There is only a day's worth of O-negative blood in reserve at the Australian Red Cross due to this winter's cold and flu season.

The service's Jennifer Campbell Case said sick donors were cancelling their appointments, reducing the stocks of the sought-after blood.

"Nationally about 1,000 appointments are normally cancelled each day but over this cold and flu season it has spiked to 3,000," she said.

"That's unprecedented for us."

O-negative blood is the universal blood type given to patients in emergency situations or when their blood type is unknown.

Only 9 per cent of people have O-negative blood, and over 3,000 people are needed to donate in the next fortnight to replenish supply.

It is the worst flu season in the last five years in Queensland, with about 20,000 cases this year.