Units, syringes and millilitres: how injectables are measured, and why the amount varies

What is a unit of anti-wrinkle injection?

A unit is a measure of the dose of one product, not a universal quantity. An expert consensus notes that the units of different products are not directly comparable, so "how many units" is only meaningful for a named product, a named muscle and a named person. Anti-wrinkle injections work by relaxing small amounts of muscle, and the dose that does that depends on the muscle.

How many units will I need?

There is no set number. The dose follows the strength and pattern of each person's muscles: the forehead, between the brows and around the eyes each need their own amount, and men's facial muscles are, on average, larger. For the upper face the trend in expert consensus is towards lower doses, so we start with the smallest dose that does the job and add at the review if needed.

What does "baby" mean?

"Baby" is an informal name for smaller doses of the same medicine, placed to soften movement rather than stop it. The trade-off is a lighter effect that may wear off sooner than the usual three to four months, so it suits fine lines better than strong muscles.

What is a syringe or a millilitre of filler?

Dermal filler is a gel measured in millilitres and sold in syringes. The size of a syringe says how much gel is in it, not how much your face needs. How much is used depends on the area, the gel and how much support has been lost: there is no set amount of filler for a jawline, for cheeks or for lips,.

Why do two people have different amounts?

• Different anatomy: bone, fat, muscle strength and skin thickness differ from face to face.
• Different goals: softening movement is not stopping it, and a small change in definition is not a big change in volume.
• Different areas: each is planned on its own, and treating several areas is not the sum of a fixed amount for each.
• Different products: units and gels are not interchangeable, so an amount quoted for one does not carry over.

Why we start small and review

Anti-wrinkle injections take about two weeks to show fully, and filler settles as the swelling goes down. So we start modestly and decide any top-up at the review, two to four weeks later for filler. Adding is easier than taking away, although hyaluronic-acid filler can usually be dissolved if needed.

What this means for cost

We don't publish prices. The cost follows the plan: the areas treated and the dose or amount your face needs, which the doctor sets at the consultation. You know the full plan and its cost before you start. A price quoted before anyone has looked at your face, per unit or per syringe, is a price for a plan that does not exist yet.