One of my masseter is larger than the other. After Botox, how long does it take for the muscle to get smaller?

It all depends on dosage here, in korea they start at 60 U per masster. I typically do 30 and then have the patient return 2-3 weeks later for another round.  It can take up to 3 months to see the muscle begin to atrophy.  If you are a night time grinder, you may need higher doses.  Best, Dr. Emer.

After Botox for masseter reduction, the masseter muscle will gradually slim over the course of 3-4 months during which the Botox is active.  If the asymmetry in your jawline was due to muscle asymmetry, it will improve.  However, if the asymmetry is due to bony asymmetry, this will remain.  

Thank you for your question. The masseter muscle injection takes longer than most Botox cosmetic injections to settle, approx. a month. Schedule a follow up with your injector to discuss your concerns. Best,