Red Cross Lifeblood is appealing for an extra 8500 people with the valuable O and A blood groups to donate in the next fortnight because of an increase in cancellations.

A rise in flu cases at this time of year, combined with COVID-19 cases, means about 2000 donors a week are cancelling and rescheduling appointments.

Lifeblood's executive director of donor experience, Cath Stone, said more than 80 per cent of the population has an O or A blood type, which are most needed by patients.

"O negative, the universal blood type, is found in fewer than seven per cent of the population, making it one of the rarer blood types,'' Ms Stone said.

"However, its versatility means it makes up 16 per cent of the blood ordered by hospitals.

"It's often stocked in ambulances and rescue helicopters to be used to treat trauma patients who can require huge quantities of blood in a short amount of time."

To make an appointment, contact Lifeblood on 13 14 95.

Australian Associated Press