Some 153,000 travellers needed emergency medical treatment abroad last year - equating to 420 people every day, or one person every three minutes, the Association of British Insurers (ABI) said.
The total medical bill paid by insurers in 2018 was £209 million – the highest figure since 2010.
This meant that medical claims accounted for more than half (52 per cent) of the £399m in travel insurance claims paid out last year.
Cancellation costs made up over a third (36 per cent) of the total, while lost baggage or money accounted for 4 per cent.
A fifth of people still travel overseas without travel insurance, according to the Association of British Travel Agents (Abta), despite the average cost of a travel insurance policy being just £38.
The ABI said air ambulance costs back to the UK can be “jaw-dropping” – typically, £75,000 from Asia, £50,000 from the US and £13,500 from Italy.
The costs of needing overseas emergency medical treatment include:
n £200,000 paid to treat a traveller on a cruise in China who suffered a brain haemorrhage. This included an air ambulance back to the UK from Hong Kong.
n £153,000 for treating a broken arm caused by falling out of a bed in San Francisco. This included paying for the flight back home.
n £137,000 to treat a fractured spine resulting from a bathroom fall in Thailand, including return to the UK.
n £89,000 to pay the medical bill for a holidaymaker who suffered a heart attack while visiting Turkey.
n £78,000 to treat an elderly visitor to Spain for a 23-day hospital stay to treat injuries and trauma following a road crash.
Charlie Campbell, the ABI’s manager of health and protection, said: “For too many people holidays can become horror days, if they fall ill or suffer a serious injury abroad.
“Needing medical treatment can be stressful wherever you are, without the added worry of how you can afford what can be sky-high medical bills.
“Yet the average travel insurance policy costs less than what an average family can spend on drinks and food at the airport and will pay emergency medical bills than can easily run into six figures.”
He continued: “Also, if we leave the EU without a deal then the European Health Insurance Card (EHIC) will cease to apply, making travel insurance even more vital.”