If you're not man enough to procure some real blood, just use the fake stuff.
Seriously, just google 'fake blood' - there are tons of recipes...
Halloween is not far away now, so you should even see it selling in Walmart or whatever in the next month or two...
If you're shooting B&W, it's even easier because it doesn't have to actually look like blood. I've heard of chocolate syrup being used a lot for fake B&W blood...
I'm sure not all blood recipes are created equally, so it may take a little trial & error to find the right one - but it's not hard, and there are literally thousands of recipes out there.
Motor Oil
Red Food Dye
Coffee Grinds
Simple syrup or corn syrup
As far as amounts, the base is the syrup. The motor oil is for darkness and consistency, the coffee grinds to make it look congealed, and the red food dye for color. Pretty simple set up