Snake blood and snake venom are two completely different things. A snake produces venom inside its venom glands. The snake injects this venom through its fangs when it bites. This venom becomes highly dangerous when it enters human blood or tissues. But drinking snake blood does not always cause poisoning.
Snake blood does not naturally contain venom. Even if some venom mixes with the blood, the impact depends on the venom amount, the entry method, and the person’s health. A person might not fall sick immediately after drinking it, but this practice is never safe.