Semaglutide dose in units: reading the numbers on your pen

You're staring at the pen and the number doesn't match your prescription

Picture this: your prescription says 0.5 mg, but when you pick up the pen you see a dial that can turn to 40, 60 or 80. It's a genuinely disorienting moment, and it trips up a lot of people. A question our prescribers hear most weeks is some version of "the number on my pen doesn't match what I was told to take, am I doing it wrong?"

The short answer is no. UK Wegovy pens are pre-set or pre-filled to deliver a specific dose of semaglutide expressed in milligrams. The numbers visible on the dose window are device graduations, part of the pen's mechanical design, not an independent unit of medicine. They tell you how far the plunger has travelled inside the cartridge. Your mg dose (the clinical figure) is what appears on the prescription label and in the NHS semaglutide patient information.

So when someone searches for "semaglutide dose in units", they're usually trying to reconcile these two sets of numbers. The answer is that the mg figure is always the authoritative one. If you want to understand how a specific fill quantity breaks down, the page covering how many units are in 5 mg of semaglutide walks through the concentration maths in plain terms. If you are unsure what the dial markings on your specific pen represent, the Patient Information Leaflet packaged with the pen explains the device step by step.

What the licensed mg doses actually are, and how they progress

Wegovy's licensed dose schedule in the UK moves in stages, each lasting around four weeks, under prescriber direction. It starts at 0.25 mg (a tolerability step whose job is to let your system adjust, not to drive significant weight loss) and climbs through 0.5 mg, 1.0 mg and 1.7 mg, reaching the 2.4 mg maintenance dose. The full Wegovy dose schedule covers each stage in detail.

In January 2026 the MHRA approved a higher 7.2 mg dose, and a dedicated single-dose 7.2 mg pen followed in April 2026. Trial data at that dose showed around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide's headline figures. The BNF entry for semaglutide lists the full licensed schedule for UK clinicians.

None of these dose steps should be self-managed. Titration timing and the decision to move up (or stay put) sits with your prescriber. If a conversion between semaglutide dosage in units and mg is prompting you to consider adjusting your own pen, pause, that's a conversation for your clinical team, not a calculation exercise.

For anyone who wants to understand specific conversions in more depth, the page on what 2.4 mg semaglutide looks like in unit terms works through the maths for the maintenance dose, using the pen's actual concentration figure.

Why "units" means something different for semaglutide than for insulin

The confusion is partly imported from insulin. People who manage diabetes are accustomed to dialling up insulin in international units (IU), where the unit is a precise pharmacological measure of biological activity. Semaglutide is not measured or prescribed in IU. Its dose is a mass (milligrams of drug per injection) and the pen delivers that mass based on the concentration of solution in the cartridge.

That concentration matters when someone tries to convert semaglutide units to mg. A pen with a concentration of 1.34 mg/ml will produce a different mg figure per graduation mark than one with a higher or lower concentration. This is exactly why the maths differs pen to pen, and why generic "units to mg" tables you might find online can mislead you if they don't specify which product and which concentration they're using.

The safest approach is always to go back to the leaflet inside the box. If you're switching between pen formats (for instance, moving from the 2.4 mg pen to the newer 7.2 mg single-dose device) your prescriber will walk you through any practical changes. You can also explore the Wegovy overview for a plain-English account of how the medicine works and what to expect.

If you've come across information about cost while researching your options, the weight-loss treatments page sets out what private treatment through a regulated UK pharmacy actually involves.

Getting the right dose confirmed before you inject

Semaglutide is a prescription-only medicine in the UK, which means a prescriber (not a calculator, not a forum post) is the correct authority on what dose you should be using. That applies both when you start treatment and each time a dose change is considered.

At nume, every consultation is reviewed the same day by a GPhC-registered Independent Prescriber. Before any dose increase, your prescriber checks your progress, weight and any side effects, a clinical re-review, not an automatic step-up. That process is described on our about us page, and our clinical team oversees every prescription personally.

If you have a specific conversion query (for instance, you've seen a number quoted online and want to know what it translates to in mg) the pages on 10 units to mg and 30 units to mg work through those examples with the correct pen-concentration context. And if you're ready to begin, speak to our prescribers to start your free consultation.