Most questions about forehead dosing have no official answer, because the forehead is off-label for most botulinum toxin products. Xeomin is one of two exceptions — Botox Cosmetic is the other — so this one has a real number behind it.
20 units, in five equal injections of 4 units, into the frontalis — the flat sheet of muscle across your forehead that lifts your brows.
The label adds a placement rule: injections should be at least 2 cm above the bony rim of the eye socket. That distance is the safety margin for your brow position.
The label directs that the forehead be treated in conjunction with the frown lines, and it says why: to reduce the chance of the brows dropping.
Your forehead muscle is the only one that lifts your brows. The muscles between your brows pull them down. Relax the lifter on its own and the downward pull is unopposed, which can leave the brow sitting lower than before. Treating both keeps the two forces in balance.
So a realistic forehead appointment is 40 units: 20 in the forehead, 20 in the frown lines.
If you are also treating the lines at the outer corners of the eyes, the label dose is 24 units — 4 units at three points on each side.
Everything together — frown lines, forehead, crow's feet — is capped at 64 units in a single session.
It is tempting to think a stronger forehead needs a bigger dose. The label does not offer one, and there is a good reason to be careful rather than generous here.
Over-treating the frontalis is what produces heavy brows and hooded lids. That is usually a cosmetic problem rather than a medical one, it lasts for months, and there is nothing to be done except wait — but if the heaviness is enough to get in the way of your vision, or if an upper eyelid itself is drooping, that should be looked at rather than waited out. Injectors generally prefer to start at the approved dose, review at two weeks, and add units if the result is lighter than you wanted.
Adding is easy. Removing is impossible.
If you have had Dysport or Botox in your forehead, do not carry the unit number across. Every one of these labels states that its units cannot be converted into another brand's.
20 units of Xeomin in the forehead is not a smaller treatment than 50 units of Dysport somewhere else. They are different scales.
Go to an emergency department or call 911. Do not wait for a call back. These are rare, but they are the symptoms named in the FDA boxed warning that every botulinum toxin product carries, deaths have been reported, and they can begin hours or even weeks after treatment.
If a vision change is sudden or severe, seek urgent care rather than waiting.