Inequalities are particularly stark in some African countries
Life expectancy between the world's richest and poorest countries can vary by more than 40 years, a report shows.
The World Health Organization examined primary health care systems around the world, and uncovered huge inequalities and inefficiencies.
It warns shortcomings have left the health status of different populations, both within and between countries, "dangerously out of balance".
The report calls for action to bolster primary care and tackle unfairness.
BIG THREATS TO HEALTH
The World Health Organization report highlights three ills of life in the 21st Century:
Globalization of unhealthy lifestyles
Rapid unplanned urbanization
Ageing of populations
The WHO warns these contribute to a rise in chronic diseases, like heart disease, stroke and cancer, and create new demands for long-term care
Margaret Chan, WHO director-general, warned that doing nothing was not an option - and said focusing on primary care was the best way to affect significant change.
She said: "A world that is greatly out of balance in matters of health is neither stable nor secure."
The WHO report found striking inequalities in health outcomes, access to care, and what people have to pay for care. It said the differences were more stark today than 30 years ago.
For instance, of the estimated 136 million women who will give birth this year, around 58 million will receive no medical assistance during and after childbirth - potentially putting their lives at risk.
Globally, annual government expenditure on health varies from as little as $20 per person to well over $6,000.
For 5.6 billion people in low and middle-income countries, more than half of all health care expenditure is through out-of-pocket payments, pushing many people below the poverty line.
The report finds that huge differences occur within countries - and sometimes within individual cities.
In Nairobi, for example, the under-five mortality rate is below 15 per 1,000 in the high-income area. In a slum in the same city, the rate is 254 per 1,000.
The report warns that too often health care focuses on state-of-the-art technology and specialist care, when giving a greater priority to primary care specialists, such as general practitioners, was likely to be more productive, particularly if they concentrate on preventative medicine.
WHO estimates that better use of existing preventive measures could reduce the global burden of disease by as much as 70%.
The report warns that health systems will not naturally gravitate towards greater fairness and efficiency - instead politicians must take concrete action to promote effective primary care.
Dr Chan said: "We are, in effect, encouraging countries to go back to the basics.
"Viewed against current trends, primary health care looks more and more like a smart way to get health development back on track."