Australian golfer Jason Day, who sent a scare through the US Open when he collapsed due to vertigo on the final hole of his second round, recovered with a brilliant 2-under 68 in the third round to take a share of the lead.

The world number 10, who has a history of dizzy spells, was diagnosed with benign positional vertigo after receiving medical treatment following Saturday’s second round at Chambers Bay.

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Day struggled throughout his round, but managed to keep his concentration, birdieing four of the last seven holes for a 68, to join a four-way tie for the lead.

“The goal was just to go through today and see how it goes,” a fatigued Day told reporters after the round.

Day had been feeling dizzy before the second round collapse.

“I didn’t feel that great coming out early … I felt pretty groggy on the front nine just from the drugs that I had in my system, then kind of flushed that out on the back nine.

“But then … the vertigo came back a little bit on the 13th tee box, and I felt nauseous all day. I started shaking on 16 tee box and then just tried to get it in, really. Just wanted to get it in.”

Warmly applauded by the galleries packed around the par-four opening hole, Day struck his tee shot safely down the fairway.

He parred the first, then missed a putt on the second, and later bogeyed the par-four fourth to drop back to level par for the tournament. He then parred the next five holes to make the turn at level par.

Day made his first birdie of the day on the 10th, but gave the shot straight back at the 11th after missing a tough five-footer for par.

He rallied, however, with a birdie on the 12th, then produced two great up and downs at 13 and 14 to remain 1-under for the tournament.

He used the slope with his tee shot on 15 to run the ball to within 12 feet, then holed the putt to go to 2-under.

Day then drove the green at the 16th, but his ball was in deep grass next to steps – he chipped on to the green and left another 12-footer for birdie just short.

Day appeared to be getting increasingly fatigued as the round went on, but he hit another great tee shot at 17 to set up another birdie putt.

When his ball made the last roll into the cup for a two, there was huge answering roar from the gallery.

Day’s wife Ellie has been supporting him from the sidelines.

The Australian gave himself another chance for birdie on the par-five 18th, and received a huge ovation from the crowd as he walked onto the green.

He then sank the putt, which made Day the leader in the clubhouse at 4-under.

Dustin Johnson (70), Branden Grace (70) and Jordan Spieth (71) joined him on 4-under after 54 holes.

In other Australian results, young Queenslander Cameron Smith held on against a difficult course to shoot a 1-under 69 to put him tied for sixth.

Smith, who shot level par 70s in the opening two rounds, had two birdies and three bogeys on the front nine, but the 21-year-old came home with birdies on the 14th and 17th.

Adam Scott shot a third round 72 to be 3-over, tied for 19th.

John Senden had level par round to stay at 4-over, tied for 23rd, while Geoff Ogilvy had a 5-over 75 to drop to 6-over for the tournament, tied for 39th.

Marcus Fraser shot a 7-over 77 for a three-round total of 9-over 219, tied for 61st.