What is a Botox Unit?

What is a unit? How many units are in a Botox bottle?

Doctor Answers 12

Botox Unit

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A Botox unit is essentially a measure of a defined amount of biological activity and corresponds to a fixed number of botulinum toxin molecules. Botox typically comes in 100 unit vials. As a patient you ought to keep track of how many units were injected in which locations.

Good luck.

San Diego Dermatologist

What is a Botox Unit

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We use Unit as a measure of Botox (think, mg of medications or ml of liquid). However, from a scientific point of view, a Unit is defined as, the dose required to be  toxic for 50% of medical mice. This is not meant to scare people, but it was the definition used by these companies and regulating bodies. Also, the injection is made in a different manner in mice and mice obviously need FAR less of the medication to be toxic. 

James Bonaparte, MD, MSc, FRCSC
Ottawa Facial Plastic Surgeon
5.0 out of 5 stars 21 reviews

Botox Units

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There are usually 50 or 100 Units in a vial. Think of Botox Units as grains of salt (or in this case gains of Botox) dissolved in water. The same number of Units can be put in 1 syringe or many syringes and the same number of Units can be dissolved in 1 ml or 10 ml of water depending on the concentration desired.

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Botox unit

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A unit is a measurement of the biological activity. Botox normally comes in a vial (bottle) of 100 units. An experienced surgeon will know how many units you need.

Cory Torgerson, MD, PhD, FRCSC
Toronto Facial Plastic Surgeon
4.7 out of 5 stars 170 reviews

Botox units

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A unit is what is used to measure an amount of Botox before it has been reconstituted. Each vial of Botox Cosmetic normally contains 100 units. 

There are 100 units in a botox vial.

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This is an arbitrary number derived from studies in animals. There are 100 units in every Botox vial.  You should ask your doctor to see the bottle (look for the authentic hologram) and ask how fresh the Botox is. Always make sure the price is by the unit, not the cc.

Charles E. Crutchfield III, MD
Minneapolis Dermatologic Surgeon

How is a Botox unit is measured & why authentic Botox is important

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Standard dosing ranges of Botox units to treat certain regions of the face have been published in the medical literature. The measurement of the Botox unit is done in the the manufacturer's (Allergan) lab on each batch of Botox; a unit measures the biologic activity of the Botox so the strength can be kept within a narrow, uniform range.

That is why the FDA recommends that practitioners use Botox Cosmetic purchased from Allergan within the USA. The bottle comes with a hologram for verification of the authenticity of production.

Edward Szachowicz, MD, PhD
Minneapolis Facial Plastic Surgeon
4.6 out of 5 stars 14 reviews

A Unit of BOTOX is a measure of biological effect

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Dear Aglaet

One unit of BOTOX refers to the biological activity of this medication which is a neuromuscular toxin. The toxin is taken up at the terminus of of the nerve that is responsible for stimulating muscle contraction. The effect of the toxin is the prevention of acetylcholine release at the nerve terminus, preventing muscle contraction. The effect of BOTOX is temporary because the nerve eventually replaces the block terminus.

The definition of a unit the amount of BOTOX that when injected into a 18-20 gram Swiss-Webster female mouse is lethal for 50% of the animals. Currently each lot of BOTOX is tested in this fashion to assure the safety of the product. Animal advocates have challenged Allergan, the maker of BOTOX, to use an assay for the product that does not involve animals dying from respiratory arrest. There is a leg paralysis test that could be used. The difficulty is that as you can imagine, the testing of BOTOX is what ensures the safety of BOTOX. The track record of this product is impeccable. The FDA has approved and vetted the safety of BOTOX based on this testing method. Therefore, changing the testing of the drug would require the approval of the FDA and this is improbable.

Now although one unit of Botox is obviously very dangerous if you are an 18 gram mouse, the amount of BOTOX used for a cosmetic service does not appear to associated with systemic side effect. On the other hand, the FDA is now requiring a new warning for the use of Dysport and BOTOX that these treatments in high enough dose can be assoicated with systemic side effects. The systemic side effects appear to only be associated with the very high doses used to treat medical conditions like cervical dystonia and muscle spasm seen in children with cerebral palsy.

Allergan packages BOTOX in the United States market with 100 units of BOTOX. Dysport is now approved for the United States market. It is also a botulinum toxin A. However it is packaged in vials of 300 and 500 units in the United States. These two drugs are not equivalent. While some claim that BOTOX is approximately 3 times stronger than Dysport, this formula is not precise and it takes clinical experience to determine what is the correct dosage for a give person with any of these products.

Kenneth D. Steinsapir, MD
Beverly Hills Oculoplastic Surgeon
4.9 out of 5 stars 26 reviews

BOTOX has 100 units per vial

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Botox has 100 units per vial. The effectiveness of the Botox on diminishing muscle movement is dependent on the dose of units given, not the dilution. Doctors must dilute the bottle of Botox powder with saline to make it a liquid. The doctor then knows, based on the amount of liquid added to the bottle, how many units are contained in a given volume of liquid.

Ronald Shelton, MD
Manhattan Dermatologic Surgeon
4.9 out of 5 stars 39 reviews

Botox Unit???

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It is the measurement scale and is standardized for Botox made by Allergan.

One bottle has 100 units. Typically we use 20units in the area between eyebrows called Glabella.

Remember the units are different for Dysport the newly approved Botulinum toxin launched by the company Medicis. Their bottle has 300units and typically we inject 50units in the Glabella.


Tanveer Janjua, MD
Bedminster Facial Plastic Surgeon
5.0 out of 5 stars 126 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.