O positive is the most common blood type, and apperently O-neg folk can handle O-pos once, so O-pos is generally the most commonly used for a crisis. Source: MD partner just checked openevidence
Edit: O-pos is 40% of the population, O-neg is 6%, so they prefer to use O-pos. The real risk is just not having enough blood.
Reading more, some 2019 source says only 1 in 2 million O-neg would die from O-pos blood. So really, almost everyone can use O-pos
O positive is the most common blood type, and apperently O-neg folk can handle O-pos once, so O-pos is generally the most commonly used for a crisis. Source: MD partner just checked openevidence Edit: O-pos is 40% of the population, O-neg is 6%, so they prefer to use O-pos. The real risk is just not having enough blood. Reading more, some 2019 source says only 1 in 2 million O-neg would die from O-pos blood. So really, almost everyone can use O-pos