Why must Botox be reconstituted using 21 gauge needle? What happens if 18 gauge or 25 gage is used?

Why must Botox be reconstituted using 21 gage needle? What happens if larger 18 gage or smaller 25 gage is used?

Doctor Answers 9

Reconstitution of Botox

When Botox was first introduced as Botox Cosmetic, the company was somewhat emphatic about how it was to be reconstituted. The training courses back in the late middle 1990's indicated that the molecules were somewhat fragile and that allowing a quick jet of saline to hit the Botox molecules could damage them. The recommendation was to use a 21 or 22 gauge needle and resist letting the plunger pull down quickly. We replaced a nurse in the clinic who didn't do it that way and we had two vials that got injected where patients had a much poorer response and had to be re-injected. I think its a difference that probably makes a difference. We also use preservative free normal saline to reconstitute.


Independence Plastic Surgeon
4.8 out of 5 stars 6 reviews

Botox Reconstitution

Dear jerronba,

Botox is reconstituted using salt water prior to injection. This can be performed using any appropriate size needle.

Injection is commonly performed using a very small needle. I prefer to use a 32 gage needle that is commonly called a nanoneedle.

Warmest wishes,
Larry Fan, MD

Larry Fan, MD
San Francisco Plastic Surgeon
4.3 out of 5 stars 15 reviews

Botox reconstitution

Thank you for your question jerronba. Botox is a purified protein used to address wrinkles associated with facial expression. It comes as a dry powder in 50 unit or 100 unit vials. The manufacturer recommends reconstituting Botox in 2.5 mL of saline for 100 units. The gauge of the needle does not matter. Larger needles (smaller numbers) will allow the saline to pass through faster than smaller needles (smaller sizes). We use 27 Ga needles to reconstitute the Botox and 30 Ga needles for injections. Many doctors use larger needles for reconstitution. Please consult with a doctor for specific recommendations. Good luck!

Alex Eshaghian, MD, PhD
Encino Physician
5.0 out of 5 stars 1 review

Botox and Reconstitution

It does not matter what size the needle used to reconstitute the Botox with.  Only what product you use to dilute the Botox.  Best, Dr. Green

Dr Knight answers questions about Botox

Hi and thanks for your question.  This is interesting - no one has ever asked me this before.  It matters not what gauge needle you use to reconstitute Botox or any other neurotoxin.  Package inserts reflect what Allergan went to the FDA with and this variable will not affect patient care.

J. Matthew Knight, MD
Orlando Dermatologic Surgeon

Why is Botox reconstituted with a 21 g needle

  • A great question because Botox does not have to be reconstituted with a 21 g needle.
  • First step - sterile saline is drawn up with whatever needle the doctor selects.
  • Second step - that sterile saline is injected into the Botox via, with whatever needle the doctor selects.
  • Third step - Botox is drawn up into a new syringe usually with a 27 g needle to avoid wasting any Botox
  • Fourth step - Botox is injected into the patient with a 29 or 30 g needle, or smaller.
  • Always see a Board Certified Plastic Surgeon.
Hope you find this information helpful. Best wishes.

Why must Botox be reconstituted using 21 gauge needle? What happens if 18 gauge or 25 gage is used?

Thank you for your excellent question.  Reconstitution of Botox involves placing a saltwater solution into the prepackaged vial of dried product, using whatever size needle that the injector wishes.   Once ready for injection a smaller gauge (typically a 29 or 30) is used to administer the Botox to patients.  This maximizes comfort and minimizes potential issues, such as bruising. 

Nelson Castillo, MD
Atlanta Plastic Surgeon
5.0 out of 5 stars 43 reviews

Botox Needles

Botox can be reconstituted with any size needle but must be large enough to draw up the solution. It's really personal preference.
A smaller needle should be used to administer the Botox for maximum comfort for the patient and without leaving the injection site noticeable. 
Thank you for your question and have a great day!

Michael K. Obeng, MD, FACS
Beverly Hills Plastic Surgeon
5.0 out of 5 stars 46 reviews

25G is used to inject Botox

You can mix with any needle.

Larger needles not used because it will scare patients ! 

18G is larger than 21 G which is larger than 25 G.

25G is too small to draw and it will bend when you push it through the soft plastic bottle top.

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.