Frown lines — the vertical “11s” between the brows — are produced by the glabellar complex: the paired corrugator supercilii muscles and the procerus, which together pull the brows inward and downward. Treating them with Botox® is one of the most predictable procedures in aesthetic medicine, and the reason is simple: the glabella is the only facial area where the injection map, the dose and the depth are all spelled out in the FDA label. Everything else you do well here comes from the facial anatomy underneath each injection site.
This guide sets out exactly where to inject, how many units to place at each point, how deep to go, and which margins keep the toxin away from the eyelid. It has been updated for 2026 with the current Botox® Cosmetic prescribing information, new cadaveric mapping of the corrugator and its neurovascular neighbours, and the recent evidence on whether the standard five-point map should ever be varied.
It is written for injectors, but the consumer section near the end tells patients what a well-run frown line appointment should look like.
Aesthetic impact: softening the “11s” refreshes the upper face and removes the tired or stern resting expression that patients most often describe when they book.
Functional balance: the corrugator and procerus are brow depressors. Relaxing them appropriately allows the frontalis to act unopposed at the medial brow, which produces a subtle medial lift without treating the forehead at all.
Predictability: the glabella is the most reproducible area in facial aesthetics because the target muscles are large, superficial enough to palpate on animation, and covered by a labelled dosing algorithm with two decades of trial data behind it.
Procerus: a vertical muscle running over the nasal bridge from the nasal bone up into the glabellar skin. It produces the horizontal crease at the root of the nose and pulls the medial brow down.
Corrugator supercilii: paired muscles originating deep at the medial supraorbital rim and running superolaterally to insert into the mid-brow dermis. They draw the brows medially and are responsible for the vertical “11” lines. Cadaveric measurement puts mean corrugator length at 30.5 mm in women and 28.9 mm in men, with the medial origin roughly 5 mm from the midline.
Depressor supercilii: a small medial brow depressor sitting close to the corrugator origin. It is usually covered by the medial corrugator injection rather than targeted separately — there is still no outcome evidence for dosing it as an independent target.
Nerves and vessels — the part most guides skip: recent cadaveric work mapped the supratrochlear artery crossing the inferior border of the corrugator approximately 15 mm from the midline, which is essentially where the classic medial corrugator injection lands. The same study found the supratrochlear nerve has complex branching — more than three branches — in 48% of specimens and pierces the corrugator itself in 13.6%. That is the anatomical reason bruising clusters medially and why small volumes, a fine needle and brief post-injection pressure matter here more than anywhere else in the upper face. For the broader map, see our guide to nerve locations for Botox® injections.
One more anatomical fact worth holding onto: in a 2024 microdissection series, the lower corrugator fibres extended into the upper orbital orbicularis oculi in 59.5% of specimens. There is no clean corrugator “compartment” in most faces — some spread into orbicularis is built into the anatomy rather than caused by the injector.
Total dose: 20 Units of Botox®, divided as follows.
Location: the centre of the glabella, at or just above the bony nasal root, where a horizontal crease appears on frown.
Depth: intramuscular, needle perpendicular to the skin.
Medial point: above the medial brow where the muscle belly bulges on maximal frown. Depth: deep, down to bone or periosteum, then withdraw slightly before injecting — the corrugator origin is deep.
Lateral point: along the corrugator as it travels superolaterally toward the mid-brow. Keep it at least 1 cm above the bony supraorbital ridge and medial to the mid-pupillary line. Depth: more superficial — intramuscular to subdermal — because the corrugator thins and inserts into dermis as it runs laterally.
Mirror the right side, adjusting for any pre-existing asymmetry you documented at consultation.
The ptosis-reduction instructions in the Botox® Cosmetic prescribing information are more specific than the “stay 1 cm above the rim” shorthand most guides use. There are four: avoid injection near the levator palpebrae superioris, particularly in patients with larger brow depressor complexes; place lateral corrugator injections at least 1 cm above the bony supraorbital ridge; keep the injected volume and dose accurate and, where feasible, minimal; and do not inject closer than 1 cm above the central eyebrow.
For more than a decade injectors have been taught to classify patients into one of five glabellar contraction patterns — U, V, converging arrows, omega and inverted omega — and vary the injection plan accordingly. Three separate 2024–2026 studies now challenge that.
A 2026 prospective study across five centres treated 119 patients with the same standardized five-point algorithm regardless of their pattern. Wrinkle severity improved significantly at day 15 and partially regressed by day 90, exactly as expected — but there was no significant difference in outcome between any of the five pattern groups at any timepoint. On multivariate analysis, age and BMI predicted the result. Pattern did not.
An MRI study of 34 healthy adults explains why. It measured procerus, corrugator, orbicularis oculi and frontalis length, thickness, width and surface area, and found no significant difference in any muscle parameter across the five patterns. The wrinkle pattern on the surface does not correspond to different muscle anatomy underneath. Sex was the dominant variable.
A separate 2026 study of 444 patients compared a three-point technique against the five-point technique head to head and found significantly higher long-term efficacy with five points, at similar complication rates.
The practical read: the labelled five-point map is not a compromise you graduate out of — it is the best-evidenced approach for the standard case, and reducing to three points costs duration. One dissenting 2026 study using 3D dynamic strain in 142 women did find that omega and inverted-omega patients lost effect sooner by day 180, so contraction pattern may be worth recording for retreatment timing, not for changing where the needle goes.
Always mark with movement. Have the patient frown maximally so you are marking true muscle bellies rather than the resting crease. Palpate the corrugator between finger and thumb as it contracts.
Respect the margins. The label's four rules above exist because toxin reaching the levator palpebrae superioris is what causes eyelid ptosis. Mark, then check your marks against the supraorbital ridge before you draw up.
Stay medial. A 2025 cadaveric topography study found the corrugator almost overlaps the eyebrow at its medial end, sits just above the upper brow margin centrally, and has minimal muscle lateral to the mid-pupillary line — a line roughly 30 mm from the midline. Injecting lateral to it largely misses the corrugator while moving you into the territory where brow and lid problems begin.
Match depth to the muscle, not to a rule. Deep at the medial corrugator, superficial at the lateral corrugator, intramuscular at the procerus. High-frequency ultrasound of 127 participants found side-to-side asymmetry coefficients reaching 40% for both muscle thickness and depth within the same face — a good argument for palpating and adjusting rather than injecting to a fixed depth on both sides.
Keep aliquots small. Small volumes per point reduce both spread and bruising. See the section on volume below — it matters more than most injectors assume.
First-time, average female anatomy: 16–20 U total; 20 U across five points is the labelled standard. Consider 16–18 U if the brows are heavy or the lids are borderline.
Male or strong musculature: 20–24 U total. Keep the same five-point map and up-dose evenly rather than adding points.
Very fine lines or petite anatomy: 12–16 U with careful placement, and plan a two-week review for a small top-up.
Static, etched-in lines: standard dosing plus skin therapies. Toxin softens the dynamic component; it cannot erase a crease already set into the dermis, and adding more toxin does not change that. Be straight with patients about it at consultation rather than at the two-week review.
Only 20 Units across the five labelled sites is on-label. Dose tailoring by sex, muscle mass or line severity — including everything in the list above — is off-label practice. It is common, defensible and well supported by the literature, but it belongs in your consent discussion and your notes.
Injectors are taught to think in units. Recent modelling suggests the volume carrying those units is at least as important — and that the common instinct to dilute more works against you.
A 2025 multiscale diffusion model of the glabella found that raising the per-site volume from 0.025 mL to 0.1 mL produced a 2.2-fold increase in off-target exposure and a 36–49% increase in off-target effect, while receptor saturation at the intended target fell from 78% to 56%. The modelled optimum for onabotulinumtoxinA was 0.025–0.035 mL per site. Think of it like watering a single plant: the same amount of fertiliser in a small cup lands where you aimed, while the same amount in a bucket runs across the whole bed.
This is simulation, not a clinical trial, and should be treated that way. The nearest real-world corroboration comes from a 2024 randomized study of 154 patients in which a higher-concentration, half-volume protocol (0.05 mL per site) produced a median duration of 183 days, against 148–149 days for standard-volume arms. Worth knowing; not yet worth rewriting your protocol over.
Eyelid ptosis is the characteristic complication of this area. In the glabellar pivotal trials it occurred in 3% of treated patients (13 of 405) versus 0% on placebo — the only eye adverse reaction reported in the glabellar table. Real-world published figures separate sharply by injector experience.
Eyelid ptosis after glabellar injection
Bars scaled to a 6% axis. Trial figure from the Botox® Cosmetic prescribing information; real-world ranges from a 2025 review of iatrogenic blepharoptosis. Onset is typically 3–14 days after injection, with spontaneous resolution over roughly three months.
Managing it when it happens. Oxymetazoline 0.1% ophthalmic solution has randomized-trial support for improving margin-reflex distance and visual field, and apraclonidine is used similarly off-label. Beyond drops, reported options — exercises, and targeted pretarsal toxin — rest on very small case series. Our full guide to droopy eyelid after Botox® covers assessment and the treatment ladder in detail.
Asymmetry: map and dose evenly, and correct pre-existing asymmetry with small adjustments rather than large ones. Remember the 40% within-face depth asymmetry finding above — symmetric marks do not guarantee symmetric depth.
Headache and brow tightness: usually transient. Small aliquots and even distribution help. Note that the frequently quoted 9% headache rate comes from the forehead lines trials at 40 Units, not from the glabellar data — do not quote it for a glabella-only treatment.
Bruising: minimise passes, use a fine needle, and apply brief pressure — particularly medially, where the supratrochlear vessels sit.
All botulinum toxin products carry a boxed warning for distant spread of toxin effect: postmarketing reports describe symptoms consistent with botulinum toxin effect — asthenia, generalised muscle weakness, diplopia, ptosis, dysphagia, dysphonia, dysarthria, urinary incontinence and breathing difficulty — occurring hours to weeks after injection, with swallowing and breathing difficulties capable of being life-threatening.
The context patients deserve alongside it: the label itself states that no definitive serious adverse event reports of distant spread have been reported at the labelled 20-Unit glabellar dose. The warning is real and belongs in your consent; the risk profile at aesthetic doses in this area is not the same as at therapeutic spasticity doses.
For the wider map of higher-risk facial territory, see our reference on Botox® danger zones.
Balanced upper face: treating the forehead alone risks brow heaviness, because you have weakened the brow elevator while leaving the depressors intact. Treating the glabella alone often produces a subtle medial lift and frequently stands on its own.
Common combined plan: 20 U in the glabella plus conservative frontalis dosing placed high, to soften horizontal lines while preserving brow position. Our forehead unit dosing guide covers the frontalis side in detail.
One finding worth counselling on: a 2025 randomized trial measuring 3D facial strain found that as glabellar strain decreased after treatment, lateral canthal strain increased — patients recruit the muscles you did not treat. Telling someone in advance that their crow's feet may look slightly more active is far better than having them discover it at the two-week review.
Onset: the label states that chemical denervation begins one to two days after injection and increases in intensity through the first week. In the pivotal trials, 74% of patients were already rated none-or-mild at day 7 and 80% at day 30.
Duration: approximately three to four months. The trial curve is useful for setting expectations honestly: 70% none-or-mild at day 60, 48% at day 90, and 25% at day 120. Do not retreat more frequently than every three months.
Immediate aftercare — what the evidence actually supports: avoid rubbing or massaging the treated area, and stay upright and normally active for the rest of the appointment. The familiar “don't lie down for four hours” rule does not appear anywhere in the FDA label, and a 2025 study of more than 5,000 treatments using a ten-minute upright protocol reported no cases of ptosis. What does plausibly move toxin is anything that causes swelling or firm pressure over the injected area in the days afterwards — so the more useful instructions are to skip facials, laser, peels and microneedling for about two weeks, and to avoid strenuous exercise for 24 hours (see exercising after Botox®).
Two-week review: reassess at maximal frown and adjust with small add-ons — typically 1–2 U into the most active point. Do not add toxin if any heaviness is present; let it partially wear off and reassess.
Glabellar lines is the one indication every US-approved botulinum toxin shares. If you trained on Botox® alone, this is the table to internalise before a clinic switches product on you. Letybo®, the newest, was approved on 29 February 2024 and launched in the US in March 2025.
| Product | Glabellar approval | Total dose | Per site | Duration in label |
|---|---|---|---|---|
| Botox® Cosmetic | Apr 2002 | 20 U | 4 U / 0.1 mL | ~3–4 months |
| Dysport® | Apr 2009 | 50 U | 10 U | Up to 4 months |
| Xeomin® | Jul 2011 | 20 U | 4 U | 12–16 weeks |
| Jeuveau® | Feb 2019 | 20 U | 4 U / 0.1 mL | Not stated |
| Daxxify® | Sep 2022 | 40 U | 8 U / 0.1 mL | Not stated |
| Letybo® | Feb 2024 | 20 U | 4 U / 0.1 mL | Not stated |
All six use a five-site pattern into the two corrugators and the procerus. Units of biological activity are not interconvertible between products.
Two things in that table are worth pausing on. First, three of the six labels — Jeuveau®, Daxxify® and Letybo® — contain no duration-of-effect statement at all. The widely repeated “six months” figure for Daxxify® is a trial-narrative and marketing claim, not label language; the only interval statement in that label is the standard “no more frequently than every three months.” Second, the ptosis-margin wording differs product to product: Botox® Cosmetic, Jeuveau® and Letybo® specify the lateral corrugator injections, Dysport® specifies the medial ones, and Xeomin® says simply “corrugator.” Read the label of the product in your fridge. Our comparison of Xeomin® and Botox® goes further into how the products differ in formulation.
Heavy medial brows or mild dermatochalasis: favour the procerus and medial corrugator points, keep totals conservative, and avoid low placement entirely.
Short forehead or low brow position: be extra cautious if you are also treating the frontalis. The glabellar map stays standard; keep the corrugator points high.
Prior eyelid surgery or a history of ptosis: document carefully, dose conservatively, and hold your margins strictly. Photograph before you inject.
Patients also receiving therapeutic toxin for migraine, dystonia or spasticity: cumulative dose and treatment frequency are the modifiable drivers of neutralizing antibody development. Coordinate rather than treating your aesthetic dose in isolation.
This distinction gets blurred constantly, and it matters for both consent and patient counselling. The Botox® Cosmetic label — like every other US botulinum toxin label — lists exactly two contraindications.
| Status | Situation | What the label says |
|---|---|---|
| Contraindication | Known hypersensitivity to any botulinum toxin preparation or formulation component | Section 4.1 — absolute |
| Contraindication | Infection at the proposed injection site | Section 4.2 — absolute |
| Caution | Pregnancy | Section 8.1 risk summary: no adequate human data; adverse fetal effects in animal studies at clinically relevant doses |
| Caution | Breastfeeding | Section 8.2 risk summary: no data on presence in human milk; weigh benefits against clinical need |
| Caution | Neuromuscular junction disorders (myasthenia gravis, Lambert–Eaton) | Warning — these patients may be at increased risk of clinically significant effects |
| Caution | Aminoglycosides and other agents that may potentiate neuromuscular effect | Drug interactions section — weigh risks and benefits |
None of this means you should treat a pregnant patient. Elective aesthetic treatment in pregnancy is almost always deferred, and that is the right call. But deferring for sound clinical judgement is different from telling a patient the product is contraindicated, which is not what the label says — and patients increasingly check.
If you are researching this as a patient rather than an injector, here is the short version — our plain-language guide to Botox® for 11 lines covers it in more depth.
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The FDA-approved dose is 20 Units total, delivered as five injections of 4 Units each — one into the procerus and two into each corrugator supercilii. That exact 5-site, 20-Unit pattern is what the Botox® Cosmetic label specifies and what the pivotal trials studied. In practice most patients do well between 16 and 24 Units depending on muscle strength, sex and line severity, but anything outside 20 Units across five sites is off-label dosing.
One point in the procerus at the midline over the nasal root, and two points per side in the corrugator supercilii — a medial point near the medial brow where the muscle belly bulges on frown, and a more lateral point along the muscle as it travels superolaterally. Keep the lateral corrugator points at least 1 cm above the bony supraorbital ridge, never inject closer than 1 cm above the central eyebrow, and stay medial to the mid-pupillary line: cadaveric mapping shows there is minimal corrugator muscle lateral to that line.
Ptosis comes from toxin reaching the levator palpebrae superioris, which happens when injections are placed too low, too lateral, or in too large a volume. The label's rules here are: avoid injecting near the levator, place lateral corrugator injections at least 1 cm above the bony supraorbital ridge, and keep the injected volume and dose accurate and minimal. Eyelid ptosis occurred in 3% of patients in the glabellar pivotal trials. Real-world published rates run roughly 2.5 to 5.4 percent among inexperienced injectors versus about 0.5 to 1 percent among experienced ones, which makes technique training the single biggest variable.
The Botox® Cosmetic label states that chemical denervation of the injected muscles begins one to two days after injection and increases in intensity during the first week. In the pivotal trials 74 percent of treated patients were already rated none-or-mild at day 7 and 80 percent at day 30. Duration of effect for glabellar lines is approximately three to four months, with 48 percent still none-or-mild at day 90 and 25 percent at day 120. Do not retreat more frequently than every three months.
No. The Botox® Cosmetic label lists exactly two contraindications: known hypersensitivity to any botulinum toxin preparation or formulation component, and infection at the proposed injection site. Pregnancy and lactation appear in Section 8 as risk summaries stating there are no adequate human data, and pre-existing neuromuscular disorders appear as a warning, not a contraindication. These are real reasons for caution and documented shared decision-making, but calling them contraindications misstates the label.
Current evidence says the standard map holds up. A 2026 five-centre prospective study of 119 patients treated every glabellar contraction pattern with the same standardized 5-point algorithm and found no difference in wrinkle severity or aesthetic improvement between any pattern at any timepoint. An MRI study of 34 adults found no significant difference in glabellar muscle length, thickness, width or surface area across the five patterns. Age and BMI predicted outcome; pattern did not. One 2026 study using 3D strain measurement did suggest omega and inverted-omega patterns relapse sooner by day 180, so pattern may be worth tracking for retreatment timing rather than for injection placement.
Glabellar lines is the one indication all six US-approved botulinum toxins share: Botox® Cosmetic, Dysport®, Xeomin®, Jeuveau®, Daxxify® and Letybo®, the newest, approved February 29 2024 and launched in the US in March 2025. All six use a five-site pattern, but the total doses are not the same — 20 Units for Botox® Cosmetic, Xeomin®, Jeuveau® and Letybo®, 50 Units for Dysport® and 40 Units for Daxxify®. Units of biological activity are never interconvertible between products, so a dose can never simply be carried across from one toxin to another.
The safest and most effective way to treat frown lines is still the labelled five-point glabellar map, injected with respect for depth and distance: deep medially, superficial laterally, lateral points at least 1 cm above the supraorbital ridge, and nothing closer than 1 cm above the central eyebrow. Start at 16–24 Units tailored to muscle strength, then reassess at two weeks. The 2024–2026 evidence has not replaced that approach — it has confirmed it, while sharpening what we know about the vessels underneath, the volume in the syringe, and how much of the outcome rests on the injector rather than the protocol.
That last point is the one worth acting on. The gap between a 5% ptosis rate and a 1% ptosis rate is not the product — it is training and repetition on live patients.
IAPAM has been training licensed healthcare professionals for over 20 years, with board-certified dermatologist instructors and hands-on injection practice on live models in a working Scottsdale clinic. If you want to build that confidence with the glabella and the rest of the upper face, explore our hands-on Botox® training and certification.
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Disclaimer: This guide is for informational and educational purposes only and does not constitute medical advice. Treatment plans, injection techniques, and dosing must be tailored to each patient by a qualified, licensed provider. Always follow product labeling, your scope of practice, and your state medical and nursing board regulations.
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