The American won gold at London 2012 and three years later faced a life away from the track after being diagnosed with a rare kidney disease.
He had a transplant in 2015 just after claiming bronze at the Beijing world championships and a year later just missed out on a place in the US team for the 2016 games in Rio.
A year on from that disappointment, the 31-year-old reached the final. But he was left behind by Omar McLeod who took gold, Sergey Shubenkov and Balazs Baji who claimed the silver and bronze respectively.
“Of course it feels like a victory,” said Merritt. “I am not meant to even be running so to be here in the final is a blessing.
“I’ve only been back in top competition for a year. I finished well and have put in some good performances.”
Merritt was initially diagnosed with the rare congenital kidney disease called collapsing focal segmental glomerulosclerosis (FSGS) in 2013.
His sister, LaToya, donated her kidney to help his recovery and she was in the Queen Elizabeth Stadium to watch the final with their mother. “That they’re here makes it extra special, said Merritt. “Without LaToya I wouldn’t even have had the chance to run again. Of course it would have been great to win a medal in front of them but I had a bad day.
“I’m not the only champion athlete to have suffered that here. Usain Bolt got a bronze in the men’s 100 metres and Elaine Thompson didn’t even medal in the women’s 100m.”
Merritt said he believed he had the potential to return to the top of his sport and added: “There’ve been a lot of results that haven’t been the norm here and that is because there are a lot of new faces coming through and changing things around. That can be only good for the sport.”