20 ml semaglutide: understanding this volume and what it means for you

The decision you're actually facing when you see a volume figure

Most people searching for "20 ml semaglutide" are trying to answer one of two questions: is this a real product I can obtain, or is something I've been quoted correct? Both are reasonable questions, and neither has a reassuring answer when the unit is millilitres.

Licensed semaglutide for weight management in the UK (Wegovy) is supplied as a pre-filled, pre-set injection pen. Each pen delivers one weekly dose, calibrated to the milligram. The dose your prescriber works towards will sit somewhere on a schedule that begins at 0.25 mg and, depending on the pen format, can reach up to 7.2 mg at the highest approved maintenance level, following the full Wegovy titration pathway. The volume of liquid inside each pen is a pharmaceutical manufacturing detail; it is not a number that appears on prescriptions, patient information leaflets, or any part of the clinical conversation.

So when a listing describes semaglutide in millilitres, that is not a licensed UK product presentation. It typically points to one of two things: a compounded or unlicensed preparation, or a straightforward misunderstanding of how the medicine is measured. In either case, the volume figure is not the right frame for your decision.

What unlicensed compounded semaglutide means, and why the MHRA is concerned

Compounded semaglutide, sometimes sold as a vial measured in millilitres for use with a syringe, has grown in visibility alongside the legitimate shortage of branded pens. It is not the same product. The MHRA has issued clear public guidance warning that semaglutide-based products sold without a valid UK marketing authorisation (including those described by volume rather than by the licensed brand and dose) fall outside the regulated supply chain. Patients have no assurance of the concentration, sterility, or actual active content of what they are injecting.

The MHRA's guidance on GLP-1 medicines for weight loss, published on GOV.UK, is explicit: suspect products should be reported via the Yellow Card scheme, and anyone who has used an unlicensed preparation and feels unwell should seek medical attention promptly. Sellers offering these products without a valid prescription and without clinical oversight are operating outside UK law.

This is not a theoretical concern. Enforcement actions through 2025 identified roughly 20 million doses of illegally traded weight-loss medicines, worth around £45 million, including the first illicit UK site producing counterfeit tirzepatide pens. The pattern with semaglutide follows the same logic: unlicensed volume-based vials look affordable, but the risk profile is entirely different from a product that has passed MHRA scrutiny.

How licensed semaglutide is actually presented, and what the ml figures really represent

Each Wegovy pen contains a specific volume of solution, set by the manufacturer for that dose strength. For example, a 0.25 mg dose pen contains a different fill volume than a 2.4 mg pen. But neither figure is 20 ml, and neither is the number a prescriber or pharmacist uses when discussing your treatment. If you've seen volume breakdowns like 1 ml semaglutide, 2 ml semaglutide, 3 ml semaglutide, or 5 ml semaglutide referenced online, these are typically attempts to describe the concentration of unlicensed preparations or to reverse-engineer the content of licensed pens, neither of which is a useful frame for your care.

What does matter is the milligram dose, the titration schedule your prescriber sets, and whether the pen you receive comes from the licensed UK supply chain. A pharmacy registered with the GPhC, which you can verify at the GPhC pharmacy register, can only dispense Wegovy against a valid prescription, in the manufacturer-prepared pen format, at the dose written by the prescriber. That is the only safe version of this medicine available in the UK.

For context on how the UK cost of treatment is structured, the weight-loss treatments page sets out what a private prescription includes. One transparent price covers consultation, the prescription itself, and delivery, with no separate fees added later. That framing matters because volume-based products often appear cheaper upfront; the comparison is not like-for-like.

What a genuine clinical assessment looks like, and why it starts with mg, not ml

A prescriber assessing you for semaglutide will look at your BMI, weight-related health conditions, medicines you already take, and any contraindications. They will not ask how many millilitres you want. The conversation starts with your health picture, and the dose they write (expressed in milligrams) follows from that. NHS guidance on semaglutide via the NHS medicines pages explains the licensed dose pathway clearly, and it is measured throughout in milligrams.

At nume, every consultation is read personally by a GPhC-registered Independent Prescriber the same day it is submitted, a real clinician reviews it, not a piece of software routing your answers to an auto-approval queue. If you order before noon on a working day and your prescription is approved, the pen is dispatched the same afternoon by DPD and arrives the next working day in plain packaging. You'll get a DPD tracking link on your phone as soon as it leaves the pharmacy. For anyone unsure whether they are eligible, the weight-loss overview page explains the licensed eligibility criteria for both Wegovy and Mounjaro in plain terms.

If you have questions before starting, our frequently asked questions cover the most common concerns, and our support team is available seven days a week. The right place to start, though, is a consultation with a prescriber who can look at your specific situation.