Blood donors are being urged to help boost stocks as severe weather grips South Yorkshire.
Existing donors of all blood groups are urged to give blood if it is safe to travel to donation sites.
NHS Blood and Transplant said the need for blood is constant but because of recent freezing weather and snow, many people have not been able to donate.
The bad weather has also led to some sessions being cancelled.
Hospitals need 6,000 units of blood every day across England to treat patients in need.
A+ and A- platelet donors who have booked appointments are also being urged to try to make their sessions.
Platelets only have a five day shelf life, so stocks need to be replenished daily.
Donors are being urged to turn up to give blood without an appointment at fixed site donor centres, of which there are 23 in the country including Sheffield.
Those who are not near a fixed site donor centre are being asked to book an appointment.
Mike Stredder, NHS Blood and Transplant's Director of Blood Donation, said: "The recent poor weather caused the cancellation of sessions in snow hit areas and meant we collected less blood than we needed, particularly Group A, Group O and B positive donations
"Seriously ill patients need blood every day and they rely on the generosity of people making time to donate.
"So, we are appealing for existing donors to check the weather before they travel but, if it’s safe for them to get out, we need them to come along to a session and donate if they are able. If not then please book an appointment for the near future to ensure we keep up the momentum and collect enough blood to meet the needs of patients. Please take action now and walk in and donate – you will save lives."
Call the Donor Line on 0300 123 23 23 or visiting www.blood.co.uk to make an appointment.
For details of fixed site donor centres visit www.blood.co.uk/the-donation-process/about-our-donation-venues.