Now the next seven to 10 days are vital to see how the president's body responds to the latest treatment.
"I came here, wasn't feeling so well. I feel much better now," reassuring words Saturday night from President Trump but Dr. Robert Wachter, chair of the Department of Medicine at UCSF says the president's health remains uncertain.
"We certainly see people that do this and they come up a little bit and the next day they crash. He's got to be watched very carefully. The fact that he was low yesterday means that he is at risk of becoming low again tonight," Dr. Robert Wachter said.
RELATED: President Trump was given oxygen before his admission to hospital: Reports
Dr. Wachter's biggest concern is that President Trump was allegedly given oxygen at the White House, indicating the virus may have affected his lungs.
"Now that his oxygen level is fallen we know that he is at risk of a bad case of COVID-pneumonia," Wachter added. "The key is that his oxygen level was low. Because sometimes some people come to the ER and we slap on a little oxygen and it's not a big deal. But knowing that he did get it because he actually needed it is very important."
[Ads /]
A diagnosis that according to UC Hastings Law Professor Hadar Aviram could potentially change the presidential race.
WATCH: Trump says 'I feel much better,' but doctor says he's 'not yet out of the woods' amid COVID-19
Coronavirus: Trump 'not yet out of the woods,' president's physician says
"This could play either to his determent with people who would be accusing him of downplaying the pandemic and then sort of learning from his own mistakes or he could ride on a wave of sympathy from behind and recover the problems from his current campaign," said Professor Aviram.
[Ads /]
A month from the election there is a question that lingers, "If the 25th amendment is invoked who would be on the ballot?"
"The constitution did not foresee quite this situation, but what might happen is that Mike Pence would take over the presidential duties temporarily while Trump remains on the ballot," explained Professor Aviram.
President Trump is 74 years old and is clinically overweight. Two factors that place him under the high risk category for recovery.
MORE: List of notable figures who've recently announced a COVID-19 diagnosis
"He is not out of the woods and if you take all people of his age and in his situation at this point in the progression you would have to say there is a chance of passing away from this is at least 10%, Now it's not 50% his odds are still with him that he is going to do okay," said Dr. Wachter.
In the past Dr. Wachter has been critical of the president handling of the pandemic, but says that's not influencing his medical opinion.
[Ads /]
Dr. Wachter also suggested for the upcoming presidential debate to be "virtual," pointing to the possibility that President Trump may be contagious in 14 days.
"It wouldn't be unreasonable for him to debate...14 or 15 days after the onset infection I would still worry about the possibility that he is still infectious. Although in general about 10 to12 days after the symptoms you're no longer infectious"