Ask a doctor

How Long Does Botox Take to Work in the Masseter Muscles?

How long does Botox take to work in the masseter muscles? I have thick masseter muscles and i want to get some botox injections on each side to reduce them, can anyone possibly tell me about how long after the injections will they really shrink down? i have heard that it takes months to work from some people and then from others it just takes days, thanks for the answers.

Doctor Answers 14

Botox for masseter muscle

Botox begins working in 3-5 days with maximal effect towards 2 weeks and duration of effect around 4 months. For the masseters, a very strong muscle group, the effects will take likely 6-12 months to see them shrink down.

Toronto Dermatologic Surgeon
5.0 out of 5 stars 26 reviews

Have a question? Ask a doctor

Masseter muscle reduction - timing, effectiveness and onset of action

Botox works well for masseter muscle reduction and starts to work immediately - BUT muscle bulk reduction will take 4-6 months and also will require at least 2-3 sessions of treatment. It is expensive because it requires a large # of units of Botox.

Botox Effect on Masseter Muscles

Botox usually takes 2 or 3 days to start to work, and will continue to improve over the first 7 to 10 days. The improvement will last up to 6 months. Once the effect starts to wear off, you will need a repeat treatment to maintain your result. Some find that the effects last longer after having multiple treatments, even up to a year.

Masseter Reduction with Botox

   Masseter reduction occurs over months to years, although the Botox begins to work in several days to a week.

Botox in the Masseter Muscles

You should see a slight improvement in the masseter muscle area a few days after Botox injections.  For the full effect, it could take a few months due to the size of the muscle.  I recommend keeping up with injections every 4 months to maintain the slimming appearance.   This is a wonderful treatment option for patients who are looking for a non-surgical approach to improve the appearance of their cheeks and jaw.  I hope this helps. 

Paul L. Leong, MD, FACS
Pittsburgh Facial Plastic Surgeon
5.0 out of 5 stars 32 reviews

Botox to masseter muscles

Botox can take from a few days to two weeks to start working. For masseter reduction, it is dependent upon number of units you were treated with and what sort of expectations you have and discussed with your provider. It can take several months, and you need to continue treatment to maintain the reduction.

Sam Naficy, MD
Seattle Facial Plastic Surgeon
5.0 out of 5 stars 153 reviews

Botox for the masseters

It can take several months to see the full effect of Botox injections on the masseter muscles.  You may require a second treatment at that time and then the effect may last a year or longer.

Martie Gidon, MD, FRCPC
Toronto Dermatologist
5.0 out of 5 stars 18 reviews

Generally changes after a month

The Botox will take effect within 2 weeks after injection. Once the masseter muscle has completely relaxed, the reduction of the muscle will occur over the following 2-4 weeks. Most patients notice changes at the 1-2 month follow up.


Repeat treatments help to maintain results and prolong duration of effect.

David W. Kim, MD
Bay Area Facial Plastic Surgeon
5.0 out of 5 stars 24 reviews

Botox for masseter reduction

You will notice a reduction in muscle activity at ~3 days after the injection, and will see maximal effects at ~7 days after injection.  Depending on the dosage administered, you may have residual masseter activity even when the Botox or Dysport is fully active.  Especially in patients with very large masseters, it may take a two or more treatments with Botox or Dysport to achieve the maximal result.  Re-treatment at 1 month after the initial injection works well to reduce residual activity.

Long-term muscle atrophy and size reduction will be noted after serial treatments with Botox/Dysport.  The initial loss in size will simply come as a result of the muscle's inability to contract.  

Donald B. Yoo, MD
Beverly Hills Facial Plastic Surgeon
5.0 out of 5 stars 21 reviews

Botox works for Masseter hypertrophy of the jaw

It takes 1 week for Botox to work. The peak effect is seen at 30 days. We usually see improvement in treating the Masseter after the second session, which is 3 months following the initial treatment.- Dr. Gross

Edward J. Gross, MD
Orlando Facial Plastic Surgeon
4.0 out of 5 stars 9 reviews

These answers are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.