Weight loss injections containing GLP-1 receptor agonists, such as semaglutide (Wegovy), must be refrigerated to maintain their stability and therapeutic effectiveness. These biological medications contain delicate peptide molecules that degrade when exposed to inappropriate temperatures. Unopened pens require storage at 2°C to 8°C, whilst in-use pens may be kept at room temperature below 30°C for limited periods. Freezing causes irreversible damage, rendering the medication ineffective. Understanding proper storage requirements is essential for patients prescribed these treatments, as improper handling compromises clinical outcomes and represents both a safety concern and waste of NHS resources. This article provides comprehensive guidance on refrigeration requirements, storage protocols, and practical advice for maintaining medication integrity.
Quick Answer: Yes, weight loss injections containing GLP-1 receptor agonists must be refrigerated at 2°C to 8°C when unopened to maintain their stability and therapeutic efficacy.
Weight loss injections, particularly the newer generation of GLP-1 receptor agonists such as semaglutide (Wegovy) and tirzepatide (Mounjaro), require refrigeration to maintain their stability and therapeutic efficacy. These medications are biological products containing peptide molecules that are sensitive to temperature fluctuations and environmental conditions. Storage requirements are specified in the Summary of Product Characteristics (SmPC) and Patient Information Leaflet (PIL) approved by the Medicines and Healthcare products Regulatory Agency (MHRA).
Unopened pens must be stored in a refrigerator at temperatures between 2°C and 8°C. This temperature range is critical for preserving the molecular structure of the active pharmaceutical ingredient. Storage requirements after first use vary by product:
Wegovy (semaglutide): Single-use pens that may be kept at room temperature (up to 30°C) for up to 28 days before use
Mounjaro (tirzepatide): Single-use pens that may be kept at room temperature (up to 30°C) for up to 14 days before use
Ozempic (semaglutide): Multi-dose pens that can be stored at room temperature (up to 30°C) for up to 6 weeks after first use
Saxenda (liraglutide): Multi-dose pens that can be stored at room temperature (up to 30°C) for up to 30 days after first use
It is essential to never freeze these medications. Freezing causes irreversible damage to the peptide structure, rendering the medication ineffective and potentially unsafe. If a pen has been frozen, it must be discarded immediately, even if it subsequently thaws. Additionally, these injections should be protected from direct sunlight and excessive heat, and the pen cap should remain on when not in use to shield the medication from light exposure.
Patients prescribed weight loss injections should receive clear written instructions regarding storage requirements at the point of dispensing. Community pharmacists play a vital role in counselling patients about proper storage, and healthcare professionals should confirm that patients can meet the storage requirements before initiating treatment.
GLP-1 receptor agonists are peptide-based biological medications with complex molecular structures that are inherently unstable at elevated temperatures. Unlike small-molecule drugs that may tolerate ambient conditions, these large protein molecules undergo conformational changes when exposed to heat, leading to degradation, aggregation, or denaturation. Such structural alterations compromise the medication's ability to bind effectively to GLP-1 receptors, thereby reducing therapeutic efficacy.
The mechanism of action of semaglutide and tirzepatide relies on their precise three-dimensional structure to mimic endogenous GLP-1 and, in the case of tirzepatide, glucose-dependent insulinotropic polypeptide (GIP). These medications work by enhancing insulin secretion in a glucose-dependent manner, suppressing glucagon release, slowing gastric emptying, and promoting satiety through central nervous system pathways. Any degradation of the peptide structure interferes with receptor binding affinity and duration of action, potentially resulting in suboptimal glycaemic control and reduced weight loss efficacy.
Refrigeration slows the rate of chemical and physical degradation processes, including:
Hydrolysis – the breakdown of peptide bonds in the presence of water
Oxidation – damage to amino acid residues, particularly methionine and cysteine
Aggregation – the clumping of protein molecules, which may potentially trigger immune responses
Deamidation – chemical modification of asparagine and glutamine residues
Clinical studies supporting the licensing of these medications were conducted using properly stored products. Using degraded medication risks treatment failure and may potentially affect the medication's safety profile. The stability data supporting storage recommendations are detailed in the European Public Assessment Reports (EPARs) and MHRA Public Assessment Reports (PARs). The storage conditions specified in the SmPC are based on comprehensive stability testing conducted by manufacturers and reviewed by regulatory authorities.
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Start HereSemaglutide (Wegovy) should be stored unopened in a refrigerator at 2°C to 8°C until the expiry date printed on the label. According to the UK SmPC, Wegovy pens are single-use devices that may be stored at temperatures up to 30°C for up to 28 days before use. The pen should be kept with the cap on to protect it from light. It must never be stored in the freezer or freezer compartment, and if accidentally frozen, the pen must be discarded.
Tirzepatide (Mounjaro) follows similar but slightly different guidelines. Unopened pens should be refrigerated at 2°C to 8°C. Mounjaro pens are also single-use devices and may be kept at temperatures up to 30°C for up to 14 days before use. Like semaglutide, tirzepatide must never be frozen, and frozen pens cannot be used even after thawing. The pen cap should remain on to protect the medication from light.
For multi-dose pens such as Ozempic (semaglutide) and Saxenda (liraglutide), different in-use storage periods apply. Ozempic can be stored at temperatures up to 30°C for up to 6 weeks after first use, while Saxenda can be stored at temperatures up to 30°C for up to 30 days after first use.
For all these medications, patients should:
Store pens in the original carton to protect from light
Keep pens in the main body of the refrigerator, not in the door where temperature fluctuates
Avoid placing pens near the freezer compartment or cooling elements
Allow the pen to reach room temperature before injecting (approximately 30 minutes) to reduce injection site discomfort
For multi-dose pens only: Never store with the needle attached, as this can cause leakage or air bubbles
For multi-dose pens only: Record the date of first use on the pen label
Check the solution before each use – it should be clear and colourless to slightly yellow
Patients should always consult the patient information leaflet supplied with their specific product, as formulations and storage requirements may vary between brands and presentations. When in doubt, pharmacists or prescribers should be contacted for clarification.
When weight loss injections are stored outside the recommended temperature range, the peptide molecules begin to degrade at an accelerated rate. The extent of degradation depends on both the temperature and the duration of exposure. Brief exposure to room temperature during transport or administration is generally acceptable, but prolonged storage at elevated temperatures compromises the medication's integrity.
If an unopened pen has been left at room temperature (below 30°C), the acceptable duration varies by product according to the UK SmPC:
Wegovy (semaglutide): Up to 28 days
Mounjaro (tirzepatide): Up to 14 days
Ozempic (semaglutide): Up to 8 weeks (including in-use period)
Saxenda (liraglutide): Up to 30 days
However, if the pen has been exposed to temperatures above 30°C or left unrefrigerated for longer than the SmPC-permitted duration, the medication should be considered compromised. There is no reliable way for patients to assess whether degradation has occurred, as the solution may appear unchanged even when the active ingredient has lost potency.
Using degraded medication poses several risks:
Reduced efficacy – inadequate glycaemic control and diminished weight loss
Unpredictable dosing – variable amounts of active ingredient may remain
Potential for altered safety profile – degraded products may behave differently
Treatment failure – patients may not achieve therapeutic goals
Wasted resources – ineffective medication represents both clinical and financial loss
Patients who suspect their medication has been improperly stored should not use it. They should contact their prescriber or pharmacist for guidance and obtain a replacement if necessary. The primary concern with improperly stored GLP-1 medications is loss of therapeutic effect rather than direct toxicity. However, continuing treatment with ineffective medication delays appropriate management and may lead to disease progression.
If you experience any side effects or suspect a reaction to these medicines, report it via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk) and seek advice from a healthcare professional.
Travelling with weight loss injections requires advance planning to maintain proper storage conditions throughout the journey. For short trips (day trips or overnight stays), a pen stored at room temperature within its SmPC-permitted duration can be carried safely in hand luggage, provided it remains below 30°C and is protected from direct sunlight. The pen should be kept in its original carton and placed in a cool, shaded part of the luggage.
For longer journeys or when carrying unopened pens, a cool bag or medical travel case with ice packs is essential. Purpose-designed medication cooling wallets are available from pharmacies and maintain temperatures between 2°C and 8°C for several hours. When using ice packs:
Ensure the medication does not come into direct contact with ice or frozen gel packs, as this may cause freezing
Use an insulating barrier (such as a cloth or the medication carton) between the ice pack and the pen
Replace ice packs as needed during extended travel
Monitor the temperature if possible using a small thermometer
When travelling by air, weight loss injections should be carried in hand luggage rather than checked baggage, as hold temperatures can drop below freezing. According to UK Department for Transport and Civil Aviation Authority guidance, patients should carry:
Medicines in their original packaging with dispensing labels
A copy of their prescription or a letter from their prescriber confirming the medical necessity of the medication and syringes/needles
Declare medicines and needles at security screening points
Upon reaching the destination, medications should be refrigerated as soon as possible. When staying in hotels, patients should:
Request a room with a refrigerator or use of a medical refrigerator at reception
Avoid using mini-bar fridges that may freeze items
Never leave medications in hot cars or direct sunlight
Consider portable medication coolers for destinations without reliable refrigeration
For international travel, patients should research storage options in advance and consider the climate of their destination when planning medication supply. The NHS website provides additional guidance on travelling with medicines.
Patients should immediately discard weight loss injections in the following circumstances:
The medication has been frozen at any point, even if subsequently thawed
An unopened pen has been stored above 30°C for any period
An unopened pen has been left at room temperature (below 30°C) for longer than the SmPC-permitted duration:
Saxenda (liraglutide): More than 30 days
For multi-dose pens (Ozempic, Saxenda): The in-use period has been exceeded
The solution appears cloudy, discoloured, or contains particles (it should be clear and colourless to slightly yellow)
The pen has been damaged or dropped, potentially affecting the mechanism
The expiry date has passed
There is any doubt about storage history or integrity
Visual inspection before each injection is crucial. Patients should hold the pen up to the light and examine the solution carefully. Any cloudiness, colour change, or visible particles indicates degradation or contamination, and the pen must not be used. However, it is important to note that degradation may occur without visible changes, so storage history remains the primary determinant of usability.
When discarding medication, patients should follow local guidelines for pharmaceutical waste disposal. Used pens and needles should be placed in a sharps container, which can typically be obtained from GP surgeries or pharmacies. Full sharps containers should be returned according to local council or NHS-commissioned sharps disposal services – they must never be disposed of in household waste or recycling bins.
If medication must be discarded due to improper storage, patients should contact their prescriber or pharmacy promptly to obtain a replacement. Replacement policies may vary locally, so proper storage is both a clinical and financial imperative. Patients experiencing difficulties with storage should discuss alternative treatment options with their healthcare provider, as adherence to storage requirements is essential for treatment success.
In-use pens may be carried at room temperature below 30°C for short trips, but unopened pens require a medical cool bag with ice packs. Always carry injections in hand luggage and ensure they don't come into direct contact with ice to prevent freezing.
Contact your pharmacist or prescriber for advice. If an in-use pen has been at room temperature within the permitted timeframe (6 weeks for semaglutide, 30 days for tirzepatide) and below 30°C, it may still be usable, but professional guidance is essential.
Freezing causes irreversible damage to the peptide structure of GLP-1 medications, destroying their ability to bind to receptors and rendering them therapeutically ineffective. Frozen pens must be discarded immediately, even after thawing.
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DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
