People are being seriously harmed and in some cases killed by overdiagnosis and unnecessary treatment, one of the country's leading specialists warns. Nicholas Jones hears why health workers are being urged to think twice before ordering a test or procedure.

Medicine's ability to help the sick could soon be outstripped by a propensity to harm the healthy.

That's the firm view of Dr John Bonning, the first Kiwi to be elected to head the Australasian College for Emergency Medicine in its 35-year history.

Bonning is also involved with the New Zealand chapter of the international Choosing Wisely movement, started by