Pharmacogenetics studies how a person's genetic makeup affects their response to drugs. It aims to develop personalized drug regimens to improve drug efficacy and safety. Every year in the US, adverse drug reactions cause 2 million people to experience side effects and over 100,000 die from reactions. Current drugs are only effective in 60% of the population. Pharmacogenetics uses genetic tests to determine a patient's risk of side effects or likelihood of response to a drug to help guide safer and more effective treatment decisions.