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.

The high rate of flu and other illnesses this winter has greatly impacted the number of regular donors who are able to give, said Blood Service spokesperson Shaun Inguanzo.

NSW Health has recorded almost 60,000 flu cases this year which is an all-time high and almost twice as many as the 35,538 cases diagnosed in 2016.

"Unfortunately, this season has lasted longer than in previous years, so we need other O-negative donors to take the place of those who have been unable to give," Mr Inguanzo said.

"With one in three of us needing donated blood in our lifetime, the life you save could be that of a friend or family member," he said.

O-negative is the universal type, which can be given to patients regardless of their blood type in emergency situations.

Between 8 and 9 per cent of the blood donor population is O-negative, but the blood type accounts for 15 per cent of all hospital demand.

"Most of our O-negative donors know they're special and do come forward to donate when we came an urgent appeal," said Blood Service spokesperson Jemma Falkenmire.

"But many people in the community don't know their blood type, which can be a real challenge for us," Ms Falkenmire said.

Donors who are affected by cold and flu symptoms are able to give blood at least seven days after making a full recovery.