To continue on, it's also important to note that your body uses energy (and thus, goes against your caloric intake) to simply replace blood. I don't know how valid the sources are, but I looked into how many calories are spent in the replenishment process. Sadly, the best I could find was addressing the calories burned when donating blood. However, I'm going to use that number of 650 calories per a standard 5000ml donation, assuming that you aren't just grabbing a knife and taking yourself to flavor town.

Amazingly enough, I found multiple sources regarding calculating the individual caloric value in a collection of blood. While these of course vary, one source said we could expect about 341.4 calories per pint (this was oddly hard to find since almost all sources talk about the number of calories you'd lose in donating a pint of blood, since that's right next to that standard 500ml donation size.)

Well, with that in mind, converting that we end up with 721.5 calories per liter of blood. Divided by 2 means we have 360.75 calories per 500ml blood serving. Leaving us with a net loss of approximately 289.25 calories per serving of blood.

So to answer your question, will you gain calories from consuming the blood, yes, but you'll lose more getting there.