The NHS has made an urgent appeal for more blood donors after a national alert over supplies dropping to an “unprecedentedly low” level. O-negative blood – known as the universal blood type – is safe for all patients requiring blood transfusions. Making up about 16% of all hospital orders, it is used in emergencies or when a patient’s blood type is unknown. About 40% of the UK population have O-positive blood, while 8% are O-negative. NHS officials have issued an amber alert, asking hospitals across England to restrict the use of O-type blood to essential cases. According to the latest figures from NHS Blood and Transplant (NHSBT), national stocks of O-negative blood are at just 1.6 days, compared with the six-day target. By comparison, there are 11.32 days’ supply of AB-positive blood. The shortage has been attributed to the cyber-attack on the NHS. Since the attack in early June, hospitals such as King’s and Guy’s and St Thomas’ in London have had to use O-type blood, as blood checks could not be carried out as quickly as usual, leading to a 94% increase in demand compared with the same period last year. Dr Jo Farrar, the chief executive of NHS Blood and Transplant, said: “We urgently need more O-group donors to come forward and help boost stocks to treat patients needing treatment. “Last month we saw an incredible response from donors who answered our call and filled up our centres, helping us meet the increased demands for blood throughout June. However, seven weeks on, the need for O-negative blood, in particular, remains critical.” The NHS has said it needs to collect 1.45m units of blood and recruit up to 200,000 new blood donors each year to replace those who stop donating and to ensure the right mix of blood groups for the needs of future patients. To book an appointment to give blood, call 0300 123 23 23 or visit blood.co.uk.