Bad weather, ill health and busy schedules in the run up to Christmas result in a drop in donations most years.
But hospitals across the UK will need around 6,000 units of blood a day for patients.
Amanda Eccles, Senior Marketing Coordinator at NHS Blood and Transplant, said: “This is the time of year when we need our amazing donors in South Yorkshire more than ever.
“If you can make and keep an appointment this December you will be doing an incredibly important thing – helping us to save and improve lives at a time when patients need every donor.
Anyone interwsted should call 0300 123 23 23 or visit www.blood.co.uk to book an appointment.