Does Semaglutide Go Off — and How Do You Know?

The decision you're probably facing: use it or replace it?

Most people asking whether semaglutide goes off are standing in front of a pen with a concern. Maybe it was left out overnight. Maybe it has been sitting in the fridge since a missed dose, and the date is coming up. The honest answer is that expiry dates and storage conditions are two separate questions, and both count.

The expiry date on a Wegovy pen or tablet pack is the manufacturer's guarantee of potency under correct storage conditions. Novo Nordisk sets that date based on stability data for product kept refrigerated and away from light. If storage conditions were not met (the pen sat in a warm car for several hours, or was accidentally frozen) the medicine may have degraded independently of the date. Degraded semaglutide is not necessarily dangerous, but it may be less effective, and you would have no way of knowing how much less.

If the date has passed, the answer is straightforward: do not use it. Contact your pharmacist or prescriber and arrange a replacement. If the date is fine but storage conditions were compromised, the same applies. The NHS semaglutide medicines page is a reliable starting point, and the Patient Information Leaflet inside your pack gives the exact temperature limits and room-temperature windows for your specific product.

How semaglutide degrades (and why heat is the main culprit

Semaglutide is a peptide) a chain of amino acids with a fatty acid attached. Like most biological molecules, it is sensitive to temperature and, to a lesser degree, light. Refrigeration (2–8°C) slows the molecular movement that causes peptides to unfold or aggregate. Freezing, counter-intuitively, can cause damage through ice crystal formation, which is why a pen that has been frozen should be discarded even if the solution looks normal when it thaws. You can read about the full stability data in the Wegovy SmPC on the electronic Medicines Compendium, which is the authoritative source for storage requirements.

Heat accelerates degradation. A pen left on a kitchen counter in summer, or packed in hold luggage on a warm flight, may experience temperatures well above 30°C. The Patient Information Leaflet specifies the maximum temperature and the number of days a pen may spend outside the fridge after first use, that figure is different for the injection pen and the tablet formulation, so check yours specifically rather than relying on a general rule.

Light matters less than temperature but is still worth managing. Keep pens in their original outer packaging when not in use, even inside the fridge. The outer carton is not just branding; it provides a degree of light protection that the pen cap alone does not.

Tablets versus pens: does the form affect how quickly it goes off?

The Wegovy tablet (oral semaglutide co-formulated with an absorption enhancer) was approved by the MHRA in June 2026 as the first oral GLP-1 weight-management medicine licensed in the UK. One practical difference from the injection is storage: the tablets do not require refrigeration and are kept at room temperature. That makes them somewhat simpler to manage day-to-day, though they are not immune to expiry or environmental damage, and if you want a detailed look at whether Wegovy goes off and what affects its shelf life, that question is covered in full on its own page.

Moisture is the main enemy of tablet formulations. A bathroom cabinet above a steaming shower, or a bag left in a damp gym locker, can compromise a blister pack over time even without reaching the expiry date. The practical solution is the same as for any tablet: a cool, dry place, away from direct sunlight, in the original packaging.

For anyone weighing up the injection and tablet forms for reasons that include travel or storage convenience, the Wegovy treatment overview covers both in more detail. Specific cost questions are addressed on the Wegovy cost page. And if you are curious how the trial evidence stacks up for the oral form, the OASIS 4 trial summary explains what the data showed at 64 weeks.

What to do with an expired or compromised pen

Disposal is a separate question from storage, and it matters both for safety and for the environment. Used or expired pens and needles should go into a sharps container rather than general household waste or recycling. Your pharmacist can advise on local disposal routes; some areas have community sharps collection schemes.

If you suspect a pen has been compromised (left in a hot car, frozen by mistake, dropped and cracked) do not simply discard it in the bin either, because the needle tip poses an injury risk. Contact your pharmacist or our team for guidance. Questions about a dose you are unsure about should always go to your prescriber, not be decided alone; our aftercare team is available seven days a week for exactly this kind of query.

There is also a broader safety point here. The MHRA has issued warnings about counterfeit weight-loss pens sold online, some of which have contained entirely different substances. A pen from an unverified seller is a risk not just of ineffectiveness but of real harm. The only safe route is a prescription from a registered prescriber and supply through a pharmacy you can verify on the GPhC pharmacy register. If you are considering starting treatment or have questions about your current prescription, our semaglutide information page sets out how the process works at nume. Semaglutide's effects and how long they last is a related question many people have; how long semaglutide stays active covers that separately.

When you are ready to speak with a prescriber, check your eligibility with a free consultation and a clinician will review your case the same day.