But if you try hard enough, you can find a positive in just about all of them.

And there would be few more positive sights for the staff across Australia's blood banks at the moment than new O-negative donors, given the nation's supply of live-saving blood is under critical pressure.

Blood donations are at record low levels as illnesses force donors to cancel appointments.

About 30,000 donor appointments per week are being cancelled, postponed or simply not attended, leaving centres with less than a day's worth of O-negative blood in reserve.

O-negative blood can be given to anyone in need of a transfusion but fewer than one in 14 Australians have it, making about 7 per cent of the population particularly valuable to Red Cross.

There are seven other main blood types, with some more rare or versatile than others.

But Lifeblood, the Red Cross branch that manages the nation's life-saving blood products, does not discriminate.

As it says on its website, "we love them all equally".

That has perhaps never been more true than it is this winter as the so-called "triple threat" of COVID-19, the flu and other respiratory illnesses keeps donors away from blood banks.

And so it is time for us in the Wimmera who are able to donate to roll up their sleeves and start saving lives.

Someone you know is bound to need blood one day because one in three Australians do at some point.

What that means is a donation is needed in this country every 18 seconds.

If you are not motivated simply by knowing blood donation is likely to have an impact on your life or that of someone you love, Kate Waterford's story illustrates the importance of the issue.

She has been giving blood for more than 10 years, and has this weekend urged new or lapsed donors to help make up the shortfalls at centres that have been almost empty in recent days.

Ms Waterford knows the power of blood donation not only because she has given her own, but also because transfusions have saved her life on three occasions.

She will never know the names of the people who kept her alive, nor will those she has saved know hers.

That sort of selflessness is why those who give the gift of life are, as Ms Waterford puts it, "absolute heroes".

For information about donating blood or to book an appointment, visit www.lifeblood.com.au.