100 Units of Semaglutide: Why the Measurement Confuses People

The myth: semaglutide comes in units, so "100 units" is a real dose

This idea circulates on forums and social media, and it has a source: insulin has been measured in units for decades, and many people who have managed diabetes are familiar with drawing up 10, 50 or 100 units in a syringe. Semaglutide is also used in diabetes treatment (as Ozempic), which muddies the water further. The confusion deepens when unlicensed compounded semaglutide products (some sold online, some obtained abroad) are described in unit terms rather than milligrams, often because they have been dissolved and diluted in ways that require the user to calculate a volume to draw up. That is not how any licensed UK semaglutide product works.

Wegovy, licensed by the MHRA for weight management in the UK, arrives as a pre-filled pen. The dose is fixed and pre-set. You press a button; a precise milligram amount is delivered. There is no vial, no syringe, no unit calculation. If a product you have seen described involves drawing up "100 units" of anything and injecting it for weight loss, it is not a licensed UK medicine. The Wegovy treatment page explains the actual dose pathway in full.

The MHRA has been explicit about the risks of unlicensed compounded semaglutide: products outside the regulated supply chain have been found to contain incorrect concentrations, impurities, or entirely different substances. Reporting a suspect product via the Yellow Card scheme is the right step if you have encountered one.

What "milligrams" actually means in practice for Wegovy users

The licensed starting dose of Wegovy is 0.25 mg once weekly, escalating through 0.5 mg, 1.0 mg, 1.7 mg and up to 2.4 mg over approximately four months, with a prescriber guiding each step. The 7.2 mg single-dose pen, approved by the MHRA in April 2026, represents the current maximum. Every pen in that sequence is clearly labelled, no unit maths, no dilution, no syringe required.

To put 100 units in context: if someone were using an insulin syringe calibrated for U-100 insulin (100 units per millilitre), drawing up 100 units would mean drawing up 1 ml of fluid. That tells you nothing about the milligram content of whatever is in the vial, which depends entirely on the concentration of that specific product. Compounded semaglutide products sold online vary wildly in concentration, and users have no reliable way to verify what they are actually injecting. This is precisely why the NHS patient information for semaglutide emphasises using only medicines prescribed by a clinician and supplied through a regulated pharmacy.

For anyone wondering what Wegovy costs through a private route, the context on Wegovy pricing in the UK is worth reading before making a decision based on price alone.

What the licensed treatment schedule actually offers

The clinical trial programme behind Wegovy is substantial. The STEP 1 trial, published in the New England Journal of Medicine, followed adults with obesity over 68 weeks and found an average weight reduction of around 15% at the 2.4 mg maintenance dose alongside lifestyle changes. The more recently approved 7.2 mg dose (studied over 72 weeks) produced average losses approaching 20.7%, narrowing the gap with tirzepatide results. These figures come from tightly controlled trials with licensed products at known, consistent milligram doses. Compounded or unlicensed versions cannot offer comparable evidence, because they have not been through that process.

A prescriber assessing your suitability for Wegovy takes into account your BMI, any weight-related health conditions, your medical history and your current medicines, including, notably, whether you take an oral contraceptive, since tirzepatide (not semaglutide) carries specific guidance about adding non-oral contraception during early treatment. That kind of individual clinical judgement is what makes a prescription meaningful. It is also why the question of which dose you start on is answered in a consultation, not a forum thread. Our clinical team works through exactly these details with every patient before anything is prescribed.

If you have been looking at lower dose points and wondering how the escalation works in practice, the 5-unit query page covers the same measurement confusion at a different number, and the broader weight-loss treatment overview sets out the options available through nume.

The safety question behind the search

People searching for "100 units of semaglutide" often fall into one of two groups: those who have encountered an unlicensed product and want to know if it is legitimate, and those who are trying to understand a dose they have been quoted somewhere online. Both groups deserve a straight answer.

For the first group: if a product is described in units rather than milligrams, requires you to draw it up yourself, and arrived without a face-to-face or video-verified clinical assessment, it sits outside the licensed UK supply chain. The MHRA has repeatedly warned that fake and compounded GLP-1 pens have caused hospitalisations. That is not a theoretical risk.

For the second group: the licensed schedule for Wegovy is a milligram pathway, titrated by a prescriber. There is no equivalent "100 units" step. If you are mid-treatment and unsure about your dose, the right person to ask is your prescriber, not a search engine. Queries about specific amounts, such as what 10 units of semaglutide actually corresponds to or what is meant when 12 units of semaglutide is mentioned, are covered in dedicated pages if you want to understand the measurement confusion in more detail. Our FAQ page covers common mid-treatment questions, and the support team is available seven days a week. Worth checking before changing anything.