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 17

When does Botox start to work.

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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.

Botox in the Masseter Muscles

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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
4.8 out of 5 stars 50 reviews

Botox for masseter muscles

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Botox can be used effectively to treat large masseter muscles.  Once injected, it will only take a matter of days to a week for the Botox to begin working.  After this time, you should notice that the masseter muscle does not clench up as much as before the treatment.  It can take a matter of months to see further reduction in the size of the muscle however.  Like any muscle, once it is not exercised, it will reduce in size over a period of months. 

Michael I. Echavez, MD
San Francisco Facial Plastic Surgeon
4.5 out of 5 stars 18 reviews

It can take up to 3 months to see the final cosmetic results of masseter muscle Botox

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Yes. Clenching teeth, or "grinding you teeth" can cause the masseter muscle to get bigger, or "hypertrophy". The masseter muscle is one of the muscles activated during chewing. It’s located at the “angle of the mandible”, or “angle of the jaw”. Masseter muscle hypertrophy is enlargement of the masseter muscle, and can contribute to a harsh, square look at the angle of the jaw. Botox can be used to relax this muscle, and to soften the look of the lower face. I usually start with 50 units of botox (25 units on each side). When Botox is used to relax the facial muscles that cause fine line, the maximum effect is seen in 7-10 days. When Botox is used to reduce masseter muscle hypertrophy, the maximum effect is not seen for 3 months. Results can last up to 9 months. I recommend repeat injection every 6 months if you would like to maintain your results. 

Dara Liotta, MD
New York Facial Plastic Surgeon
4.9 out of 5 stars 31 reviews

Botox in Masseter Muscle

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Botox is a great way to reduce the Masseter muscle and slim the face. It generally takes 2 weeks or more for the muscle to shrink.  There are times when it can take several weeks or subsequent injections over time to decrease the size of the muscle.  It can take several weeks for the muscle to decrease and notice the facial slimming and sometimes a second course of Botox is needed. Best, Dr. Green

Botox Effect on Masseter Muscles

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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.

Botox to masseter muscles

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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, FACS
Seattle Facial Plastic Surgeon
4.7 out of 5 stars 231 reviews

Botox for the masseters

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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

Generally changes after a month

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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
4.8 out of 5 stars 39 reviews

Botox for masseter reduction

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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
4.9 out of 5 stars 64 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.