How many units of Botox do I need at 23 years of age for my 11 lines (glabella) in my forehead?

Thank you for sharing your excellent question.  The best advice is with an in-person examination to assess your glabellar muscle strength but in general patients require anywhere from 12-25 units.  Smaller doses may work but can lead to a shortened duration of action.  Hope this helps.

Hello and thank you for your question. You can always start on the lower end of the unit spectrum and add more if needed. I would recommend doing an in person consultation with a dermatologist to find out exactly what is recommended for you. 

Thank you for your question Petite Girl. I understand your concern. Botox is a purified protein
used to address wrinkles associated with facial expression. When injected into
the skin Botox will relax the muscles and smoothen out the overlying wrinkles. The
most common areas of treatment are in the upper face. These include the
horizontal lines seen on the upper forehead when one raises the brows, the
vertical lines seen between the brows when one frowns (frown lines), and the
crow's feet seen around the eyes when one smiles. It is difficult to make an assessment without a
formal exam in the office where I can view the skin in multiple angles and observe
wrinkles formed with facial expression. However, I hope the information
provided here is useful.The appearance of frown lines is variable from
person to person. Usually they are in a vertical orientation but sometimes they
can be oblique and sometimes a horizontal line is seen across the upper portion
of the nasal bridge. The most common variation is to have two parallel lines,
hence the common term "11's" to describe them. But some people have
one, three, or more lines. Some people also will see a bulge in the area when
contracting the muscle. This bulge is smoothened out after a Botox treatment.The pivotal studies used 20 units of Botox in
the glabella area between the brow to address the frown lines. These studies
demonstrated that the peak results are seen 14 days after the treatment and
most people enjoy their results for 3-4 months. At that point, a maintenance
treatment is recommended. While some people start to see results as early as
the next day, it can take two weeks for full results so patience is
important. We have our patients return two weeks after their treatment to
assess their results via photographs. At that time additional units may be
added if necessary. Although 20 units is a good standard dose to
start with, some people require a higher dose because of higher muscle volume. This
is common in mature patients, in those with large bulges from expressive faces,
and in men. I find that Botox still works in these cases, just a higher dose is
required. I have used up to 40 units in the glabella.I have some patients that prefer to receive a lower dose than recommended. In these cases I have found that full results may not be seen and patients do not enjoy their results for the full three to four months.With any injection, there are risks such as
pain, bleeding, bruising, redness, swelling, tenderness, and infection. We take
special precautions to minimize these risks such as using a painless technique.
We also treat bruises with a laser as early as the next day. Bruises usually
resolve within two weeks if untreated. After a laser treatment bruises usually
resolve in 1-3 days, but may still take two weeks for full resolution. In
addition to these risks, with Botox there is also a risk that the product
spreads or diffuses to nearby structures. Spread to nearby muscles
can lead to side effects such as the temporary appearance of droopy eyelids or
a temporary asymmetric smile.After a Botox treatment, I recommend that my
patients avoid heat exposure, alcohol consumption, and strenuous exercise for
24 hours and not lie down flat for four hours. This is because all of these
activities may possibly lead to the movement of the product and consequent side
effects such as droopy eyelids as described above. Although there have been no
definitive studies shown that these actually occur and some physicians do not
provide such aftercare instructions, in the absence of data I err on the side
of caution and recommend that my patients avoid such activities.Please consult with a doctor for specific
recommendations. Good luck!

The studies on Botox in the glabella were done with 20 units. However, for many younger women, I find 12 units works well. There is nothing wrong  with starting at a lower amount (4 units per side) and adding more 2 weeks later if needed. 

No 2 people are alike and it is very difficult to predict exactly how much Botox you will require. You can always start with little and increase only if necessary. An in-person evaluation is kind of mandatory. Good luck from New York City

There is no way to predict Botox effect, particularly for the first time. Do not pay attention to the number of units published online. The "recommended" are not recommended because that dosage will give you the best aesthetic results. Start low 5-6 units per side. The price depends on your area. Nobody is able to tell you that 4 units will have no effect. Remember, there is zero advantage to have these muscle "frozen".It doesn't make those lines go aways faster. Also, there are certain external conditions that may make those lines worse and elimination of those will have great effect. for example, deteriorating eyesight, looking at the computer screen for hours every day, working in relatively dark environment, continuous use of smartphone, texting etc. All these, and many others, almost always force you to frown to certain degree without you being aware of it. Good luck!

The standard dose for the glabellar complex is 20 units and if you get less to save money it will either not work well or not last. see a board certified dermatologist

The dose depends of the forehead size, the strength of the muscle too . So I can say that the 10 u will help to stimulate,  but only the professional in the moment can tell the proper dose in your case.
 

To be honest it is difficult to answer this questions without having you directly in front of me. The units used depends entirely on the size and strength of the muscle. Whoever treats you will be able to provide you with the correct amount.
Having botox this early will enable you to forget how to frown, so in the future you should need less botox, less often. The lines should fill themselves in. Whatever you pay now you will save in the future.