The seven-time world champion had a superb performance to move from last place to third in the Hungarian Grand Prix, before moving to second place after the disqualification of Sebastian Vettel.
Hamilton’s relentless performances in the 70-lap race gave him the lead in the Formula 1 world championship.
But afterward, he seemed to be struggling – he needed help getting to the podium and seemed too weak to hold the celebratory champagne bottle.
He was taken to the Mercedes team doctor and then reportedly suffered from dizziness and fatigue.
In a post-race press conference, the 36-year-old said: “I haven’t spoken to anyone in particular about the lengthy COVID, but I think it persists.
“I was really dizzy and everything got a bit blurry on the podium. I’m struggling to stay healthy after what happened at the end of last year, but it’s still a battle.
“I remember the effects of when I had COVID, and the training has been different since then. The level of fatigue you feel is different and it’s a real challenge.
“I try to keep training and preparing as best I can. Who knows what it was today? Maybe it was the hydration, I don’t know, but it was definitely different. “
After the press conference, Hamilton was helped to his feet by race winner Esteban Ocon and a Mercedes staff member.
Hamilton contracted COVID-19 in Dubai in December and has nearly four weeks of competition before his next race in Belgium on August 29.