Blood contains iron. Our body needs iron to function well. If you do not have enough of iron, you will contract iron deficiency and it leads to a lot of health problems, especially anemia.
But if you have too much of iron, you will be poisoned. And you will suffer from many diseases, especially liver disease.
It’s ok if you drink or lick a little bit of your blood but don’t have too much.
Never drink blood of anyone else or any animal because you’ll never know whether His/ her/ its blood is pure without AIDS, HIV, hep B, hep C…not to mention that having too much can poison you.
Human blood would be a terrible drink for humans. Not only would it have an excellent chance of spreading disease, it has very little nutrition and contains toxic components.
The disease concern is obvious. Any blood-borne disease (hepatitis C, hepatitis B, HIV, many more) would have the potential for spreading this way.
As for nutrition, blood is mostly liquid. If we look to vampire bats to see how they manage, we see that vampires drink over half their weight at each 30-minute meal . They manage this by rapidly absorbing the nutritive parts of the blood and peeing away the rest . Humans aren’t able to do either of these — the rapid absorption and the rapid urination are both specific adaptations — so humans would have a hard time getting much nutrition from blood.
Then there’s the toxicity issue. Blood is very rich in iron, obviously, and iron is very toxic. (Iron poisoning is one of the more common toxicities in children.) Again, vampire bats have specific adaptations to deal with this (“The common vampire bat maintains iron balance by severely limiting the percentage of iron absorbed from its very high iron diet” ). Humans trying to get enough nutrition from blood would poison themselves with iron.
If you drink human blood in a daily basis, sooner or later you’ll go to jail. Animal blood? the idea is creepy, but there are Kenyan tribes that do this and give evidence of unusual stamina. It won’t necessarily be harmful to you. Animal pathogesn are less of a problem than human pathogens. Human blood is just something you should never consume.