What Happens If Wegovy Is Not Refrigerated

Step 1, Understanding why temperature matters for semaglutide

Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist made from a modified protein structure. Like all protein-based medicines, it relies on that structure remaining intact to bind correctly to its target receptors in the body. Heat disrupts that structure through a process called denaturation: the protein folds in on itself incorrectly, losing its ability to work as intended. The NHS medicines information for semaglutide confirms that Wegovy pens must be stored in a refrigerator at 2°C to 8°C before first use.

One misconception worth clearing up: a pen that has been left out does not necessarily look different. The liquid may remain clear, colourless, and free of particles, yet still contain degraded medicine. Visual inspection alone is not a safe way to decide whether a pen is still suitable. This catches people out regularly, the pen looks fine, so they assume it is fine. That assumption is not reliable for a protein-based injectable.

It is also worth knowing that cold is not automatically safer than warmth. A pen exposed to freezing temperatures (left in a car overnight in winter, or accidentally placed against the back wall of a fridge where it froze) is also unsuitable for use. Freezing causes ice crystals to form within the solution, physically disrupting the protein. A pen that has frozen must be discarded, full stop. You can read more about the broader storage requirements on our Wegovy refrigeration guide.

Step 2, The approved room-temperature window and what happens when it passes

Wegovy is not strictly a medicine that must live in the fridge every moment before it is used. Novo Nordisk and regulators recognise that people travel, carry pens to work, and sometimes forget to return a pen to the fridge. For this reason, the SmPC and Patient Information Leaflet include an approved period during which a pen may be kept at room temperature, below a defined maximum temperature, after which it must either be used or discarded.

The exact duration and temperature ceiling are specified in the leaflet that comes with your pen, and those figures should be treated as binding. Our page on whether you can use Wegovy left at room temperature goes into the practical questions around this in more detail. The key point here is that once the approved window closes, the pen should not be returned to the fridge and used later as though the clock reset. It cannot. The window is cumulative: time spent at room temperature across multiple occasions counts together.

Beyond that window, the medicine's potency is no longer guaranteed. Using a degraded pen does not mean you will be harmed in the way a counterfeit product might harm you, but it does mean you may be injecting less active medicine than the dose printed on the pen, which undermines the purpose of treatment. If you are unsure whether your pen is still within its approved period, our guide on whether Wegovy goes bad outside the fridge covers the specifics. The same question comes up frequently for semaglutide in other forms, and our guide on whether semaglutide can be used if it has not been refrigerated addresses those concerns in detail.

Step 3, What to do if your Wegovy was not refrigerated properly

First, check your Patient Information Leaflet. The leaflet shipped with every Wegovy pen states the room-temperature storage window clearly. If you know roughly how long the pen was out and the conditions it was in, you can compare that against the approved limit. If you are within it, the pen is generally considered suitable for use, but if you have any doubt, contact your pharmacist or prescriber before injecting.

If you believe the pen has been outside approved conditions for longer than permitted, do not use it. Contact your prescriber or pharmacist to explain what happened. In many cases a replacement can be arranged, and your clinical team can confirm the right next step for your dosing schedule. This is particularly important if you are mid-titration, since a missed dose at the wrong stage can affect how your body responds to the next step. Our page for people whose Wegovy was not refrigerated correctly covers the replacement process in more practical terms.

Disposing of a pen you cannot use: remove the needle carefully and place the pen and needle in an appropriate sharps container before disposal. Do not put used or damaged pens in household waste. Your pharmacist can advise on your local disposal route.

For anyone considering starting treatment, or reviewing whether Wegovy is the right option, our weight-loss treatment overview explains what is licensed and how clinical assessment works in a private setting. Wegovy is a prescription-only medicine and always requires a prescriber's involvement, not just at the first prescription, but at each review. The NHS patient information for semaglutide, available via the NHS medicines library, is also a reliable reference for storage and side-effect questions.