Snake venom affects the human body in a number of ways, depending on the snake, the type of venom, and how much venom is released. Different snakes produce different types of venom, and even within a snake species, the components of venom appear to vary, depending on geographic location. This is why it is important to be able to identify the snake species involved when one is bitten, so that the appropriate anti-venom can be administered.

There are basically three different kinds of snake venom. Hemotoxic venom is designed to assault the cardiovascular system. Cytotoxic venom targets specific sites or muscle groups, while neurotoxic venom goes after the brain and nervous system. Some snakes combine venom types for a more effective bite, while others only carry one specific form of venom. All venoms contain a complex cocktail of proteins and enzymes.

When someone is bitten by a snake with hemotoxic venom, the venom typically acts to lower blood pressure and encourage blood clotting. The venom may also attack the heart muscle with the goal of causing death. Cytotoxic venom is designed to cause tissue death, which is why some people have to receive amputations after being bitten, because the venom has eaten away the localized tissue. Many cytotoxic venoms can also spread through the body, increasing muscle permeability so that the venom can penetrate quickly.

A neurotoxic venom works to disrupt the function of the brain and nervous system. Classically, such snake venom causes paralysis or lack of muscle control, but it can also disrupt the individual signals sent between neurons and muscles. Such venoms can also attack the body's supply of ATP, a nucleotide which is critical in energy transfer between cells.

Researchers once believed that many snake venoms contained digestive enzymes to make it easier to process prey. However, this does not appear to be the case; snakes with digestive enzymes in their venom don't digest prey any more quickly. More probably, such snake venom contributes to tissue death by literally eating the tissue away, accomplishing the snake's goal of incapacitating a victim long enough to start eating.

Some animals have natural immunities to snake venom, and immunities can also be induced through careful applications of processed venom; this technique is used to make the anti-venom used in snakebite treatments. Because there are around 300 venomous snakes in the world, many nations have anti-venom exchange programs, which ensure that hospitals and treatment centers can get needed anti-venom from other facilities in an emergency.