The Red Cross urgently needs almost 6000 people to give blood over the next two weeks, with cold and flu cases hitting blood stocks hard.

An early start to the cold and flu season has taken a heavy toll on blood donations, with the Red Cross issuing an urgent appeal for help from health Aussies.

The Red Cross Blood Service needs 5,900 additional people to give blood over the next fortnight, with up to 1,400 donors cancelling their appointments each day due to illness.

The Red Cross says it urgently needs help, particularly donors with O and A type blood.

"We haven't seen cancellations this high since March 2017, and as the number of people suffering cold and flu symptoms increases, it limits the number of regular donors who are able to give," blood service spokeswoman Helen Walsh says.

"We need people who are fully recovered from colds or the flu, and those who have avoided it, to take the place of those who are unable to answer our call."

People can still donate blood if they've had the flu shot.

Donors who have had colds or the flu can give blood again seven days after they have recovered.