Robbie Williams almost died from mercury and arsenic poisoning while on a fish diet.

The former Take That star admits he only got tested by doctors because his wife, Ayda Field, insisted he get to the bottom of a mystery illness.

"I was eating fish twice a day and I've got the highest mercury poisoning the doctor has ever seen," Robbie told British station Radio X. "Do you know what I thought when I heard that? 'I've won!' That's how my ego works! 'I've got the highest... did you say the highest? Thank you'.

"I literally won the mercury award! I got my mercury tested because my wife's neurotic and she gets all sorts of tests all the time. Anyway, thank God! I could've dropped dead of mercury and arsenic poisoning."

Too much exposure to mercury, commonly found in fish like tuna, shark, and swordfish, can damage the brain, and major organs.

Robbie, 46, has since followed a plant-based diet and ditched fish entirely.

“I went plant-based the next day,” he revealed.

Robbie and Ayda, who wed in 2010, share children Theodora, eight, Charlton, six, two-year-old Colette, and baby Beau.