Botox for reduction of masseter. How many units are required for a noticeable difference?

Thank you for your question. Botox in the masseter region usually takes longer than in the standard areas to take effect. I tend to use anywhere from 15 units (conservative treatment) to 50 units (for someone with really strong masseters) on each side to get the desired result. It may start within the first week but I tell my patients to wait three weeks before doing a more thorough evaluation. The treatment typically lasts longer than the forehead/crows feet/frown regions. It is also a gradual onset of the return of masseter function. I have tried the masseter injections myself and space the treatments around 4 months apart, but use smaller doses to maintain the effect. I normally know the effects are wearing down when I start to clench my teeth more heavily at night when asleep. Once you stop using Botox, the masseter muscles will return to their original baseline when the effects of Botox wears off completely.

Everyone's facial anatomy and response to Botox differs
and the masseter is no exception. A good starting point is 15-25
units and following up with your provider 2-3 weeks later to determine if
more is needed. Close follow-up is key to determine what amount is
just right for you. Once this is determined, then you can resume to
a less frequent schedule of botox injections since touch-ups will likely
not be needed for subsequent sessions.

The appropriate dosage of Botox for masseter reduction is whatever dose will achieve full relaxation of the masseter muscle.  Just like any muscle, if it is incompletely relaxed then it will be able to contract and "exercise", and thus will not atrophy and shrink maximally.  For approximately 80% of patients, a dosage of 25 units per side (50 units total) will achieve full treatment.  I typically recommend patients to return 2-3 weeks after their initial treatment to determine if any additional Botox is necessary for full treatment.