"I feel fit; that's the first thing, because otherwise I would not come here," the Russian told press at Madrid.
"So I felt some sickness symptoms. It was like a strong cold, you know, or something like this. Had some nose and throat blocked a little bit, weakness for few days but not more than that.
"Coming back was not easy first four, five days especially laying ten days in your bed at home also. I feel like I had a good one week and a half of practice."
Medvedev officially returned to action on Sunday for a doubles match alongside Marcelo Demoliner. Together, they knocked out Monte Carlo finalists Daniel Evans and Neil Skupski in straight sets.
Medvedev was preparing to play the Rolex Monte-Carlo Masters when he tested positive for COVID-19 (Getty Images).
While he's pleased he is back on court, he would still prefer it was on a different surface. An ATP Finals champion and finalist at the Australian Open and US Open, he's yet to win a title on clay courts.
"I think my shots, my movement, my physical appearance doesn't suit clay," he said. ''First week when I come on clay, I hate everything around me. I just hate to be on the court, and that's very rare for me. Then I get used to and it starts to be better. The big thing that motivates me is that I know that I'm capable to win matches."
Medvedev defeated Novak Djokovic on his way to reaching the Monte Carlo semifinals in 2019 and noted, "Two years ago I beat some really good guys. Was in really good shape. So I know that I'm capable.
"Just need to always find this confidence and this feeling which is tougher for me to find on clay than on hard courts."
The high altitude of Madrid also allows players to put more pace on the ball, which he likes.
"I think that can help," said Medvedev. "It's more comparable to hard courts here in Madrid."
Medvedev is No.3 in the rankings.