British running legend Mo Farah said on Thursday he is aiming for an April return from injury to road racing, adding he is covering more miles now than 20 years ago as he bids to extend his career.

The 39-year-old four-time Olympic gold medallist withdrew from Sunday's London marathon because of injury and said there would be no "rash decisions" about racing again.

"I hope to participate again in the future. Honestly, training was going well," Farah told reporters at the World Innovation Summit for Health in Doha, where he spoke about the need to boost mental health help for athletes.

He said his problems started about two weeks before the London race.

"I felt a little bit my hip, a bit sore and that was me out," he said.

Farah said he would go to Ethiopia for three months of training in January. When asked about his next competitive race, he said: "I think April. It depends."

"It's not making rash decisions in terms of 'I just want to race'. I think you have to be in the right frame of mind and the body has to be right."

Farah, who quit track events this year, had no particular race in mind. He said he just wanted to "tick the box" on winning another major marathon to add to his 2018 Chicago victory.

"I'm definitely retired from the track because I've achieved everything there is to achieve," said Farah, who also has six world titles.

"There's nothing that you can improve or nothing more you could do. And that's the reason why I wanted to go to the road because I believe the roads -- I didn't know what I was capable of."

Farah said he is now running between 120 and 125 miles (195-202 kilometres) a week, against 100 miles two decades ago.

"About four weeks ago, it was the highest I have done for a while. It was close to 138 (miles). And you couldn't keep that going."

"It has to be quality over quantity," he added.