I've taken 50mg zoloft (sertraline) and 20mg propranolol for a few months with no noticeable dizziness, just some fatigue. still need monitoring for interaction?

Caution good but....: Both of these medications are very low doses, especially the propranolol. If you were going to have an interaction, it probably would have happened by now.

Not necessary: While it’s always a good idea to continue to watch and consider the interaction, especially if starting additional medications, a few months should be more than enough time for the interaction to have surfaced.