American golfer Ben Griffin says he “overdosed” on creatine at the start of the final round of the BMW Championship.

Griffin, who is a contender for a Ryder Cup spot, says he accidentally swallowed a “large rock” of the supplement in his water bottle.

The 29-year-old said he was “getting super shaky” and felt like he “had tremors”.

He four-putted the par-four first hole and then hit his tee shot on the second hole out of bounds.

The world number 17 was six over par for the first three holes but recovered to card a one-under 69 including seven birdies and finished in a tie for 12th on three under.

“I don’t think I’ll be taking too much creatine in the future,” he said, adding the amount he’d accidentally taken was “probably not a healthy amount”.

Griffin, who finished in the top 10 at this year’s PGA Championship and US Open, said he usually takes 15mg of creatine daily.

Creatine helps improve performance, boost recovery and support strength development.

“I’ve taken it on the golf course before. It’s fine,” Griffin said.

“I started taking it after my second shot and I accidentally swallowed one of the big rocks in my water bottle.”

He added: “Luckily, my caddie stepped in and made me chug a whole [bottle of] water and tried to calm down a little bit. I hit the other one in play and then I was fine.

“I went about my day and got it back to under par. But, yeah, pretty crazy story.”

Griffin is ninth in the US Ryder Cup rankings and would need to rely on being one of Keegan Bradley’s captain’s picks to make next month’s event in Bethpage Black, New York.