More than 10,000 blood donors are urgently needed to prevent a nation-wide shortage of plasma and blood.

A nationwide shortage of blood and plasma stocks could be only weeks away if more than 10,000 additional donors do not sign up to give blood.

Each week, 31,000 donations are needed to help Australians through trauma, major surgery, cancer treatment, pregnancy and a host of other situations.

But, over the past three months, Red Cross' Lifeblood service has seen a drastic increase in no-shows and cancellations.

Looking ahead, the number of appointments in the next few weeks has also dropped.

"To meet the needs of Australian patients, we really need 10,383 additional people to donate over the next two weeks," Lifeblood chief executive Shelly Park said.

She is concerned confusion about lockdown measures may be keeping people away.

"Donating blood and plasma is classed as essential care giving and we have worked with all state and territory governments to make sure donors can keep their appointments, even in lockdown."

Ms Park says donation centres are COVID-safe, with strict social distancing, temperature checks and regular, thorough cleaning.

People who want to become blood donors can visit the Lifeblood website or call 13 14 95 to set up an appointment.