Up to 100,000 lives could be saved every year if a known drug were given to seriously bleeding trauma patients, says a report from a global trial.
The research reported in The Lancet shows that tranexamic acid (TXA), which helps blood to clot, could lower the risk of dying by 15%.
Developing countries would benefit most from this treatment, say researchers after studying 20,000 patients.
Each year 600,000 injured patients bleed to death worldwide.
World Health Organisation figures show that nearly six million people die each year from injuries, which accounts for 10% of the world's deaths.
Most of those injury deaths occur in developing countries, where deaths from road traffic crashes and homicide have been steadily increasing. Almost half of those deaths are caused by bleeding.
Although previous smaller trials had shown that TXA reduced bleeding in patients undergoing major surgery, this was the first trial to test its effect on injured patients with severe bleeding.
The trial involved patients from 274 hospitals across 40 countries.
These included victims of traffic accidents, shootings, stabbings or land mine injuries.
The patients were injected with 1g of TXA within a few hours of being injured, followed by another 1g in a drip over the next eight hours, or a matching placebo.
After studying the numbers of deaths in hospital within four weeks of injury, researchers found that TXA reduced the chances of death, due to massive blood loss, by one sixth.
Ian Roberts, professor of epidemiology from the London School of Hygiene and Tropical Medicine, led the CRASH-2 international trial. He said it showed a "highly significant reduction in risk of dying".
"The large number of patients treated in very different healthcare settings around the world means we can be sure that prompt use of TXA will be of benefit to trauma patients in all kinds of facilities," he said.
The trial also showed no evidence of complications or unwanted clotting, which doctors had feared.
Researchers estimate that TXA could prevent up to 100,000 deaths every year across the world. In countries like India and China it could save about 12,000 lives each year, they predict.
Two thousand deaths a year could be saved in the United States and more in Europe. In the UK, where about 1,800 people die from bleeding after injury each year, researchers say TXA could cut this figure by about 280.
Addressing the practicalities of making the drug available worldwide, Professor Roberts said: "TXA is one of the cheapest ways to save a life there is".
The poverty problem
TXA costs about £3 per gram; it is easily administered and does not need to be refrigerated, he says. It can also be manufactured by a number of different companies.
The authors of the trial report recommend that tranexamic acid, should be available to doctors treating trauma patients in all countries, and should be considered for inclusion on the WHO List of Essential Medicines.
Dr Etienne Krug, director of violence and injury prevention and disability at the World Health Organisation, said that doctors needed to be aware of the trial results.
"We want to avoid injuries happening in the first place but we also need to strengthen the trauma response. Death and serious injury throw families into poverty, so the problem affects hundreds of millions every year worldwide."
The trial was jointly funded by the National Institute for Health Research, part of the Department of Health, the drug company Pfizer, the BUPA Foundation and the JP Moulton Charitable Foundation.
UK health minister Earl Howe said: "This is a great example of how important research can help the NHS save more lives and spread best practice around the world."