hydrogen peroxide (the stuff in the brown bottle) sometimes works

Easy ... do what lab techs do: soak the cloth in cold water to remove most of it, then pour hydrogen peroxide onto it to get the rest out.

If there is a trace of yellowish color left, a bit of barkeeper's friend sprinkled on the wet stain should get rid of it.

Was this a MURDER SCENE?!? Not sure how it will work on blood but have had success removing that food schmutz that ended up of thumb/tips of off-white terry oven mitts. Dawn makes something called "power dissolver"... or something like that?? Original use is to spray that casserole that you put in dishwasher, knowing full well... it's NOT coming out spotless. It comes in a pump/spray, sprays one kinda foamy, has that slippery feeling like oven cleaner but NOT those nasty fumes. Got rid of at least 90% of stuff that hadn't budged thru regular washing.

I recently cut my finger and it dripped on my blouse. I just put it in a sink of cold water and left it all night.....didn't even use any soap and the blood was gone. It was fresh blood, don't know if old blood will come out.

Enzymes in saliva from owner of the blood will work. Spit on the stain and rub in, let set for a few minutes. Repeat as necessary.

Quilters do this when they prick their finger and get blood on the quilt.

soak in water with salt

Cold water and Dawn dish detergent.