Botox reconstitution: units per mL and per 0.1 mL
Reconstitution means adding saline to a freeze-dried vial. How much you add decides how many units end up in each millilitre.
The formula
Units per mL = units in the vial divided by millilitres of saline added. Units per 0.1 mL is that number divided by 10.
Worked example
A 100 U vial with 2.5 mL of saline gives 100 / 2.5 = 40 U per mL, which is 4 U per 0.1 mL. A 20 U dose is then 20 / 40 = 0.5 mL.
Common dilutions
| Vial | Saline | U per mL | U per 0.1 mL |
|---|---|---|---|
| 100 U | 1 mL | 100 | 10 |
| 100 U | 2 mL | 50 | 5 |
| 100 U | 2.5 mL | 40 | 4 |
| 100 U | 4 mL | 25 | 2.5 |
| 50 U | 1 mL | 50 | 5 |
| 50 U | 2 mL | 25 | 2.5 |
This is arithmetic, not a dosing recommendation. Follow the product label, your protocol and your clinical judgement.
Why record the dilution
If two injectors in one clinic use different dilutions, the same number of marks on a syringe means different doses. Record the dilution with the session so the next provider knows what was used.
Use our free reconstitution calculator to check your numbers.
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