Six-time Olympic sprint champion Usain Bolt insists he is "clean" in the wake of recent failed drugs tests by fellow Jamaican athletes.
Compatriots Asafa Powell and Sherone Simpson recently tested positive as did the USA's Tyson Gay, the fastest man in the world this year.
Bolt, who will race in Friday's London Anniversary Games, said: "I'm clean.
"But you have to be very careful as an athlete because right now there are a lot of things on the banned list."
The Jamaican added: "You might not know and you have to keep up to date with this kind of thing. It's kind of hard, but that's why you have a team to make sure.
"For me I get tested all the while. I got tested the day before yesterday, it's just part of the routine. "
The 26-year-old 100m and 200m world record holder pointed to his success as a junior athlete as evidence of his innocence.
"If you were following me since 2002 you would know that I've been doing phenomenal things since I was 15 years old," he said.
"I was the youngest person to win the world juniors at 15. I ran the world junior record in 19.93 at the age of 18. World youth record at 17.
"I have broken every record there is to break in every event I have ever done. For me, I have shown I was always going to be great."
Powell tested positive for the banned stimulant oxilofrine at the national trials last month, and Bolt sent him a text message soon after.
"I didn't want to bombard him with questions," said Bolt. "I told him, 'Sorry to hear what was going on.' And he said, 'Yes, it's kind of rough, it's hard."'
Gay and Powell are still waiting for the results of their 'B' samples, and Bolt was keen to avoid speculation.
"I think there are a lot of details left to be discussed," he said.
The recent spate of positive drug tests has put the focus back on a sport that has been dogged by doping scandals in the past.
"It's going to set athletics back a little bit, but as a person I can't really focus on this," he added. "I still have the World Championships, everyone is stepping up their game, so I have to really focus on that.
"I am just trying to work hard, run fast and hopefully help people forget what has happened and just move on."
Bolt was speaking on the same day a Jamaica football player tested positive for a banned substance after a World Cup qualifying match against Honduras.
The Jamaica Football Federation said it was notified by Fifa that a "member of the Jamaican squad returned an adverse analytical finding on his urine sample" after the 11 June game.
Bolt became the first athlete to retain the 100m and 200m crown at the 2012 London Olympics last summer and then won his third gold of the Games when he anchored Jamaica's sprint relay team to a sensational world record.