Grayson was born to Dr. John Cooke Grayson (a descendant of American George Mason, one of the American Founding Fathers) and Frances Adelena Pettus at Salubria, the Grayson family estate in Culpeper County, Virginia.
He graduated Phi Beta Kappa with a bachelor's degree from the College of William and Mary in 1898.
He studied for three years at the Medical College of Virginia before leaving to attend the University of the South.
After a year there, he received his M.D. as well as his Doctor of Pharmacy.
He interned for a year at Columbia Hospital for Women in Washington, D.C.
After completing his medical studies, Grayson was appointed Acting Assistant Surgeon on July 14, 1903.
He served at the U.S. Navy Hospital in Washington, D.C., continuing to study at U.S. Navy Medical School (from which he graduated in 1904).
He received a second M.D. from the Medical College of Virginia in 1904.
His studies complete, for two and a half years he served aboard the USS Maryland while it was deployed overseas.

In 1907, he was assigned to the Navy's Bureau of Medicine and Surgery and appointed Naval surgeon aboard the Mayflower, the presidential yacht of President Theodore Roosevelt.
He continued in this role during the entire William Howard Taft administration as well.

While attending a dinner party in March 1913, Grayson aided President Woodrow Wilson's injured sister and quickly became a close confidant of the new president, who had grown up in the South.
In 1915, after the death of Wilson's first wife, Grayson introduced Wilson to Edith Bolling Galt, who became his second wife.

Grayson's close personal relationship with Woodrow Wilson led to his commission as a Rear Admiral on August 29, 1916. "
This rapid promotion of Dr. Grayson from Passed Assistant Surgeon with the rank of Lieutenant to Medical Director to the rank of Rear Admiral was unprecedented and was due to his position as White House Physician."
Grayson resided in the White House.
He accompanied Wilson and stayed near him while he attended peace talks in Paris in 1919.

Grayson was involved in the conspiracy to hide the severity of Woodrow Wilson's October 1919 stroke from members of the government and from the public.
Some historians have strongly criticized Grayson's actions, while others have supported them. "
While one might excuse Mrs. Wilson's actions on the grounds of wifely loyalty, Grayson's behavior during these days exceeded the bounds of physician responsibility.
Grayson was using the office of the president of the United States as therapy of his patient."

More of Grayson's documents were donated by his family to the Woodrow Wilson Presidential Library (Staunton Virginia) in 2006.
Researchers have found that these shed more light on the events that took place.

After Wilson left office in 1921, the Navy assigned Grayson to the U.S. Naval Dispensary.
From this position, he continued to attend to Wilson's health.
Grayson was born to Dr. John Cooke Grayson (a descendant of American George Mason, one of the American Founding Fathers) and Frances Adelena Pettus at Salubria, the Grayson family estate in Culpeper County, Virginia. He graduated Phi Beta Kappa with a bachelor's degree from the College of William and Mary in 1898. He studied for three years at the Medical College of Virginia before leaving to attend the University of the South. After a year there, he received his M.D. as well as his Doctor of Pharmacy. He interned for a year at Columbia Hospital for Women in Washington, D.C.
After completing his medical studies, Grayson was appointed Acting Assistant Surgeon on July 14, 1903. He served at the U.S. Navy Hospital in Washington, D.C., continuing to study at U.S. Navy Medical School (from which he graduated in 1904). He received a second M.D. from the Medical College of Virginia in 1904. His studies complete, for two and a half years he served aboard the USS Maryland while it was deployed overseas.
In 1907, he was assigned to the Navy's Bureau of Medicine and Surgery and appointed Naval surgeon aboard the Mayflower, the presidential yacht of President Theodore Roosevelt. He continued in this role during the entire William Howard Taft administration as well.
While attending a dinner party in March 1913, Grayson aided President Woodrow Wilson's injured sister and quickly became a close confidant of the new president, who had grown up in the South. In 1915, after the death of Wilson's first wife, Grayson introduced Wilson to Edith Bolling Galt, who became his second wife.
Grayson's close personal relationship with Woodrow Wilson led to his commission as a Rear Admiral on August 29, 1916. "This rapid promotion of Dr. Grayson from Passed Assistant Surgeon with the rank of Lieutenant to Medical Director to the rank of Rear Admiral was unprecedented and was due to his position as White House Physician." Grayson resided in the White House. He accompanied Wilson and stayed near him while he attended peace talks in Paris in 1919.
Grayson was involved in the conspiracy to hide the severity of Woodrow Wilson's October 1919 stroke from members of the government and from the public. Some historians have strongly criticized Grayson's actions, while others have supported them. "While one might excuse Mrs. Wilson's actions on the grounds of wifely loyalty, Grayson's behavior during these days exceeded the bounds of physician responsibility. Grayson was using the office of the president of the United States as therapy of his patient."
More of Grayson's documents were donated by his family to the Woodrow Wilson Presidential Library (Staunton Virginia) in 2006. Researchers have found that these shed more light on the events that took place.
After Wilson left office in 1921, the Navy assigned Grayson to the U.S. Naval Dispensary. From this position, he continued to attend to Wilson's health.
Cary T. Grayson