One in 10 pensioners is being forced to stay in bed longer to keep warm as a result of rising fuel bills, according to a poll for the Press Association.
Meanwhile one in eight said they planned to stop using some parts of their homes in the cold weather to keep energy bills down.
More than 12,000 people over the age of 50, including almost 8,000 people who have retired, across Britain answered the survey for Saga, carried out for the Press Association.
A third of people said they had been forced to stop heating as many rooms in their homes and 64% of people said they were having to wear extra layers of clothing as a result of rising energy costs.
One in five was planning to cut back on other spending so they could afford to heat their homes.
Just over two-fifths who responded to the online poll said they would struggle more than in the past with energy bills this winter.
An overwhelming majority, 84%, expressed concern about the rising cost of fuel.
Recently the so-called Big Six firms that dominate the energy supply market all announced above-inflation price hikes.
"For some, the fear could mean they won't turn their heating on, and in so doing, risk their own health and welfare.
"Energy is essential so the Government needs to do more to cut back on consumer green levies, put pressure on energy companies for fairer pricing and to develop new fuel sources linked to lowering consumer bills."
Jane Vass, head of public policy at charity Age UK, said: "High energy prices along with poorly insulated homes are some of the factors that cause cold homes - a major cause of excess winter deaths. Those living in the coldest homes are three times more likely to die a preventable death than those living in warmer ones.
"Long term we strongly believe that the only sustainable solution is investment to increase the energy efficiency of our housing stock so cold homes become a thing of the past.
"But there is action older people worried about rising prices can take now. Ofgem's retail market review that has recently come into practice means that the energy market should be simpler to understand than before and allow people to find the right tariff for them. We would encourage anyone, whether they are struggling to pay their fuel bills or not, to shop around to ensure that
they are receiving the best deal that they can."
The rising cost of energy has featured high on the political agenda since Labour leader Ed Miliband's pledge to freeze energy prices for 20 months if he wins the 2015 general election.
But Deputy Prime Minister Nick Clegg dismissed the Labour plan as a "con" which would result in price hikes before and after it was introduced.
Labour's shadow minister for public health Luciana Berger said: "This survey shows the desperate lengths older people are going to in order to keep warm in David Cameron's Britain.
"We have already seen a 40% spike in the number of people suffering from hypothermia on this Government's watch. Ministers urgently need to act to help people struggling during the winter.
"Too many older and vulnerable people lose their lives every year due to living in homes that are too cold. Many more will be forced to choose between heating and eating because of this Tory-led Government's failure to tackle the cost of living crisis and stand up to the big energy companies.
"That's why Labour will freeze gas and electricity prices and reset our broken energy market."
A Department of Energy and Climate Change spokeswoman said: "The Government is tackling fuel poverty and helping vulnerable households through schemes like the Warm Home Discount which will help two million households this year, including more than one million low income pensioners who will receive £135 off their bill.
"There are ways in which householders can make their homes more energy efficient. In 2013, we saw over 300,000 energy efficiency measures installed in around 273,000 properties through Government's Green Deal and Energy Company Obligation schemes to help insulate people's homes."
A spokesman for Energy UK, which represents the big six suppliers, said: "No one should have to resort to staying in bed longer or only using parts of their home to keep warm, your energy company wants to help, you just need to get in touch.
"Energy companies have offers, discounts, schemes and trust funds to help their most vulnerable customers and can advise on finding the best deal to suit your personal circumstances.
"Help is there, contact your supplier immediately or the free and confidential Home Heat Helpline on 0800 336699 for advice and information on the support you might be eligible for."