doc vs Dr.

doc and Dr. both are nouns.

Word	Noun	Adjective	Verb	Adverb
doc	Yes	No	No	No
Dr.	Yes	No	No	No

As nouns, doc and Dr. are synonyms defined as:

Other synonyms of doc include doctor, MD, medico, physician.

doc (noun)	Dr. (noun)
a licensed medical practitioner	a licensed medical practitioner
	a person who holds Ph.D. degree (or the equivalent) from an academic institution