Is blood toxic to drink?

In very small amounts (say, a few teaspoons), and if the blood is free from pathogens (such as the many blood-borne diseases), blood might not harm you. Beyond that, watch out.

The strange fact is blood, when drank, is toxic. When confined to places where blood is supposed to be — such as the heart, vessels, and so on — it is essential for life. But when ingested it's a very different story. Of course, all toxins have doses, and just as a tiny bit of poison won't necessarily harm you, the more you eat or drink, the greater the danger.

Because blood is so rich in iron — and because the body has difficulty excreting excess iron — any animal that consumes blood regularly runs a risk of iron overdose. While iron is necessary for all animals (and indeed most life), in high doses it can be toxic. This condition, called haemochromatosis, can cause a wide variety of diseases and problems, including liver damage, the buildup of fluid in the lungs, dehydration, low blood pressure, and nervous disorders.