The Commonwealth Games has witnessed arguably its most gripping and distressing moment when Scotland's Callum Hawkins collapsed while leading the men's marathon 2 kilometres from the finish line.

Hawkins had looked set for a comfortable victory when he opened a lead of more than two minutes over Australia's Michael Shelley on the Gold Coast.

But in the closing kilometres Hawkins began to be affected by the heat, with the temperature having reached 28 degrees by the late stages of the race.

Michael Shelley of Australia (right) passes Callum Hawkins of Scotland after he collapsed. ( AAP: Tracey Nearmy )

He started swaying towards the roadside barrier and even crashed into the spectator area next to the course just ahead of the Sundale Bridge in Southport.

The 25-year-old got back on his feet but was clearly in discomfort as he struggled to make his way across the bridge and more than once he needed to use the roadside barrier to prop himself up.

Hawkins had only just passed the 40km mark when he crashed into the bridge railing and collapsed on the road, unable to get up.

At this stage the official lead over Shelley was two minutes and three seconds. Hawkins was forced to watch the Australian, who did not look at his opponent as he lay on the ground, run by on his way to a second consecutive Commonwealth Games gold medal.

It was little surprise Hawkins could not finish the race, such was his physical distress, and after race officials attended to him on the course he was taken to hospital for a medical review.

Shelley admitted he too was struggling, especially with the wind playing havoc along with the hot conditions.

Medical staff cool down Callum Hawkins after his collapse in the Gold Coast heat. ( AAP: Tracey Nearmy )

"I saw him (Hawkins) at about the 40km mark and I thought 'jeez, I might still be a chance here'," Shelley said.

"Then a couple of hundred metres later the legs started giving me the little wobbles and I was like 'oh jeez, I could be on the road myself in about 500 metres'.

"So getting up that last little hill was brutal and I saw the wind start to get me as well."

Friends along the course had alerted Shelley to the fact Hawkins was in distress, while he was dealing with his own physical demons.

"I was starting to go myself," Shelley said.

A paramedic treats Callum Hawkins after his collapse during the marathon. ( AAP: Tracey Nearmy )

"I was starting to get little cramps in my hand, stuff like that. So it was quite difficult at the time."

In his mind Shelley had settled for the silver medal, as the "jelly legs" took effect.

He had noted Hawkins had picked up the pace considerably between the 25km and 30km checkpoints.

"I was like 'oh jeez, here we go. This could be a long day at the office'," Shelley said.

Scotland's Robbie Simpson finished third, despite the fact he "could feel the legs going".

He was disappointed for his teammate after seeing the state he was in when he went past at the 40km mark.

"He was going so well," Simpson said.

Callum Hawkins has been taken to hospital, but Scottish officials hold no concerns over his health. ( AAP: Tracey Nearmy )

"I really felt [for him] passing him lying on the ground like that."

Commonwealth Games organisers responded to questions surrounding the time it took to get medical help to the Scottish athlete.

GOLDOC CEO Mark Peters said it wasn't possible for medics to be positioned on "every kilometre" of the track but said officials would look into whether the response time was reasonable.

"We need to check the facts out…obviously the health of the athlete is absolute prime," he said.

Mr Peters said there was "no reason" there would be deliberate delays.

"Sometimes medical people arrive and the athlete has to make a decision as to whether they want to go on or not. I understand that was part of a discussion at a point in time, because incredibly athletes in whatever state they are want to finish," he said.

Mr Peters said he was worried about the actions of some spectators when Hawkins collapsed.

"I was also concerned about the behaviour of a small number of bystanders who chose to take images. This is not in keeping with the spirit of GC2018," he said.

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Shelley, who is based on the Gold Coast, said he does not believe any athlete could prepare for the conditions the marathon field had to face on Sunday.

He praised the crowd lining the street course on the Gold Coast for getting him over the line.

"I'm stuffed," Shelley said.

"The emotion and the crowd really got me home in the last couple of kilometres."

Shelley ran a time of 2:16.46 to win his second Commonwealth Games gold.

Team Scotland wrote on social media that Hawkins had been taken to hospital for monitoring, but medical staff had "no major concerns" about his condition.

In a later tweet, Team Scotland wrote that Hawkins was sitting up and talking, but was undergoing further tests as a precaution.