Blinding is a methodological tool in clinical studies where information about which treatment a participant receives is concealed from one or more parties. A double-blind approach is the gold standard in phase II and III clinical trials with the goal to reduce bias. It usually relates to blinding of both the participant and the investigator. Not all randomized clinical studies are double blinded, they can be single blinded or open label as well, depending on the drug or medical device that is tested. Blinding is not done when it is impractical or unethical.
