Doctors helped more than 30,000 people to die last year, with a record high for cases of assisted dying and euthanasia in countries where it is legal.
Ahead of a UK vote on legalising assisted dying on Friday, Telegraph data analysis found the number of deaths has doubled in five years.
In some countries, as many as one in 20 deaths are now attributable to assisted dying, according to the findings.
The increase was recorded across countries where assisted dying and euthanasia is legal, including the Netherlands, Belgium, and the US states of California and Oregon.
In Canada, an estimated one in 25 people who died last year were legally killed.
Assisted dying involves giving patients the means to end their own life, usually lethal drugs, while euthanasia is carried out by a doctor, usually by lethal injection.
While legislation was passed in some countries decades ago, numbers are still rising in part because initially strict rules have been watered down and the procedures made more widely available, including to children.