Mary Lou’s question: “Why is it that MD does not have a period after the M. and D. as this is a title?”
BizWritingTip response: The rule for abbreviations is that if they are composed of all capital letters, you do not use periods with them.
SOPs (standard operating procedures)
Exception: Abbreviations that are geographical, refer to a person, or are a single letter, do have periods.
John A. Macdonald
S. (but SW is correct — two letters)
Most abbreviations made up of lowercase letters or that are a mixture of upper and lowercase do contain periods.
i.e. or e.g.
Mr. or Mrs.
However, according to The Canadian Press Caps and Spelling mixed abbreviations that start and end with a capital letter do not contain periods.
U of T
Aren’t you glad you asked?