Londoners with B negative blood types are being urged to donate after the NHS warned that supplies are low, putting increased pressure on medical services.
A combination of low numbers of existing B negative donors and recent high demand for B negative blood has left stocks under pressure.
More than 2,000 appointments are available this week, and the NHS is urging B-negative donors to come forward.
Only two percent of the population have B negative blood, making it one of the rarest types.
And patients with the B negative blood type can only receive B negative or O negative blood, meaning that low stocks of B negative can also impact emergency O negative supplies.
Gerry Gogarty, Director of Blood Supply, said: “B negative donors are immensely important to our lifesaving work, but as this blood type is only found in two per cent of the population, it can be a challenge to always collect enough.
“Right now, B negative stocks are at risk of running low. With this blood type, just a slight rise in hospital demand or one or two patients suddenly requiring a high number of units, can put significant extra pressure on supplies.
“We are calling on existing B negative donors to come forward and donate, and more people with this blood type to become regular donors and help secure the lifesaving supply of blood to patients in the months and years ahead.”
Existing B negative donors will be given priority access to appointments and are urged to call 0300 123 23 23 if they are struggling to find availability.
Alternatively, donors can walk in for an appointment at one of the permanent donor centres in West End, Brixton, Edgware, Shepherd’s Bush, Tooting or Twickenham.
Currently fewer than 20,000 people with B negative blood in England donate regularly.
Hospitals across England need more than 5,000 blood donations every day to ensure they have the blood they need to treat patients for a wide variety of reasons, including traumatic injuries or accidents, cancer treatments, sickle cell and childbirth.
As well as B negative, there is also an ongoing need for more donors with O negative and RO blood types.
Donating a unit of blood takes just an hour and each donation can save up to three lives. Men can give blood every three months and women every four months.
Book an appointment at www.blood.co.uk, use the GiveBlood app or call 0300 123 23 23.
