A method used in clinical trials so the participant doesn’t know which medicine they are taking and neither does the health professional monitoring and treating them. That is, they are both ‘blind’ to the treatment.

Blinding aims to get rid of any unintended influence, or bias, caused by the participants’ and health professionals’ expectations of the medicine, which might affect the way they respond to treatment or assess any changes in the person’s health. Blinded trial results are considered more reliable.