How Long Does One Pen of Wegovy Last in Practice?

Step 1: understand what's in the box before you start

When your Wegovy pen arrives, you'll find a single pre-filled device containing enough medicine for four weekly injections. That's your month's supply in one pen. The pen is sealed at the factory with the dose already set, you cannot adjust it, and no mixing or measuring is required. A question our prescribers hear most weeks is whether a spare pen can be kept 'just in case' from the previous strength; the answer is to follow your prescriber's guidance, because using the wrong dose-strength pen without clinical sign-off is not something to decide alone.

Before your first use, check the pen hasn't expired, inspect the liquid through the window (it should be clear and colourless), and confirm you have everything you need: a clean injection site, the pen itself, and a way to dispose of the used pen safely. Our overview of Wegovy covers the full licensed schedule, including how dose strengths escalate over time.

The injection sites are the abdomen, the front of the thigh, or the upper arm. Rotating between them week to week reduces the chance of skin irritation building up at a single spot. Each injection is once weekly, on the same day each week if possible, at any time of day.

Step 2: tracking your four injections across the month

Because each pen contains exactly four doses, most people align the pen with a calendar month. Some people mark their injection day in their phone; others keep the pen in the fridge door and take it out around 30 minutes before use to let it reach closer to room temperature, which can make the injection more comfortable.

Storage is straightforward but important. The pen lives in the fridge at 2–8°C. There is a limited window during which it can be stored at room temperature if refrigeration is temporarily unavailable, the NHS semaglutide page is a good first reference, and the exact window is stated in the patient information leaflet supplied with your pen. Going beyond that window means the pen should no longer be used.

If you're planning travel, storage continuity matters. A brief guide to how long Wegovy lasts in the fridge and what the cold-chain requirements mean in practice is worth reading before you pack. The pen must never be frozen, a frozen pen is no longer safe to use.

Step 3: the fourth dose and what comes next

After your fourth injection, the pen is empty. Do not attempt to extract any remaining liquid; Wegovy pens are designed to deliver the correct dose each time, and the device stops functioning once the doses are used. Dispose of the pen in a sharps container, never in general household waste. A 1-litre sharps container is the right size for most home users on weekly injection treatment.

At this point you'll need your next pen. If your dose is being increased, your prescriber will confirm which strength comes next; you should not start a higher-dose pen without that clinical review. Under NICE's published recommendation for semaglutide (NICE TA875) the medicine is used as part of an ongoing treatment plan reviewed over time, with continuation assessed at six months. That review sits with your prescriber, not with the number of pens you've used.

If you want to understand how Wegovy sits alongside other weight management options, our weight-loss treatment overview sets out what's available as a private patient. The cost of an ongoing supply is covered on the Wegovy cost page, which explains how private pricing is structured and what a legitimate prescription-inclusive price actually covers.

What affects how smoothly each pen lasts the full four weeks?

A few practical things can disrupt the straightforward four-weeks-per-pen pattern, and our page on how long a Wegovy pen lasts walks through the most common reasons a pen may not reach its fourth dose. A pen that has been left outside the fridge too long, exposed to direct sunlight, or accidentally frozen is no longer reliable, even if it looks unchanged. Pen damage during delivery is rare when a pharmacy uses temperature-controlled tracked dispatch, but worth checking when you open the box.

Needle compatibility is another consideration some people overlook. Wegovy pens are used with compatible pen needles, it's worth confirming with your prescriber or pharmacy which needle length is right for your injection technique. The guide to Wegovy needle length explains the options. Changing the needle before each injection is important both for comfort and for hygiene; reusing needles blunts the tip, which makes injections more painful and increases local skin reactions.

If you'd like to understand how pen duration compares across different semaglutide formulations, the detail on how long a semaglutide pen lasts covers the broader picture, including how Ozempic (licensed for type 2 diabetes, not weight loss) differs in its pen design and dose volume from Wegovy.