Snow and icy conditions are putting pressure on the NHS, resulting in staff shortages, dwindling blood supplies and record number of calls to ambulance services.
The Royal College of Nursing said that winter planning had improved in recent years but this would be a testing time for the NHS.
Ambulance services are reporting a high number of calls, and have urged people to call only for life-threatening emergencies and to avoid venturing out in their cars.
In addition, emergency departments are reporting an increased number of cases related to chest infections, pneumonia, snow-related injuries and flu-like illnesses.
Health Secretary Andrew Lansley said the recent bad weather has made it difficult for staff and donors to attend sessions and give blood, and has encouraged people to continue donating so that the NHS can continue to carry out procedures.