England's blood donor service has warned blood stocks are still in short supply as it launches a fresh appeal for donors. Supplies of blood have improved since an "amber alert" in July but there is still a risk that the care of hospital patients could be impacted, officials said. The number of people booking appointments to donate is dropping off over the coming months, said the service.

Young donors are urged to come forward, especially those with O negative blood type, and more donors of black heritage are also being sought to help treat patients with sickle cell disease. In July, for only the second time in its history , the NHS warned hospitals that stocks of O-type blood - which can be given to the vast majority of patients - were running low enough to have an impact on patient treatment. This is known as an amber alert.

The NHS said it was due to a "perfect storm" of unfilled appointments at donor centres and increased demand following a cyber-attack, which affected services in London. At that time, stocks of O negative stood at just 1.6 days, and 4.

3 days for all types of blood. O negative blood is universal and can be given to anyone. It is used in emergencies or when a patient’s blood type is unknown.

O positive blood is the most common type and about 35% of donors have it. It can be given to anybody with a positive blood type and all men and women past childbearing age. Stocks of O negative blood are now at 7.

8 days and overall stocks of all blood types have risen.