Britain lags behind many of its European neighbours and ranks 30th in a global list of countries assessed for health care quality and access.
Experts who analysed death-rate data from 195 nations judged the UK to be on a par with the Czech Republic and Portugal.
The top-ranking country was the tiny principality of Andorra, which scored 94.6 overall on a scale of zero to 100.
At the bottom of the table, scoring just 29, was the Central African Republic.
The UK's health care performance score of 84.6 was better than that of the US, which was awarded 81.3 points, putting it in 35th place.
But Britain was beaten by Finland, Sweden, Spain (all 90) and Italy (89), all of which have similar health systems to the NHS, said researchers.
The study, published in The Lancet medical journal, set out to assess the availability and quality of health care services worldwide from 1990 to 2015.
Researchers created a Healthcare Access and Quality (HAQ) index based on numbers of deaths from 32 causes that could be avoided by "timely and effective" medical care.
Professor Martin McKee (pictured), from the London School of Hygiene & Tropical Medicine, who co-led the study, said: "The UK has made consistent progress since 1990, but with a score of 85, it now lags behind many of its European neighbours, including Finland, Sweden, Spain and Italy, all of which have health systems very similar to the British NHS and so are most directly comparable.
"The gap between what the UK achieves and what it would be expected to, given its level of development, is also wider than in other western European countries."
A breakdown of specific causes of death showed that Britain did well in some areas.
The UK achieved a top score of 100 for treating common vaccine-preventable diseases such as diphtheria, tetanus and measles.
It also earned a high score of 88 for treating cerebrovascular disease. This was probably due to the quality of general practice, leading to the early detection and treatment of blood pressure and better management of stroke, said Prof McKee.
However Britain performed poorly in other categories which included some cancers, an outcome blamed on lack of investment in specialist care. It scored just 58 for the blood cell cancer Hodgkin's lymphoma and 64 for lower respiratory infections.
US lead author Dr Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, said: "What we have found about health care access and quality is disturbing.
"Having a strong economy does not guarantee good health care. Having great medical technology doesn't either. We know this because people are not getting the care that should be expected for diseases with established treatments."
As examples, he pointed to Norway and Australia, which each scored a high-ranking 90 overall. Yet Norway scored 65 for its treatment of testicular cancer, while Australia was awarded just 52 points for non-melanoma skin cancer.
"In the majority of cases, both of these cancers can be treated effectively," said Dr Murray. "Shouldn't it cause serious concern that people are dying of these causes in countries that have the resources to address them?"
From 1990 to 2015, the gap between the best and worst-performing countries grew by almost five points, the study showed.
Overall in 2015, western European countries scored the highest and those in sub-Saharan Africa and Oceania the lowest.
Cape Verde bucked the African trend by finding a place in the middle of the table.
South Korea, Turkey, Peru, China and the Maldives saw some of the greatest improvements in health care access and quality since the 1990s, said the researchers.
The top five performers were Andorra (94.6), Iceland (93.6), Switzerland (91.8), Sweden (90.5), and Norway (90.5).
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