The winter deep freeze poses a "lethal" risk for people who are suffering loneliness, England's top nurse has said.
Professor Jane Cummings, Chief Nursing Officer for England, said lives could be saved by people checking in on vulnerable people, including elderly relatives.
NHS England warned that the combination of isolation and cold weather had a "real impact" on already stretched health services.
The warning follows the coldest night in the UK so far this year, when temperatures plunged to minus 13C on Tuesday night.
Prof Cummings (pictured) said: "Loneliness has a devastating and life-threatening impact on people of all ages.
"For vulnerable groups, social isolation combined with the health dangers of colder weather, is a lethal combination.
"NHS staff see first-hand the consequences of loneliness, from dealing with life-threatening and serious illness to offering a lifeline to those simply wanting a see a friendly face.
"We can all take steps to alleviate loneliness by looking out for family, friends and neighbours.
"These simple acts of companionship could be life-saving."
The health service said evidence showed feeling isolated increased the risk of premature death by around a third, with heart attacks increasing after a cold snap and accounting for 40% of excess winter deaths.
Research for the NHS Stay Well this Winter campaign also found 56% of people aged between 18 to 74 would like to visit elderly relatives, friends and neighbours more often and 42% saying they plan to make it a New Year's resolution.
And two in five 70 to 80-year-olds surveyed said it helped to have someone help them with everyday tasks, with the weekly shop, picking up medicines and getting to the doctor.
Seema Kennedy MP and Rachel Reeves MP, who head the Jo Cox Loneliness Commission set up to continue the work of the murdered Labour MP, said: "The evidence of the impact of loneliness on people's health and well-being is now overwhelming and we are delighted that NHS England are today supporting the need for all of us to look at what we can do to minimise it.
"Loneliness is no longer just a personal misfortune but has grown into a social epidemic.
"If we can tackle it effectively we can make Britain not just a happier but also a healthier country in which to live."
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