Can expired Wegovy still be used?

No — do not use expired pens. Potency and sterility can’t be guaranteed after the expiry date, which risks reduced effect and unsafe dosing. Check both the carton and the pen, and plan refills so you don’t run short. Return expired or questionable pens to a pharmacy for safe disposal, and ask your clinic to advise on replacements to avoid gaps in weekly dosing.

Why expiry dates matter

All medicines come with expiry dates, and injectable medicines like Wegovy are no exception. The expiry date is set after careful stability testing by the manufacturer and reviewed by regulators such as the MHRA. Once the date has passed, there is no guarantee that the medicine remains effective or sterile. Semaglutide, the active ingredient in Wegovy, is a protein-based drug that can degrade over time, especially if exposed to fluctuating temperatures. Degraded proteins may lose their therapeutic effect, and in rare cases could trigger unexpected immune responses. NHS patient advice is clear: never use expired medicines, as their safety cannot be assured. In the context of Wegovy, using an expired pen could mean weaker appetite control, missed weight loss targets, and unnecessary risk.

Risks of reduced potency and contamination

Expired Wegovy may no longer contain the full intended dose. Semaglutide levels could be reduced, which means patients may inject a pen thinking they are receiving the correct amount but in fact are underdosing. This undermines consistency, which NICE TA875 emphasises as critical to achieving results in structured weight management programmes. Clinical trials such as STEP and SELECT depended on precise, controlled dosing, which could not have been guaranteed with expired supplies. Beyond potency, sterility is another risk. Once a product is beyond its expiry date, the protective packaging and preservative system may no longer be effective. This increases the chance of bacterial contamination, which could cause infections at the injection site or more serious illness. Even if the pen looks normal, it may not be safe to use.

Checking packaging and planning ahead

Patients are advised to check both the carton and the pen itself for expiry dates. It is possible for a pen to have an earlier date than the box, as packs may contain multiple units. Planning ahead avoids running out and having to consider expired pens as a “backup.” NHS services encourage patients to order repeat prescriptions in good time, allowing for pharmacy supply delays. GLP-1 medicines have faced shortages in recent years, as noted by NHS England and MHRA alerts, making advance planning even more important. Some patients have found it helpful to keep a simple calendar log of when each pen is due to expire, ensuring they rotate stock effectively. Others use reminder apps or note expiry dates directly on the packaging with a marker. These small habits help avoid being caught out by surprise when a pen is suddenly out of date.

Safe disposal of expired pens

Expired or questionable pens should never be used and must also be disposed of safely. Pharmacies in the UK offer take-back schemes, allowing patients to return unwanted or expired medicines for proper destruction. This includes injectable devices such as Wegovy pens. NHS services stress that expired pens should not be placed in household rubbish or recycling, as they may still contain drug residue and a sharp needle once used. A sharps bin is the safest place if one is already in use at home, but otherwise, returning to the pharmacy is the standard pathway. The MHRA underlines the importance of safe disposal not only for individual safety but also for environmental protection. By following disposal advice, patients can reduce the risks of accidental exposure for children, pets, or waste handlers.

Avoiding treatment gaps

Missing doses because of expired pens can be frustrating, but there are safe ways to manage the situation. NHS guidance follows the “five-day rule” for missed doses: if you realise within five days, inject as soon as possible; if more than five days have passed, skip and wait until the next scheduled dose. Clinics may be able to issue replacements promptly if contacted in time. NICE TA875 highlights that semaglutide should always be delivered within structured services, and this includes ongoing monitoring to reduce the likelihood of treatment interruptions. Some patients report that keeping a small buffer supply, where possible, provides reassurance in case of delays. However, NHS staff stress that replacement supplies must be prescribed and that expired pens should never be relied on as “back-up stock.”

What the evidence shows overall

The evidence is clear: expired Wegovy should not be used. Stability testing, NICE guidance, and NHS advice all point to the same conclusion — expired pens carry risks of reduced potency, contamination, and treatment disruption. The STEP and SELECT trials relied on strict adherence to dosing schedules with in-date supplies, reinforcing that this medicine only works when handled correctly. For patients, the safest approach is to check expiry dates regularly, plan refills early, and return expired pens to a pharmacy for safe disposal. What the evidence shows overall is that careful planning prevents gaps and ensures treatment remains both safe and effective.