Red Cross Lifeblood is in dire need of donors, with A+ and O+ blood plummeting to a two-day supply.
About 71 per cent of Australians have A+ or O+ blood.
The organisation says they need 16,000 more blood and plasma donors over the next fortnight to meet demand.
During the pandemic Australians have been hesitant to donate blood. According to Lifeblood, 1200 donors cancel or are no-shows to their appointments each day.
Lifeblood executive director Cath Stone said 31,000 donations were needed weekly across Australia.
Donated blood helps patients in situations from trauma to pregnancy to cancer treatment and more.
Ms Stone said blood donations were essential to the public health of Australia, and donation facilities were clean and COVID-safe.
"Only healthy people are eligible to give blood and we have introduced even more stringent wellness checks prior to appointments, including temperature checking," Ms Stone said.
"As restrictions return in SA, and are eased in other parts of the country, it's essential that blood and plasma donations continue."
"We saw the absolute best of the community throughout the pandemic with donors continuing to come in, however, this recent trend of decreasing appointments and increasing cancellations is concerning."
"We want to thank everyone who has continued to step up and donate during COVID-19. However, the need for blood and blood products never stops so we urge those who can to make blood or plasma donation part of their 'new normal'."
Ms Stone and Lifeblood have encouraged first time donors to step up and donate.
"Even if you don't know what blood type you have, we still need you - we need all blood types every day."
- To book a blood or plasma donation visit lifeblood.com.au, call 13 14 95 or download the Donate Blood app.