Credit: Zdenek Gazda via Storyful

Hillary Clinton was headed to an emergency room following her frightening collapse at the Sept. 11 memorial ceremony — but detoured to daughter Chelsea Clinton’s apartment to keep details of her medical treatment under wraps, The Post has learned.

Secret Service protocol called for the Democratic presidential nominee to be rushed to a state-designated Level I Trauma Center in the wake of her Sunday morning health crisis, sources said. In Manhattan, that would be Bellevue Hospital.

But a campaign operative decided to change course to avoid having Clinton seen by doctors, nurses and other medical workers who could leak details to reporters, according to a source.

In addition, Clinton’s van was supposed to be escorted by an NYPD detail, but the Secret Service whisked her away from Ground Zero before cops could accompany her, another source said.

The former secretary of state had told police officials that she didn’t want the escort at all, but the NYPD overruled that request, the source added.

NYPD Deputy Commissioner John Miller said Clinton’s “early departure was transmitted in real time by the Secret Service to the NYPD.”

“There was no lack of communication, nor diminution of security,” he added.

The campaign initially claimed that Clinton left the 15th annual observance at Ground Zero because she “felt overheated” — before revealing hours later that she was actually suffering from a bout of pneumonia diagnosed Friday.

In a statement released by the campaign, Clinton’s personal physician, Dr. Lisa Bardack, said she examined the candidate at her home in Chappaqua, and pronounced her “recovering nicely” after becoming “overheated and dehydrated.”

Campaign spokesman Glen Caplin said the Clinton team “disputed the account” and released a statement saying:

“As soon as she got into the vehicle, she was feeling fine. Her preference was to go to Chelsea’s. Based on an assessment of her condition and after having conferred with her physician, the staff and the Secret Service thought it was appropriate.”

Appearing on CNN Monday evening, Clinton said she did not disclose her diagnosis last Friday because she “didn’t think it was going to be that big of a deal.”

Clinton went on to explain that the illness started out as a nagging cough that she supposed had been due to seasonal allergies. When the cough did not subside, she decided to see a doctor.

Both Clinton and Republican rival Donald Trump — who has repeatedly questioned whether Clinton is healthy enough to lead the nation — promised on Monday to release more medical information in the wake of her caught-on-camera collapse.

Clinton spokesman Brian Fallon said Bardack was preparing “additional medical records” to be made public “in the next couple days.”

“I can attest that it is the case that there is no other undisclosed condition. The pneumonia is the extent of it,” he told MSNBC.

He also admitted that Clinton’s latest health crisis was mishandled by staffers who kept reporters in the dark about her stumbling exit.

“I do think that in the 90 minutes that elapsed, we could have gotten information out quickly,” Fallon conceded. “That’s on the staff. That’s on us. We regret it.”

The New York Times revealed Monday that although close aides and family members were told about the diagnosis, most of Clinton’s staff was left in the dark.

Trump told Fox News that “something’s going on” with Clinton, adding: “I just hope she gets well and gets back on the trail.”

The real estate mogul — who is set to appear on TV’s “The Dr. Oz Show” on Thursday — also said he would release the results of his own recent medical exam.

“I saw what was going on with her and I said, ‘You know, I’m going to go do something,’ and I actually took a physical last week, and probably, I guess this week, will release the results of it,” Trump told CNBC.

Clinton’s spokesman said that in addition to her illness, “several of the senior staff have been afflicted with something or other for the last few days.”

“I was sick for a couple of days. I had the mild form of it,” Fallon said.

The stricken staffers included campaign manager Robby Mook, and two top aides who needed emergency medical treatment — one of whom was taken by ambulance to a hospital emergency room after collapsing from severe dehydration, People magazine reported.

Fallon told CNN that Clinton’s pneumonia, which she is treating with antibiotics, was “not contagious.”

Clinton’s collapse prompted her to cancel a planned trip to California.

Hubby Bill Clinton will appear in her place at Tuesday fundraisers at the homes of “Family Guy” creator Seth MacFarlane and digital tycoon Barry Diller, Deadline Hollywood reported.

Additional reporting by Daniel Halper and Marisa Schultz

Here is another conspiracy theory about Clinton’s health: