just wondering if 9 units of botox will be enough to notice a difference?

Generally, when I see a patient for the first time I like to be conservative in the amount I use. Remember, you can always add more, but you cannot reverse giving too much. That said, 9 units is extremely conservative for achieving a desired result. Every patient should be treated as an individual. some may need more than others. The amount given not only involves the required result, but can have an impact on how long the results last.

As others have stated 12 to 20 units is the usual dose in that area but 9 units will soften the lines and the effect will not last the usual 12 weeks.