There are a lot of DIY cleaning hacks out there on YouTube. Please be cautious before trying an unfounded DIY tip for removing blood from carpet. As a professional carpet cleaner in Tampa FL I have been i n a lot of homes where the home owner has already damaged their carpet by using carpet cleaning advice they found online. There are several ways to get blood out of carpet but your best bet is to use a store bought carpet cleaning solution, but in a pinch there are some things that you can use to minimize the stain.
My favorite universal carpet cleaning agent is carbonated water. If you have a soda stream you have one the bet carpet cleaners out there. I have used carbonated water in a pinch on several things that have found there way into the carpet. This video shows a good remedy for removing blood from carpet. Just replace the water with carbonated water and you will amp up the cleaning power 10 fold.
If that doesn't remove all the blood in the carpet you can try it again with about a half teaspoon of Hydrogen Peroxide 3% into the water and clean it again. Make sure when you're all done cleaning it that you place a dry towel over the cleaned spot and stand on it for about 30 seconds. That will push all the moisture out of the carpet pad underneath and dry out the carpet faster. If this carpet cleaning recipe doesn't work for you then you might want to call a professional carpet cleaner.