"Ian felt like he would lose his job if he told the truth," Ms Gibbons told Vanity Fair. "Ian was a real obstacle for Elizabeth. He started to be very vocal. They kept him around to keep him quiet."
The magazine revealed how Holmes defied the advice of medical experts, her former professor and even Dr Gibbons himself, building a multibillion-dollar company on a technology that was "more of an idea than a reality".
Holmes raised more than half a billion dollars from investors hyping Theranos' "revolutionary" blood testing technology, which she claimed could test for hundreds of diseases with a single drop of blood from the finger.
"I told her, I don't think your idea is going to work," Stanford medicine professor Phyllis Gardner told Vanity Fair, explaining inherent unreliability of pinprick blood tests.
Dr Gibbons was brought in to attempt to make the technology a reality, to no avail, while Holmes went about raising ever more funding.
By early 2013, when Theranos was preparing to open "Wellness Centers" in pharmacies across the country, the chief scientist was desperate.
Vanity Fair reports that on May 16, 2013, Dr Gibbons was at home with his wife when one of Holmes' assistants rang. "Elizabeth wants to meet with me tomorrow in her office," he told his wife. "Do you think she's going to fire me?"
Later that evening, he attempted to take his own life. He died in hospital a week later.
According to the magazine, when his wife called Holmes' office to explain what happened, her secretary was "devastated and offered her sincere condolences", telling her she would let Holmes know immediately.
"But a few hours later, rather than a condolence message from Holmes, Rochelle instead received a phone call from someone at Theranos demanding that she immediately return any and all confidential Theranos property," Vanity Fair wrote.
Lawyers for Theranos have previously denied the scientist's work or technology failures at the company had anything to do with his suicide.
Theranos is under investigation by a who's who of US regulators, including the Food and Drug Administration, the Centers for Medicare and Medicaid Services, the Securities Exchange Commission, the US Attorney's Office and the FBI.
The company is also facing two class-action fraud lawsuits, and Holmes herself has been banned from owning or running a medical laboratory for two years.
Holmes, however, has doubled down, refusing to acknowledge any problems. "Elizabeth Holmes won't stop," Prof Gardner told Vanity Fair. "She's holding on to her story like a barnacle on the side of a ship."
Where to get help
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.
