DES MOINES — Senator Bernie Sanders on Monday released three letters from doctors declaring him healthy, nearly three months after he had a heart attack while campaigning in Las Vegas, and disclosing that he no longer needed some medications relating to the attack.

One of the letters, dated Dec. 28 and signed by Dr. Brian P. Monahan, the attending physician of Congress, characterized Mr. Sanders as “in good health currently.”

“You have been engaging vigorously in the rigors of your campaign, travel and other scheduled activities without any limitation,” Dr. Monahan wrote.

Detailing Mr. Sanders’s recovery from the heart attack, Dr. Monahan disclosed that some of the medications he initially required, such as a beta blocker and a blood thinner, have been discontinued “based on your progress.”