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

9 units of Botox is about half the normal dose for that area. I have many patients that do low doses of Botox. They understand that it will not last as long but like to have some movement of the muscles. Given your age this sounds appropriate. 

9 Units of Botox is not a lot at all. It may work for you and it may not. It will take you around 7 days to notice the full effect. If you still have motion of your Glabella muscle, which you will, you may need more to knock it out completely.

While 20 units is the average dose used between the brows in the glabella region, this may vary from patient to patient. Hopefully your injecting physician took before photos for comparison and of course you can judge your results too. A lower dose should help to soften the area at least, but it really depends on how severe things were at the start. Lower doses also don't tend to last for the average 3-4 months of duration. As always be sure you see a core board certified physician for cosmetic injections (facial plastic surgeon, plastic surgeon, or dermatologist). 

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.

Thank you for your question. 9 units of Botox is pretty conservative, but each patient has a range that will be effective for their liking. Usually 20 units of Botox is recommended for a full affect, but 9 units may be enough for what you are seeking. Be sure to followup with your injector if a touch up or more correction is needed.Sincerely,Benjamin J. Cousins MDBoard Certified Plastic Surgeon

The usual dose can range from 12-20 units.  The 9 units would be considered a conservative amount.  The results would be less long lasting but the results should still be visible.

Hello & thank you for your question!
For your age & treatment area, this sounds to be accurate enough but please follow up with your practitioner for a review appointment.
Best wishes,
Mr Golchin

Nine units for the Glabella (frown lines, "elevens") area is very conservative.  On average most women need about 20 units, and men about 26 units in that area, if not more. The glabellar complex encompasses a strong group of muscles between the eyebrows that are constantly being utilized (eg. frowning, thinking, working on your computer, dreaming, squinting in the sun) and therefore, 9 units generally is not sufficient to treat this area. This underdose can either result in the treatment not effectively treating the area or not lasting the average 3-4 months.  With this said, I think it's great that you are practicing prevention, and you can certainly return to your provider in 7-10  to add more if the initial treatment was not sufficient.  

9 units is very conservative. Which makes sense given your age. My best advice is to wait a couple of weeks and see if you like the results. If not then you'll know to go with a higher dosage next time. Best of luck.