The rule change will allow those who lived in the United Kingdom (UK) between 1980-1996 the chance to donate blood - an option that previously hadn't been on offer as a precautionary measure to 'mad cow disease'.

Australian Red Cross Lifeblood spokesperson Jemma Falkenmire said about 750,000 people around Australia had been impacted by this rule, which prevented those who had spent six or more months in the UK during the 16 years to donate blood.

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"We are expecting that hopefully 3 per cent of those people will donate," Ms Falkenmire said.

It is hoped the change will help fill more appointments with Tamworth's Lifeblood Donor Centre still struggling with no shows and cancellations due to COVID.

Ms Falkenmire said just this week there is more than 70 appointments waiting to be filled.

"We do have a lot of empty couches in our donor centre in Tamworth," she said.

"We've extended our opening hours and we're open on some weekends.

The eligibility change was 12 months in the making and was approved by the Therapeutic Goods Administration (TGA) last week.

Ms Falkenmire said Lifeblood was required to make a scientific case that there would be no risk to the Australian blood supply.

While there is not yet a date set for when the new spate of donors will be eligible to roll up their sleeves, Ms Falkenmire said the change had come at the perfect time.

"We have seen lots of people for various reasons unable to donate during the pandemic," she said.

"But recently demand for blood has been quite high from the hospitals, there's been returns to elective surgery, increases in accidents and emergencies and just regular patients like cancer patients needing blood."

Those affected by the change are encouraged to contact Australian Red Cross Lifeblood on 13 14 95 to find out when they can donate.