I should clarify, though...
You would need the 59 modifier every time you bill a code labeled (separate procedure) with a more comprehensive code on the same date, even if they don't seem related, in order for the code to be accepted by commercial payer claims edit software.
A good example is 94150 (vital capacity), with an office visit like, 99213. Vital capacity is not routinely part of the office visit, but without a 59 modifier, insurer's using McKesson's claims edit software will deny 94150. (If you have access to Cigna or BCBS's provider websites, or Availity, you can see the rationale for the denial with their claim edit tools, and you can also see that it will allow payment with a modifier.
I forget other people don't just deal with commercial insurers specifically...sorry...Thinking in commercial-only terms is a habit I forget about having...