We told you earlier today that Hillary Clinton  left a 9/11 ceremony early this morning and that video appeared to show the Democratic presidential nominee struggling to get into a waiting van.

Her campaign later said she was "overheated."

We may now know why: She has pneumonia.

"Secretary Clinton has been experiencing a cough related to allergies. On Friday, during follow up evaluation of her prolonged cough, she was diagnosed with pneumonia," her doctor, Lisa Bardack, said. "She was put on antibiotics, and advised to rest and modify her schedule. While at this morning's event, she became overheated and dehydrated. I have just examined her and she is now re-hydrated and recovering nicely."

The campaign's statement said Clinton was examined at her home in Chappaqua. The campaign has not yet said if she will maintain her early week schedule, which was to have Clinton on the West Coast.