A 67-year-old Victorian man developed cyanide poisoning from taking regular doses of apricot kernel extract.

According to the journal BMJ Case Reports, the poisoning was discovered after he went under anaesthetic for routine surgery.

He had abnormally low levels of oxygen in his body when he was under anaesthetic. Blood tests later showed he had high levels of cyanide.

The man, who hasn’t been named, said he had been taking two teaspoons of home-made apricot kernel extract every day for the past five years as well as three tablets of Novodalin, a herbal fruit kernel supplement.

This meant the man was taking nearly 17.32 milligrams of cyanide every day, which is enough to raise his blood cyanide to around 25 times above acceptable levels.

Apricot kernel extract is a popular complementary medicine and is marketed as a preventative medicine for cancer.

The man, despite being warned of the risks of cyanide toxicity, chose to continue with his fruit kernel food supplements.

"Physicians should be aware that self-prescription with complementary medicines can result in potentially harmful toxicities, and may be more common than currently understood," wrote the doctors from Alfred Hospital in Melbourne.