What's inside a single Wegovy pen — and how does one pen fit into treatment?

Picture the pen sitting in your fridge on a Monday morning

You've just started Wegovy, and your first pen is at 0.25 mg, the opening strength in the titration schedule. The pen holds four of those doses. Each week, on the same day you chose at the start (Monday morning works well for a lot of people; it's easy to remember before the week gets going), you take the pen out, let it reach room temperature for a few minutes, pick your injection site (abdomen, thigh or upper arm) and inject. Then it goes back in the fridge.

The injection itself takes seconds. The pen is designed so that once you press the button and hear the click, the dose is delivered; the needle retracts and locks automatically. You don't need to see or handle a loose needle. After four injections, the pen is finished. At that point it goes into a sharps container (not the household bin) for safe disposal.

Rotating injection sites across the four doses in a pen reduces the chance of skin irritation building at one spot. The NHS patient information for semaglutide covers injection technique in practical detail, and it's worth a read before your first dose.

Why one pen won't look the same as the next one

The titration schedule for Wegovy runs across several months: 0.25 mg, then 0.5 mg, then 1.0 mg, then 1.7 mg, then 2.4 mg, each step held for roughly four weeks at a minimum before moving to the next, under prescriber guidance. The 7.2 mg maintenance dose, approved by the MHRA in April 2026, adds a further option for eligible adults. Each of those steps is a different pen. The pen you use in month one is not the same product as the pen you use in month four.

This matters for a practical reason: you cannot simply carry on with the same pen if your prescriber has changed your dose. The strength is set at the factory; there's no dial. So when a repeat is issued, it's issued for the specific strength appropriate to where you are in the schedule. Questions about when to move to the next strength, or whether to pause at a particular dose if side effects are troublesome, are clinical decisions, they sit with your prescriber, not with the pen itself.

If you'd like to understand how long one pen's supply is designed to last at your current stage, this page on Wegovy pen duration covers the timeline in full. And for details on exactly how much liquid one pen contains by volume, the pen volume page breaks that down clearly.

What to watch for across the month, and when to act

The most commonly reported side effects from Wegovy are gastrointestinal: nausea, constipation, diarrhoea, burping, indigestion. These tend to be most noticeable in the week or two after starting a new strength and often settle as your body adjusts. Fatigue and mild headache are also reported. None of this is a reason to abandon treatment without speaking to your prescriber, but it is worth knowing it can happen so the first week doesn't feel like something's gone wrong.

There are symptoms that do need prompt medical attention. Severe stomach pain that spreads towards the back (with or without vomiting) should be assessed the same day. The MHRA highlighted acute pancreatitis as a known, infrequent but potentially serious effect in a Drug Safety Update in January 2026. Signs of a serious allergic reaction (swelling, difficulty breathing, rapid heartbeat) also need urgent help. If you're uncertain, call 111.

Yellow Card reporting (at yellowcard.mhra.gov.uk) lets you report any suspected side effect directly to the MHRA. You don't need your doctor to do it; patients can report themselves. It's how the regulator spots emerging patterns, and it's worth knowing the option exists.

For a broader look at what treatment involves before you reach that first injection, the treatment overview page outlines the consultation and clinical process at nume.

Keeping the pen working, storage and handling in plain terms

An unused Wegovy pen should be kept in the fridge. Once you start using it, handling it once a week for your dose is fine; it doesn't need to come out in between. Travel (holidays, work trips) does require a little planning, because a pen left in a hot car or a bag without cooling can be damaged in ways that aren't visible. Your Patient Information Leaflet states the maximum time and temperature a pen can safely sit outside the fridge; follow that, not a general estimate, because the specific window matters and can vary by pen type, so if you're starting out it's worth reading about what to expect from your Wegovy 1 pen before your first dose.

Dispose of finished pens safely. In the UK, a sharps container is the correct route; many community pharmacies accept them. Never put a used pen in the recycling. If you're also managing other injectable medicines alongside your Wegovy prescription, it's sensible to talk to your prescriber about timing and site choices so the injections don't interfere with each other. If you'd like to know more about the fill and format of your device, the page on the Wegovy 1 ml pen explains what that volume means in practice. A broader look at how the Wegovy pen is designed and constructed can also help if you're new to self-injection and want to feel prepared. You might also find the nume clinical team page useful if you're weighing up whether an online prescribing service is right for you.

Wegovy is a prescription-only medicine. At nume, every consultation is read by a GPhC-registered Independent Prescriber, a real clinician, not an automated system. If you'd like to find out whether Wegovy is appropriate for you, start your free consultation with our prescribing team.