Use of face mask by blood donors during the COVID-19 pandemic: Impact on donor hemoglobin concentration: A bane or a boon.

Background: COVID-19 virus has caused the world's deadliest pandemic. Early April 2020, the Delhi Government made it compulsory for people to wear face masks while going outdoors to curb disease spread. Prolonged use of surgical masks during the pandemic has been reported to cause many adverse effects.