Forecasters are warning of the dangers to vulnerable patients as cold weather bites across the UK.
The Met Office says freezing temperatures could "increase the health risks... and disrupt the delivery of services".
The cold weather alert in place until 12:00 GMT on Wednesday says northern England and the Midlands are at risk.
Temperatures plunged below freezing in parts of the UK earlier, amid warnings of treacherous conditions on icy roads.
The lowest recorded temperature was almost -5C (23F) in Perthshire overnight with "widespread" frost hitting large areas of the country, the BBC Weather centre said.
Daytime highs around the UK ranged from 1C (34F) in Lincoln to 5C (41F) in south Wales and the south coast of England.
But the forecasters predict the temperature could drop below freezing even in southern cities on Sunday night and could fall as low as -10C (14F) in rural areas.
The Met Office cold weather alert warns of there is a 90% chance of severe conditions including icy conditions and snow.
The amber - level three - alert for the north of England and Midlands is one below a national emergency and indicates social and healthcare services should target "high-risk" groups, such as the very young or old, or those with chronic diseases.
A yellow - level two - alert is in place in the rest of England indicating social and healthcare services should be working to ensure they are ready for a period of cold weather.
The BBC's Peter Gibbs forecasts colder temperatures
Wintry showers hit Northern Ireland, Wales and eastern England on Saturday, with the town of Leek in Staffordshire recording the day's heaviest snowfall of 12cm (4.7in).
A section of the M62 near Huyton was closed after an accident. In Derbyshire, part of the A6024 near High Peak was closed and in south Yorkshire the A631 near Beckingham was closed - both because of ice.
Snow covered hills around Macclesfield on Sunday 
A crashed car stands abandoned on a snow covered verge near Sheffield on Saturday BBC Weather's Philip Avery said some of the lowest recorded temperatures overnight had been in areas where snow had already fallen.
He said temperatures had fallen to below freezing in parts of northern Scotland, while in much of England, Wales and Northern Ireland it was either close to or below zero.
The AA tweeted a picture of gridlock in Sheffield on Saturday - Balance your speed - too fast and you risk losing control, but if you go too slow you risk losing momentum
- Start gently in second gear, avoiding high revs. Stay in a higher gear for better control
- Only use the brake if you cannot steer out of trouble
- Increase the distance at which you follow other vehicles
- Plan your journey around busier roads, which are more likely to have been gritted
- On a downhill slope, get your speed low before you start the descent, and do not let it build up
- In falling snow, use dipped headlights or fog lights, but switch off if conditions improve
- Read more about how to prepare your car
Has your journey been affected by snow and ice? Have you changed your plans because of the weather? Email your comment to haveyoursay@bbc.co.uk
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Cold weather warnings follow freeze
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