Drug testing is one-way employers can maintain a secure and efficient workplace by removing substance abuse to cut down on accidents and increase efficiency. Pre-employment screening allows candidates to be screened before being hired, random testing helps deter drug use among employees and post-accident tests evaluate if drugs could have contributed to workplace incidents. In order to be effective, though, the business should maintain a comprehensive written document that includes every procedure and consequence, as well as communicate with employees about rights and expectations. Policies should address prescription medicines and medical marijuana.