As Mr. Musk entered President Trump’s orbit, his private life grew increasingly tumultuous and his drug use was more intense than previously known.

As Elon Musk became one of Donald J. Trump’s closest allies last year, leading raucous rallies and donating about $275 million to help him win the presidency, he was also using drugs far more intensely than previously known, according to people familiar with his activities.

Mr. Musk’s drug consumption went well beyond occasional use. He told people he was taking so much ketamine, a powerful anesthetic, that it was affecting his bladder, a known effect of chronic use. He took Ecstasy and psychedelic mushrooms. And he traveled with a daily medication box that held about 20 pills, including ones with the markings of the stimulant Adderall, according to a photo of the box and people who have seen it.

It is unclear whether Mr. Musk, 53, was taking drugs when he became a fixture at the White House this year and was handed the power to slash the federal bureaucracy. But he has exhibited erratic behavior, insulting cabinet members, gesturing like a Nazi and garbling his answers in a staged interview.

At the same time, Mr. Musk’s family life has grown increasingly tumultuous as he has negotiated overlapping romantic relationships and private legal battles involving his growing brood of 𝘤𝘩𝘪𝘭𝘥ren, according to documents and interviews.

On Wednesday evening, Mr. Musk announced that he was ending his stint with the government, after lamenting how much time he had spent on politics instead of his businesses.

Mr. Musk and his lawyer did not respond to requests for comment this week about his drug use and personal life. He has previously said he was prescribed ketamine for depression, taking it about every two weeks. And he told his biographer, “I really don’t like doing illegal drugs.”

President Trump spoke about government spending alongside Mr. Musk and his son, known as X, in the Oval Office in February.

At a news conference with Mr. Trump on Friday afternoon, Mr. Musk was asked about The New York Times’s coverage. He questioned the newspaper’s credibility and told the reporter to “move on.” He later said on social media that he did not use drugs. That evening, President Trump told reporters outside Air Force One that he was not aware of regular drug use by Mr. Musk. “I’m not troubled by anything with Elon,” he said. “I think he’s fantastic.”

As a large government contractor, Mr. Musk’s aerospace firm, SpaceX, must maintain a drug-free work force and administers random drug tests to its employees. But Mr. Musk has received advance warning of the tests, according to people close to the process. SpaceX did not respond to questions about those warnings.