The statement said the Democratic presidential nominee "continues to improve" after a pneumonia diagnosis.
The disclosure came as her Republican rival Donald Trump released health data of his own on a medical chat show.
Clinton aides say she will return to the campaign trail on Thursday after falling ill in public at the weekend.
|Democratic Party's Nominee for US President Hillary Clinton
Both candidates, among the oldest ever to run for the White House, have been under intense pressure to share more medical information.
Health issues have dominated the race for November's election since a dizzy spell forced Mrs Clinton, 68, to leave a 9/11 ceremony in New York on Sunday.
Her campaign said on Wednesday that her physician found her complete physical examination was "normal" and she is in "excellent mental condition".
Dr Lisa Bardack said Mrs Clinton was "recovering well with antibiotics and rest".
|Donald Trump appeared on The Dr Oz Show to discuss his own health
The campaign said she had a chest scan on Friday that showed a "mild, non-contagious bacterial pneumonia".
Mrs Clinton - who has been recuperating at her suburban New York home - was treated with an antibiotic called Levaquin, which she was prescribed for 10 days.
"She continues to remain healthy and fit to serve as President of the United States," concluded Dr. Bardack in his letter.
The physician said Mrs Clinton was up to date on all vaccines, including two given to help prevent pneumonia, Prevnar and Pneumovax.
The letter did not state when she received those vaccines.
Mrs Clinton's blood pressure (of 100 over 70) and total cholesterol (189) were all within healthy levels, according to the letter.
The former Secretary of State also had a normal mammogram and breast ultrasound, said the doctor.
She takes thyroid and allergy medicines and the blood thinner Coumadin, prescribed after she suffered a blood clot resulting from a 2012 concussion.
The blood clot was said to have been in a vein in the space between the brain and the skull behind the right ear.
The complication led Mrs Clinton to spend a few days in hospital and take a month off from her job at the State Department.
Mr Trump, meanwhile, has said he is planning to release details this week of a recent physical.
The Republican White House nominee handed over a one-page summary of that examination while appearing on The Dr Oz Show.
He told the host he is 236lb and 6ft 3in tall, which would make him clinically overweight.
The syndicated television show will not be broadcast until Thursday and the campaign declined to immediately disclose the results.
Mr Trump told a rally in Canton, Ohio, on Wednesday night that he doubted Mrs Clinton would have the stamina to lead one of his events.
He asked the crowd: "You think Hillary would be able to stand up here for an hour and do this? I don't think so, I don't think so."
Mr Trump later said she was "lying in bed, getting better".BBC