The dosing ranges by muscle size
Your injector will ask you to clench while they feel the muscle at the angle of your jaw. What they are assessing is bulk and how far the muscle extends.
- Small or mildly hypertrophied masseter: 20-25 units per side
- Average masseter: 25-30 units per side
- Strong, visibly enlarged masseter (typical of long-term clenchers and grinders): 30-40 units per side
Men frequently need doses at the higher end, as masseter bulk correlates with muscle mass generally. Patients with a long history of nighttime grinding often have the most substantial muscles of anyone we see.
Doses above 40 units per side exist but are uncommon and should be a deliberate, discussed decision — not a default.
Botox units and Dysport units are not the same
This trips people up when comparing quotes between practices.
Dysport is a different neuromodulator with a different unit scale. The commonly used conversion is roughly 2.5 to 3 Dysport units per 1 Botox unit. So a masseter treatment of 30 Botox units per side corresponds to roughly 75-90 Dysport units per side.
A practice quoting "90 units per side" is not over-dosing you if they are using Dysport — that is a normal equivalent dose. Always confirm which product a quote refers to before comparing per-unit prices or unit counts across practices.
Both products work well in the masseter. Dysport tends to diffuse slightly more, which some injectors prefer for large muscles; Botox is more commonly used and slightly more precise in its spread.
Why a good injector starts low
On a first masseter treatment, many experienced injectors deliberately dose at the conservative end of what they estimate you need.
The reasoning is asymmetric risk. If you are under-dosed, the fix is straightforward: come back at two weeks, add units, done. If you are over-dosed, there is no reversal agent for neuromodulator — you wait it out, potentially for months.
Over-relaxation of the masseter can produce a genuinely uncomfortable few weeks: noticeable chewing fatigue with tough foods, and in some patients a sense that the bite feels different. It resolves fully, but there is no way to speed it up.
If your injector proposes starting at 25 units per side rather than the 40 you read about online, that is usually good practice rather than under-treatment.
What the two-week follow-up is for
Masseter Botox is one of the treatments where a follow-up genuinely earns its place.
At two weeks, the neuromodulator has taken full effect on muscle activity even though the visible slimming has not developed yet. Your injector can feel how much clench force remains, compare sides, and add a small number of units if one side is stronger than the other — which is extremely common, since most people chew preferentially on one side.
Asymmetry is the single most common thing corrected at follow-up. Catching it at two weeks means it never becomes visible.
Dose versus timeline: two different things
Patients often conclude their dose was too low when nothing looks different at three weeks. Almost always, the dose was fine and the timeline was misunderstood.
- Week 1-2: clenching force drops. You may notice you are not waking with a tight jaw. Nothing looks different yet.
- Week 3-6: the muscle begins to reduce from disuse. Subtle shape change starts.
- Week 6-12: visible slimming develops. This is when photos show a difference.
- Month 4-6: effect gradually wears off; muscle activity returns.
Judging your result before week eight is judging it early. The functional benefit and the cosmetic benefit arrive on completely different schedules.
Does more product mean a slimmer jaw?
Only up to the point of full muscle relaxation. Past that, additional units do nothing useful and increase the risk of unwanted spread to neighboring muscles.
The ceiling on how much your lower face can slim is set by how much of your jaw width is muscle rather than bone. If your jaw is wide because of the angle and structure of the mandible itself, masseter Botox will soften the contour but cannot change the underlying bone — and no dose will change that.
An honest injector will tell you this at consultation rather than escalating your dose session after session in pursuit of a result that is anatomically unavailable. If bone structure is the main driver, that is a conversation about different options entirely.
