[Your letterhead, if desired; if not, your return address]
[Date of letter-month, day, and year]
[Recipient's first and last names]
[Street or P.O. box address]
[City, State ZIP code]
Dear [recipient's name]:
I just wanted to write and let you know how much my family and I appreciate your medical care. The recent illnesses that we experienced were really stressful and difficult, as you know, and we so appreciate your competent and reassuring care. You made a major difference and helped the situation to turn out so positively. We also really appreciate you being available when I needed to call you a couple of times during the evening and on the weekend.
Thank you again for being there for us and for helping us get through a rough patch in our lives. We appreciate you immensely.
[Sender's first and last names]