In 2022, nearly a quarter of a million people signed up to donate blood, but only about 200,000 have done so.
Only about 91,000 of the 325,000 people who were registered—according to exclusive data provided to BBC 5Live by NHS Blood and Transplant—have scheduled an appointment.
Due to low blood supplies in 2022, the NHS claimed that current donors would be given priority, resulting in fewer appointments for first-time donors.
At the biggest blood processing facility in the UK, which is close to Bristol, I've been explaining why it's crucial for people to make appointments right away.
Phil Brown, a 35-year employee of the NHS Blood and Transplant Centre, required "multiple" blood transfusions to treat his leukemia.
As part of his treatment, he said, "I received numerous red cell and platelet transfusions. Twenty years ago, I had leukaemia, and I believe leukaemia and bone marrow cancer.".
Making sure all the products are processed correctly and are safe and therapeutically effective is one of the main reasons I [work at the center] is motivated. It is very significant. ".
Mark Chambers, assistant director at the Filton facility, said: "Trying to get more donors is challenging in this situation.
"In October, we faced a problem when our blood supplies fell to just two days' worth, prompting an amber alert.
"We're now approaching six and a half days, but we are aware that many donors have registered to try and enter the building. ".
He claimed that O negative and RO are currently the two types that are most required.
Because O negative is a blood type that can be given to any patient, he explained, we need it.
"We need donors who are RO for sickle cell, and this is typically found in donors with black heritage. ".
The NHS stated that the service would have a difficult year in 2022 due to low blood supplies.
Existing donors are given priority during these times because their blood type is known and they are more likely to complete a successful donation, the statement read.
According to the statement, blood supplies have since "stabilized," and more slots are now open for new donors. Those who have already registered are urged to book right away.
"We always need new people to join our amazing community of life-saving blood donors and help meet the needs of patients right now and in the future," said David Rose, director of donor experience at NHS Blood and Transplant. "Please make 2023 the year you save lives if you are one of the 235,000 people who registered last year but have not yet gone to your appointment or are considering signing up to donate.