Piecing together clues, medical experts suggest Trump could be entering a pivotal phase in his fight against Covid-19.

The White House physician, Dr. Sean P. Conley, said on Tuesday that President Trump was experiencing no symptoms of Covid-19 and doing “extremely well” on his first full day at home since a three-night stay in the hospital.

But outside doctors and medical experts in Covid-19 and lung disease said they were struggling to piece together an accurate picture of Mr. Trump’s health. Far from having vanquished Covid-19, the outside experts said, Mr. Trump is most likely still struggling with it, and possibly entering a pivotal phase in which he could take a turn for the worse.

Dr. Conley said on Monday that Mr. Trump had been prescribed dexamethasone, which some experts saw as a sign that the president could be dealing with pulmonary issues since it is recommended only for Covid-19 patients who have severe or critical forms of the disease.

“Does he have lung involvement? My guess is yes, because they did give him a lot of medications that they would only give to someone who did,” said Dr. Mangala Narasimhan, a pulmonologist and director of critical care services at Northwell Health in New York.