Urgent appeal for blood donors as stocks run low
20 December 2010 Last updated at 16:17 GMT
The NHS is appealing for people to donate blood because of low stocks caused by the bad weather.
The NHS Blood and Transplant Service said stocks of O negative have fallen below "preferred levels".
O negative is an a key blood type because it can be given safely to patients in other blood groups.
The BBC's medical correspondent Fergus Walsh, who has O negative blood visited a blood donation session in London.