To write a letter to a doctor, address him in a formal manner, describe the purpose of the letter, include complimentary sentences, and state your desire to continue being his patient. Send the letter to the doctor's office address instead of his home address.
The format and content of a letter to a doctor depends on its purpose, such as expressing appreciation for the doctor's medical help or requesting a copy of medical records. When writing to express gratitude, state how the doctor helped you at the beginning of the letter. For example, you might explain that you are thankful he provided an accurate diagnosis.
State your confidence in the doctor's skills, knowledge and professionalism, especially if he helped you recover from a serious medical procedure. Saying that you are happy and healthy after the treatment is a good way to convey gratitude.
The last paragraph of the letter should express your desire to consult him again if the need arises and your hopes of finding an equally competent doctor in the future. Make sure to address the doctor properly by writing his first and last name on the envelope, followed by "MD." Alternatively, add "Dr." before his first name if he holds a doctorate.