Donald Trump says "it's good to be President" because it gave him access to America's best doctors and use of a "miraculous" drug not yet available to the public.
Speaking on Fox News - his first on-camera interview since testing positive for Covid-19 - Trump said the virus had left him feeling weak.
Fox contributor Dr Marc Siegel earlier promised to "conduct a medical evaluation and interview" with Trump.
And he started the on-air medical examination by asking Trump what the President's "chief complaints" or main symptoms had been when he first fell sick.
"I didn't feel very strong, I didn't feel very vital, I didn't feel like the President of the US should feel," Trump said.
However, his condition swiftly improved after being given a transfusion of an experimental drug made by Regeneron Pharmaceutical, he said.
Trump said he was now feeling good and no longer taking medication.
The interview came amid persistent speculation about the president's state of health - and after a phone interview with Fox News host Sean Hannity in which he repeatedly stopped to cough and catch his breath.
It also comes as Trump says he will be back on the campaign trail this weekend despite concerns about the risk of spreading the infection.
Trump said his initial diagnosis with Covid-19 came after he felt began to feel off.
He said he didn't have trouble breathing, but did feel tired.
"(I) didn't have that same energy level," Trump said.
"My life is based a little bit on energy and you didn't have it."
From there things could have gone "bad", Trump said.
"But I got lucky with a certain medicine, I took a certain medicine that was very miraculous to me," he said, referring to Regeneron's drug.
Regeneron earlier said it supplied a single dose to Trump - given through an IV - at the request of the President's physician.
Trump was then taken to the Walter Reed National Military Medical Centre for monitoring.
The new Regeneron drug is in late-stage testing and its safety and effectiveness are not yet known. No treatment has yet proved able to prevent serious illness after a coronavirus infection.
Trump said he began to feel better within 24 hours after using the drug and thought he could have left hospital at the time.
He said he now wanted to give it for free to anyone else suffering from Covid-19, who needed it.
He also praised his doctors.
"I have a lot of respect for these doctors, they're really thebest doctors in the world," he said.
"And Walter Reed, I've seen the work they do with the military and people coming in so badly injured."
This meant he even listened to the doctors' advice.
"Generally I wouldn't, but I did tend to listen to this group," Trump said.
He said he was now "basically" medication free, ending his last round of drug treatments eight hours ago.
That included responding "well" to a steroid treatment that had been known to have side-effects, he said.
Earlier, eople close to Trump were concerned his judgment was being affected by the one of the drugs used to treat his Covid-19 infection, according to news reports citing anonymous sources.
Trump's doctors have confirmed he was being treated with dexamethasone, a powerful steroid which can affect mood, causing euphoria and in some cases psychiatric effects including feelings of grandiosity or mania, after being flown to the Walter Reed military hospital in Maryland last week as his virus symptoms worsened.
He returned to the White House on Monday after a three-day hospitalisation, where his behaviour – including a car ride outside to wave at supporters followed by a barrage of all-caps tweets – had reportedly concerned some of those around him, including his son Donald Trump Jr, according to Vanity Fair.
The left-wing publication's Gabriel Sherman, citing "two Republicans briefed on the family conversations", said Don Jr had told friends he had tried lobbying Ivanka Trump, Jared Kushner and Eric Trump to convince the President he needed to stop acting unstable.
"Don Jr has said he wants to stage an intervention, but Jared and Ivanka keep telling Trump how great he's doing," a source allegedly told Vanity Fair.
"Don said, 'I'm not going to be the only one to tell him he's acting crazy.'"
On Tuesday, Trump abruptly called off coronavirus stimulus relief talks with Democrats until "after the election", saying House Speaker Nancy Pelosi was "not negotiating in good faith" and that he was instructing his team to focus on the Senate confirmation of Supreme Court nominee Amy Coney Barrett instead.
The surprising move caused the stock market to plummet and was labelled a tactical mistake even by some Republicans, who argued he should have allowed Democrats to bear responsibility for the stalled negotiations, but instead had made it appear he had abandoned voters suffering due to Covid-19 lockdowns.
In a follow-up tweet, Trump appeared to have realised his mistake. "If I am sent a Stand Alone Bill for Stimulus Checks ($1200), they will go out to our great people IMMEDIATELY. I am ready to sign right now. Are you listening Nancy?" he wrote.
The New York Times, also without citing sources, reported that "some White House staff members wondered whether Trump's behaviour was spurred by a cocktail of drugs he has been taking to treat the coronavirus, including dexamethasone".
The newspaper said Trump had "made calls from the White House on Tuesday and roamed the areas of the presidential residence that had been set up for him" but was "described as itching to get back into the Oval Office and show that he was in charge".
Sean Conley, Trump's doctor, said on Thursday the President had "completed his course of therapy for Covid-19 as prescribed by his team of physicians" and would be ready for public engagements by Saturday.