Trapezius Botox injection points belong in the thick belly of the upper trap, the ridge you can pinch between the side of your neck and the tip of your shoulder, and they should stay shallow enough to land in that muscle. Where the points sit, how many units each side gets, and how deep the needle goes are three separate decisions, and the squarer neck-to-shoulder line you see from the front comes from matching all three to your shoulders, not from copying a chart.

If you're planning a trip to Seoul and comparing clinics, those same three are the questions worth asking before you book. A slim frame changes the depth question most, so I'll spend some time on that.

In this article, we'll cover where the points go when the goal is a squarer shoulder line, how many units and points studies use, how deep the injection should go and why that matters more for slender shoulders, the side effects and warning signs to know, and how one visit fits a travel itinerary.

Where Do Trapezius Botox Injection Points Go?

They go into the thickest part of the upper trapezius, along the ridge that runs out toward the bony tip of your shoulder, while staying clear of the hollow just above the collarbone. That ridge is the part of the muscle that builds the slope you see in photos.

A 2026 case report summarizes the usual target this way: injections should be restricted to anatomically defined safe zones, typically the 60%–80% upper trapezius along the line from the external occipital protuberance to the acromion.

Put simply, picture a line from the bump at the back of your head (the external occipital protuberance) to the bony tip of your shoulder (the acromion). The zone sits on the outer part of that line, over the ridge.

The authors explain why: "This area corresponds to the thickest portion of the muscle belly and avoids the lateral supraclavicular regions where the pleura is most superficial."

Supraclavicular means above the collarbone, and the pleura is the thin lining around the lungs. So the same map that puts the dose where the muscle is thickest also keeps the needle away from where the lung lining sits closest to the skin.

A nerve-staining study approached the question from inside the muscle, mapping where its nerve branches spread most densely (arborization). Its conclusion reads: "The authors recommend targeting these regions, where maximum arborization occurs, as the optimal and safest points for injecting botulinum toxin."

Does a nerve-based map change the outcome? In a randomized trial that compared it with a conventional map, the authors concluded that the nerve distribution method is more effective in reducing the trapezius muscle thickness, shoulder area proportion, and shoulder angle at three months.

Shoulder angle is the slope from neck to shoulder measured on a photo, which is the closest thing research has to a square line. To be fair about the limits, the same trial reported that The global aesthetic improvement scale feedbacks of the two methods showed no significant difference. Measured change and how people rated the look didn't move together.

For your own shoulders: shrug in front of a mirror with your fingers resting on that ridge. If it rises and turns firm, that's the muscle a map should be drawn on, on your own shoulders, while you shrug and relax. If it stays soft, much of the slope may not be muscle, and that's worth discussing before you spend a session on Botox.

How Many Units of Botox for the Trapezius?

There isn't one correct number. Published protocols vary, and in a small trial, a higher dose didn't produce a measurably slimmer result.

Study doses are usually counted per side. In an ultrasound-guided study of 20 women, Botulinum toxin type A was injected bilaterally (50 IU/side, 5 points/side).

IU stands for international units, the same units you see on a Botox quote. The points in that study weren't placed from a template.

The team used ultrasound to locate the thickest point of trapezius, followed by labelling the other four points around the first point.

In a split-shoulder trial, volunteers were randomly injected with 30 units of Incobotulinum toxin A and Onabotulinum toxin A in each trapezius muscle guided by ultrasound, one product on each side.

In another randomized trial, women with trapezius hypertrophy (an enlarged trap) were randomized into group A (n = 10, 40 units) and group B (n = 10, 80 units).

The authors reported that no statistically significant differences or complications were observed between the groups. The groups were small, so treat that as a caution against assuming more is better, not proof that dose never matters.

Points matter for a different reason than units. Botox spreads a short distance from where it's placed, which is why protocols split the dose across several points instead of putting it all in one spot.

A Korean anatomy-and-clinical study gave one concrete pattern. The authors wrote: "we recommended injecting into six points separated by 2 cm in sections b and c of the upper trapezius muscle."

Sections b and c are zones the authors marked out along the upper trap.

So when you compare quotes, a single total tells you less than it seems. Ask how many units go on each side and how many points carry them. If one shoulder is visibly bulkier, uneven numbers can be part of a sensible plan. Individual results vary, and the plan should follow your muscle rather than a set figure.

How Deep Should Trapezius Botox Go?

Into the muscle and no further. On most shoulders that's a short distance under the skin, which is why needle length and depth control are part of the design, especially if you're slim.

The upper trap isn't a deep muscle. The same 2026 case report notes that skin-to-trapezius midpoint distance is frequently around 1 cm.

Under the muscle lies the top of the chest. The report explains that in slender patients, the skin-to-pleura distance can be remarkably short.

That report described a woman who developed a pneumothorax, a partly collapsed lung, after cosmetic trap Botox. The authors stated that iatrogenic pneumothorax has not been previously documented for this cosmetic indication. Iatrogenic means caused by a treatment.

In her case, follow-up ultrasound revealed a skin-to-pleura distance of only 2.27 cm at the injection site, highlighting the stark mismatch with the 4.8-cm needle used.

In their conclusion, the authors wrote: "Pneumothorax is a rare but significant complication of cosmetic trapezius BoNT injections."

Their advice on prevention was practical: practitioners should adhere to anatomically defined safe zones, select conservative needle lengths, and utilize ultrasound assistance when necessary, particularly for thin patients.

They also stressed a hands-on step: "Palpation and grasping of the muscle belly are essential to verify depth and avoid hollow supraclavicular areas."

Here's the variable worth understanding before you book: the right depth isn't a fixed number. It's the muscle that can be held between two fingers at each point. The less padding you have over your collarbone and shoulder, the less room there is below that muscle.

If you're slim, that's not a reason to rule out trapezius Botox, and the case is reported as rare. It is a reason to mention your build when you send photos and to ask at the consultation how the muscle will be located at each point and how the needle depth is kept within it.

Side Effects and Risks of Trapezius Botox

A tired or weaker feeling when lifting is a known side effect, because the trap helps raise and steady the shoulder; why that happens is covered in Trap Botox Side Effects. The rarer, depth-related risk is the one covered above.

In the nerve-map trial, the authors noted that The patients did not experience severe side effects. That trial was small, so it can't rule out uncommon problems.

If you lift overhead or carry heavy loads for work, a dip in lifting strength matters more, so timing deserves a conversation. If you've had Botox anywhere in recent months, bring the date, area, and product.

Know the warning signs. The case report's authors wrote that Pneumothorax must be suspected if sharp pain occurs during the procedure, followed by acute respiratory distress.

• During or soon after the injections: sharp chest or back pain, or shortness of breath, means telling the doctor at once and getting emergency care.

• In the days after: trouble swallowing, speaking, or breathing, or weakness that spreads beyond the shoulder, needs medical care right away.

• At the injection points: tenderness or bruising that gets worse instead of better is a reason to contact your provider.

Fitting Trapezius Botox Into Your Seoul Trip

As long as you weren't sedated that day, there's no reason to push back your flight home because of trapezius Botox.

Sightseeing and sleeveless photos are a separate question. How the injection points look the next day can vary, so it's worth going over your plans at the consultation.

One visit is a real start, but the change is gradual rather than instant. In the ultrasound-guided study, obvious appearance changes were revealed at 12 weeks after surgery, where surgery means the injection session.

So you start the change in Seoul and judge it at home. If you want the squarer line for an event, count back from that date rather than from your flight.

• Before you fly: a straight-on front photo with arms relaxed and chin level, a back photo while shrugging, your travel dates, and a note on your build and whether you lift overhead.

• On the day: write down the product, units per side, points per side, and the date.

• Back home: retake the same front photo in the same pose and light weeks later.

If something looks or feels off after you're home, you can send photos and a short description to our WhatsApp consultation channel. If symptoms are significant, such as trouble breathing or swallowing or weakness that's spreading, see a local doctor first.

The Bottom Line

• Injection points go into the thickest part of the upper trap, along the ridge and away from the hollow above the collarbone.

• Unit counts vary across studies, and more units hasn't meant a slimmer result, so ask for units and points per side.

• Depth should stay within the muscle, and slender shoulders leave less room below it.

• The line changes over weeks, so judge it with matching front photos.

Like any procedure, it comes with trade-offs, mainly a temporary dip in lifting strength.

Before any trapezius Botox, check three things on your plan: where the points sit on the ridge, how many units go on each side, and how depth is confirmed at each point, by feel, by ultrasound, or both. If all three answers refer to your shoulders rather than a standard pattern, the design was made for you.

Ultimately, the choice depends on your shoulders, your goals, and your travel dates. If you'd like to discuss it with Beautystone, a short WhatsApp message is enough. To start, send a WhatsApp message like this: "I'm in Seoul from [dates]. I'd like trapezius Botox for a squarer shoulder line. Here's a front photo and a shrugging back photo. My build is [slim / average]."