* "Vado" means "I go".
* "Dal" is a preposition meaning "from" or "to" and is used before masculine singular nouns.
* "Dottore" means "doctor".
Therefore, "vado dal dottore" literally translates to "I go to the doctor".
"Al dottore" would be incorrect because it uses the preposition "al" which is used before masculine singular nouns starting with a vowel.