One in eight people in Northern Ireland provided unpaid care for a loved one, census figures showed.
People aged in their early 50s were most likely to be take on the burden, often despite suffering their own health problems, statistics for 2011 showed. Some people sacrificed 50 or more hours a week to looking after family, friends or neighbours.
Catholics were more likely to see themselves as unhealthy, according to the survey, even though they were generally younger than Protestants. Billions of pounds worth of care have been devoted to the sick by informal carers and the system could not cope without them, one academic said.
Dr Dermot O'Reilly from Queens University Belfast warned: "They are sometimes putting their own health at risk by providing unpaid health care. There needs to be more attention paid to carers, more people looking out for the needs of carers."
Northern Ireland has a higher proportion of people with significant life-limitations on activity, poor health and a higher proportion of carers, he added.
"It is important that health policymakers look towards the health of carers; the system would collapse if these people were not providing care," he said.
According to the 2011 census, overall 12% of the population provided unpaid care each week to family members, friends, neighbours or others. Those with long-term health problems or disabilities limiting their day to day activities "a little" were most likely to provide such care (17% compared with 12% of those with no condition).
Approximately one person in eight (12%) of those with long term health problems provided unpaid care, the proportion varying across age groups but peaking at 18% among those aged 50-54. This is because those with elderly partners were themselves more likely to suffer ill health as they got older.
One in 20 people with a life-limiting disability provided 50 hours or more per week, peaking at 7% among those aged 65-69.
Dr O'Reilly said: "We are an ageing population, we have more people not in work and a smaller proportion of the population in work.
"This is what is driving the pushing back of pension age, that is what is driving the increasing level of carers and the people in poor health and the need for long stays in institutions.
"The biggest thing we can do is try to ensure that as a population everybody arrives at old age in a healthy state."
He said 60 or 70 year-olds are generally in better health than they were but added Northern Ireland should aim for levels of good health similar to Japan, where people are renowned for longevity.
Health authorities have warned of the dangers posed by obesity and conditions like diabetes.
The academic added: "It is still a potential threat that the population coming through may actually be less healthy than the generation going through at the minute."