Anti-wrinkle injections: how many units do you actually need?

The honest answer is that most upper-face treatments fall between 20 and 60 total units, but no two faces use the same dose. How many units you actually need depends on the area being treated, the strength of the muscle underneath, your sex, and how much movement you want to keep in your expressions.

Below is how clinicians map units to muscles, why men almost always need more than women, and how we plan a dose for every new patient at CoLaz anti-wrinkle injections appointments.

A note before we go further: in the UK, botulinum toxin is a prescription-only medicine, so under advertising rules set by the Committee of Advertising Practice we cannot promote it by brand name to the public. This article talks about anti-wrinkle injections generically. Every figure below describes “units” of botulinum toxin type A in the standard sense, not any particular product.

Why are anti-wrinkle injections measured in units?

Anti-wrinkle injections are measured in units because botulinum toxin works by relaxing a specific volume of muscle, and the unit is how clinicians measure that dose precisely.

One unit is a fixed amount of biological activity in the toxin. A clinician decides how many units to inject at each point based on how strong the underlying muscle is, how deeply the line is etched, and the result you want. Different brands are not interchangeable on a one-to-one basis; their units are calibrated differently.

The same total dose, placed differently across the same face, gives different results. So “how many units” is only half the question; the other half is where they go.

How many units does the glabella (frown lines) take?

The glabella, the area between your eyebrows where the “11” lines form, typically takes 20 units in women and 30 to 40 units in men. This is the most studied area in injectable dermatology and the numbers are remarkably consistent across the evidence.

A foundational 1998 dose-response study on glabellar wrinkles found that 12.5 to 20 units across the area was the effective starting dose, with results lasting a median of 14 weeks. A more recent dosing review puts the current suggested dose for women at 20 units, and notes that dose ranges of 20 to 40 units were significantly more effective at reducing glabellar lines than 10 units alone.

The big variable here is sex. Men have larger, stronger procerus and corrugator muscles between the brows, and the same review found that 20 units of botulinum toxin was often ineffective in men, with better outcomes seen at 40, 60 and even 80 unit doses depending on muscle mass. We do not standardise by sex at CoLaz; we standardise by what the clinician can see and feel in the muscle on the day.

How many units does the forehead take?

The forehead (the frontalis muscle) typically takes 10 to 20 units in total. This is the area where dosing decisions matter most, because the forehead lifts the brow as well as creates horizontal lines, and over-treatment here is what causes the dropped-brow look people are most afraid of.

A consensus panel on tailored dosing for the forehead breaks the area into 12 zones and assigns 1 to 3 units per zone depending on three factors: whether the patient’s wrinkles are present at rest (hypertonic), worsen with movement (hyperkinetic), or appear only on full expression (kinetic). Women with average foreheads usually receive 1 to 2 units per point. Men, or anyone with hyperkinetic muscles, usually receive 2 to 3 units per point.

The most important rule on the forehead is that the dose is set in relation to what we have planned for the glabella, not in isolation. If we relax the frown muscles strongly without softening the frontalis enough, the brow has nowhere to “rest” and you can end up with a tense, lifted look. If we soften the frontalis too much without addressing the glabella, the brow drops. Balancing the two is the entire skill, and it is why an experienced clinician will not quote you a forehead-only dose without examining the whole upper face.

How many units do crow’s feet take?

Crow’s feet, the fan of lines that appear at the outer corner of each eye when you smile, typically take 10 to 12 units per side, so 20 to 24 units across both eyes.

A 2024 real-world outcomes study of upper-face aesthetic dosing reported a typical pattern of three injection points per side, with around 4 units per point, totalling 12 units per side and 24 across both eyes. That same study used 5 injection points on the glabella and 5 on the forehead, with the full upper-face treatment landing around 64 units total, a useful real-world anchor for what an experienced clinic actually delivers in a single session.

Crow’s feet respond well to anti-wrinkle injections because the orbicularis oculi muscle around the eye is thin and superficial. The dose required to soften it is small, the result is fast, and the risk of affecting how the eye opens or closes is low when the injector keeps to the standard points. The main individual variable is how dynamic your smile is. A bigger, more animated smile creates deeper crow’s feet at rest and may need the upper end of the 10-to-12 unit range per side.

What changes the dose for your face specifically?

Five things change the dose your clinician plans. None of them is your age, which surprises a lot of patients.

1. Muscle strength. Stronger muscles need more units. We assess this by asking you to frown hard, raise your brows and squint, while we watch and palpate.
2. Sex. Men typically need 1.5 to 2 times the female dose across the upper face because frontalis, procerus and corrugator muscles are larger.
3. Wrinkle pattern at rest. Lines present when your face is still (hypertonic) need a higher dose than lines that only appear with full expression.
4. Brow position. A lower-set brow needs a lighter forehead dose so the upper face stays open after treatment.
5. Your goal. A “frozen” look is not what most patients want; our default is to soften, not eliminate, expression.

This is why we do not sell a fixed unit package on day one. Two patients with identical wrinkles can need very different doses if their muscle strength and brow positions differ.

How long does each dose last?

A single course of anti-wrinkle injections to the upper face typically lasts three to four months, with some patients seeing five months at higher doses on the glabella. The duration is the same for all three areas, and it is largely fixed by the biology of botulinum toxin, not by the brand used.

The original dose-response data on glabellar treatment found a median duration of 14 weeks. Real-world clinical experience matches that closely. Patients who come in every three to four months typically see steady, consistent results; patients who wait six months or more often find the muscle has regained its full strength and the underlying lines have re-etched.

Most patients at CoLaz space treatments at four-month intervals, with the dose reviewed and adjusted at each visit based on how the previous treatment settled. This is why we do not lock you into a long-term package up front; the right unit count for visit two is the unit count that improves on what we learned at visit one.

Who can legally inject anti-wrinkle injections in the UK?

In the UK, botulinum toxin must be prescribed by a registered prescriber (a doctor, dentist, nurse prescriber or pharmacist prescriber) after a face-to-face consultation with you. The injection itself can be done by another trained practitioner working under that prescription.

That rule will tighten further. The House of Commons Library briefing on regulation sets out the proposed licensing scheme for England, and the Department of Health consultation classifies anti-wrinkle injections as an “amber” tier procedure: non-healthcare practitioners will only be able to deliver them under the oversight of a regulated healthcare professional.

When you book at CoLaz, your prescriber assesses you in person before any toxin is drawn up. We are registered with the JCCP and follow the standards published by Save Face, both Professional Standards Authority-recognised registers, alongside guidance from the British Association of Dermatologists.

How does CoLaz plan your dose?

Every new anti-wrinkle injection patient starts the same way: a free consultation with the prescribing clinician, an assessment of muscle strength and wrinkle pattern, and a written plan that includes the proposed unit count for each area before any prescription is issued.

If this is your first treatment, we usually start at the lower end of the range for each area. It is easier to add 2 to 4 top-up units two weeks later if the muscle is still doing more than you want, than to wait three months for a heavy dose to wear off. We see you for that two-week review as standard, included in the price of the first session.

If you have had anti-wrinkle injections before, bring the dose record from your previous clinician if you can. We will use it as a starting point and then adjust for what we see in your face that day, rather than copying the dose blindly.

For patients whose main concern is skin quality rather than expression lines, we will usually also talk about Profhilo or skin-boosting injectables as a complementary or alternative route. Anti-wrinkle injections are excellent for dynamic lines but they do not change the texture or hydration of the skin, and a sensible plan often blends the two.

If you want to find out what your specific unit plan would look like, book a consultation at your nearest CoLaz clinic. The assessment is free, the plan is written down before anything is prescribed, and we will not inject on day one unless the prescriber has confirmed the dose with you in writing.