you're dealing with light-color fabric, hydrogen peroxide (which will act as bleach) will be a good option. In worse cases when the blood has dried, you'll need to put more work into it. First, apply some pre-treatment products which could be found anywhere on the market. Then use enzyme-based laundry detergent to wash off the stain. This could be applied to bed sheets, shoes, and any kinds of fabric or leather materials.
I've only tried it with white, but Hydrogen Peroxide almost always gets it out. Sooner you start treating it, the faster it comes out - almost instantly. Before washing, just literally spot treat it; pour it undiluted over the stain; you will see it bubble up; give it a few minutes. If the stain has been dry a while, it may take several treatments, some brushing. I have come to the conclusion that all blood is not red. I think that some folks may have so much medication (or whatever) in their blood that it affects how easily it comes out. Also, some folks drool and it's mixed with blood - so it looks like blood, but you are not sure. Hydrogen Peroxide works great.