How to know if your Wegovy pen has frozen — and what to do next

Step 1, Look at the liquid before you do anything else

Hold the pen up to a good light source. In a normal, unaffected pen, the semaglutide solution is clear and colourless. It may have the faintest hint of yellow, which is fine, but it should be entirely transparent with no particles floating in it.

If the liquid looks white and cloudy, milky, or you can see any solid matter or ice crystals, stop. That appearance is the clearest sign that the pen has frozen, or at minimum that something has changed the medicine's structure.

One thing worth saying clearly: cloudiness alone doesn't always mean freezing. Some people have assumed that slight haziness is just how the product comes. It isn't. A semaglutide pen that is in good condition is consistently clear. Any cloudiness is a reason to pause and work through the rest of these steps before injecting.

You can find the normal appearance described in the Mounjaro and Wegovy SmPCs on the eMC (search for Wegovy) alongside the full storage guidance. The NHS also covers semaglutide storage on their semaglutide medicines page.

Step 2, Check where the pen has been stored

Fridges aren't always uniform. The coldest spots tend to be against the back wall and near the bottom, both areas where temperatures can dip below 0°C if the thermostat is set too low or the fridge is overpacked and air can't circulate. If your Wegovy pen was sitting directly against the back wall, there's a real chance it reached freezing point even if the rest of the fridge felt fine.

Check your fridge temperature with a thermometer if you're uncertain. The recommended storage range is 2°C to 8°C. Below 2°C is not automatically a freeze, but it's a warning sign, and anything at or below 0°C is a problem.

Freezer compartments are an obvious risk, but the more common culprit is simply a miscalibrated domestic fridge. If you've recently moved house, had the fridge serviced, or the pen was stored in a shared fridge at work, it's worth being methodical here.

Details about exactly how long a Wegovy pen can tolerate room-temperature storage (relevant if you've been travelling) are in the Patient Information Leaflet. Our guide to what to know when taking Wegovy covers storage alongside other day-to-day questions.

Step 3 (Allow time, then look again

If you have reason to believe the pen may have frozen but it's now back at room temperature, wait until it has fully warmed) around 30 minutes out of the fridge is typical, then repeat the visual check from Step 1.

A pen that has been frozen and then thawed will generally not return to its normal clear appearance. The protein structure of the semaglutide molecule can be disrupted by ice crystal formation, and that damage doesn't reverse when the temperature rises again. So if the pen still looks cloudy or shows any particulate matter after warming, the answer is the same: don't inject it.

If, on the other hand, the liquid has returned completely to its normal clear appearance and there's no physical evidence of damage, the pen may be usable, but this is precisely the situation where it helps to read our Wegovy things to know guide before deciding anything, and then discuss the specific storage history with your prescriber or pharmacy. They can advise based on what you describe. Getting that reassurance matters, because injecting a compromised biological medicine carries its own risks entirely separate from missing a dose.

For questions about how to confirm your injection has gone in correctly once you do use a good pen, our page on how to know your Wegovy injection went in covers that specifically.

Step 4, What to do if the pen is damaged

Do not use it. That's the short version. A pen that has frozen and shows the signs above should be disposed of safely (ideally in a sharps container) and replaced before your next scheduled dose.

Contact your supplying pharmacy as soon as possible. Explain the storage issue and ask about a replacement. If you're concerned about what happens to a pen that has been affected by temperature, our page on frozen Wegovy explains the risks and next steps in detail. If you're a nume patient, our aftercare team is available seven days a week, you can reach us via the contact page. If storage in transit was the likely cause, your pharmacy will want to know.

Missing one dose is frustrating, but it is far preferable to injecting a medicine whose efficacy and safety can no longer be confirmed. Once you have a replacement pen and have resumed your normal schedule, you can track how the treatment is going on our page about signs that Wegovy is working. If the freeze appears to have occurred repeatedly or you're having consistent storage problems, let your prescriber know, they may review your overall plan with you. A private prescription through a clinician-led service means that kind of ongoing support is part of what you've paid for, not an extra.