A new survey by Macmillan Cancer Support found that almost a quarter of those living with the disease have worn or expect to wear outdoor coats inside the house to stave off the cold, with one in five opting to just stay in bed.
Worryingly, seven per cent of respondents said they have already got, or will have to get into debt so that they can pay their fuel bills.
The charity warns that cancer patients often feel the cold worse than others but often keep the heating down in an attempt to save money.
Heidi, a 37-year-old Cheshire woman with terminal breast cancer, is one of those who struggles to keep warm in the cold weather.
She said: "My immune system is so weakened but I can't afford to keep warm all the time. I'm always in debt and behind payments for my energy bills. It makes me panic.
"I have to cover myself in blankets and hot water bottles to help keep my joints warm.
"I wish the government would realise that it is not just the old who get cancer and suffer the cold."
Macmillan said it has popular support for its call, with 89 per cent of people agreeing that vulnerable cancer patients should be supported through the Government's proposed Warm Home Discount scheme, which requires energy providers to provide a rebate for vulnerable customers.
Ciaran Devane, chief executive at Macmillan Cancer Support, said: "Paying fuel bills is one of the biggest worries for cancer patients.
"It is unacceptable that in today's society cancer patients, who feel the cold more and spend long periods of time at home, are still freezing but are too scared to put the heating on because of rising fuel bills."