Hospitals across the country cancelled outpatient appointments and non-urgent surgery as they coped with staff absences and increased emergency admissions brought on by heavy snow.
London and the South were particularly badly affected on Monday, with many operating urgent services only.
There were high rates of absence and NHS London urged staff who could not reach their workplace to offer help at other nearby hospitals.
A spokesman for NHS London said most trusts were affected, with those in south east London suffering particularly badly.
Several central London trusts provided hotel accommodation for staff who volunteered to work late on Monday night, as did the strategic health authority itself.
At one stage, Queen Mary's Hospital in Sidcup was operating with one consultant and one junior doctor, he said.
Several ambulance services prioritised life-threatening calls and issued urged the public to use alternatives.
London Ambulance Service trust got about 50 per cent more calls than usual and was operating with about one third its normal staff levels.
West Midlands Ambulance Service trust took 10 per cent more calls than usual.