Arianna Huffington tells Elon Musk to sleep more, 'it's not an option,' he says in a 2:30 am tweet

Tesla Inc. chief executive Elon Musk is not sleeping.  

On Friday, media mogul and Musk's acquaintance Arriana Huffington wrote an open letter addressed to Musk asking him to "change the way you work to be more in line with science around how humans are most effective."

Huffington, a “huge admirer” of Musk and author of the 2016 book, “The Sleep Revolution: Transforming Your Life, One Night at a Time,” said his habit of overworking doesn’t help him or his company.

"You need it, Tesla needs it and the world needs it," she wrote. 

Musk, who last week acknowledged exhaustion from overwork as he deals with the aftermath of a market-rattling tweet on taking Tesla private, said that it's simply not an option. 

Musk replied, at 2:30 am: "Ford & Tesla are the only 2 American car companies to avoid bankruptcy. I just got home from the factory. You think this is an option. It is not."

The SpaceX founder told the New York Times last week that he has been working a lot — up to 120 hours a week lately -  as part of an "excruciating" 2018 work schedule, which is taking its toll on his physical and mental wellbeing.

Huffington, who is the co-founder of the Huffington Post and is a board member of Uber Technologies Inc., has a new startup, Thrive Global, which is focused on health and wellness.

As per reports, he often has to take Ambien, a potent sedative, which helps him sleep. In a tweet last year, he wrote: "A little red wine, vintage record, some Ambien ... and magic!"

"This past year has been the most difficult and painful year of my career," Musk told the New York Times in an interview Thursday. "It was excruciating."

Tesla shares tumbled Friday after the Times interview was published, and are now down almost 2% this year. 

The stock has lost more than 20% of its value since Musk tweeted earlier this month that he was thinking about taking the company private. That tweet also triggered an investigation by the Securities and Exchange Commission.