The Australian Red Cross Blood Service have made an urgent appeal for people with O-negative blood to make a donation as supplies drop to critically low levels amid the worst influenza season on record.

Blood banks on the east coast have just one day's supply of O-negative blood, the lowest in over five years, a direct result of roughly 3000 donors weekly cancelling their appointments because they are sick with a cold or the flu.

To replenish supplies, an additional 3000 people with O-negative blood need to make a donation within the next fortnight, by September 15.

"A unpredictably longer cold and flu season has impacted the number of regular donors who are available to give O-negative reserves," according to the Blood Service.