The term "high voltage" usually refers to electrical energy that is high enough to cause harm to living organisms. Equipment and conductors with high voltage require special safety requirements and procedures. In some industries, high voltage represents a voltage above a specific threshold (see below). High voltage is used in power distribution, cathode ray tube, X-ray and particle beam generation, demonstration of arc, ignition, photomultiplier tube, high power amplifier vacuum tube and other industrial and scientific applications.

If a voltage greater than 50 V applied to unbroken human skin produces an electrical current in the body tissue that just passes through the chest area, it can cause heart fibrillation.

The voltage at which there is a risk of electric shock depends on the conductivity of dry human skin. The insulation of dry skin up to 50 volts protects living human tissues from damage. If the same skin becomes wet, has a wound or applies voltage to the electrode penetrating the skin, even a voltage source lower than 40 V can be fatal.

Accidental contact with high pressure that provides enough energy can cause serious personal injury or even death. This happens when the body provides a path for electricity, leading to tissue damage and heart failure. Other injuries may include arc burns due to accidental contact. These burns can be particularly dangerous if the victim's respiratory tract is affected. The physical strength of a person who falls from a high altitude or is thrown a long distance may also cause injury.

Low energy exposure to high pressure can be harmless, such as sparks when touching the door handle after crossing the carpet floor in a dry climate. The voltage can be in the kilovolt range, but the current (charge transfer rate) is very low.

Safety equipment used by electrical workers includes insulated rubber gloves and mats. These protect the user from electric shock. Safety equipment is tested regularly to ensure that users are still protected. Test regulations vary by country. Testing companies can test at voltages up to 300000 volts and provide services from glove testing to elevated work platform (or EWP) testing.