What hot weather can do to your medicines, how to store them safely at home and on the move, and when it is best to ask a pharmacist.
You know that feeling when you open a parked car on a hot day, and the air hits you like an oven?
Now imagine your medication sitting inside that heat for hours.
We often think about keeping ourselves cool when temperatures rise, but the medicines we rely on need protection from extreme temperatures too. Heat can affect the stability of some medicines, reducing how well they work. In certain situations, very high temperatures can also damage the medicine’s packaging or the device used to deliver it.
That does not mean every tablet accidentally left in a warm room is suddenly unsafe. Medicines differ, and so do their storage requirements. How much damage occurs depends on the medicine itself, the temperature it reached, and how long it was exposed.
The important thing is knowing what your medicine needs — and what to do when you are unsure.
So, can heat make medication less effective?
Yes. Excessive heat can cause some medicines to break down more quickly, which means they may lose some of their effectiveness before the expiry date printed on the packaging.
Many medicines are designed to be stored somewhere cool and dry. However, there is no single temperature rule that applies to every medicine.
The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) advises that many medicines need to be stored below 25°C (77°F), while others have their own specific temperature requirements.
So rather than trying to remember one magic number, check the storage instructions on the box, label or patient information leaflet.
This becomes particularly important during heatwaves, long journeys, holidays and power cuts, when medicines can spend several hours somewhere much warmer than you realise.
Which medicines need extra care in hot weather?
Some medicines are especially sensitive to changes in temperature.
Insulin is one important example. Many unopened insulin products are normally kept refrigerated, while some can be stored at room temperature for a limited time once they are being used. Exactly how long and at what temperature depends on the individual product.
The US Food and Drug Administration’s insulin storage guidance notes that extreme temperatures can reduce insulin’s effectiveness. Freezing can damage insulin too.
Other products may also need particular care, including certain liquid antibiotics, injections, creams, inhalers and emergency medicines.
Extreme heat may even affect some medication delivery devices. The CDC warns, for example, that some inhalers can malfunction or burst in very hot environments, while heat exposure may interfere with some adrenaline (epinephrine) auto-injectors, such as EpiPens.
You do not need to memorise a huge list of heat-sensitive medicines. What matters is knowing the storage instructions for the medicines you use, particularly anything you depend on in an emergency or to manage a long-term condition.
The hot-car problem
A handbag on the passenger seat may seem like a perfectly ordinary place to keep medication.
So might the glove box.
Or the boot.
The problem is that a parked vehicle can become extremely hot, and direct sunlight can make matters worse.
Both the MHRA and US health authorities advise against leaving medicines in hot vehicles. Even a medicine that normally sits happily in your handbag may be exposed to temperatures well beyond its recommended storage range when that bag is left inside a parked car.
If you carry an emergency medicine every day, it helps to make taking it out of the car part of your routine — just like remembering your phone, keys or wallet.
“Only for a few minutes” has an unfortunate habit of becoming much longer.
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How do you carry temperature-sensitive medication without freezing it?
This is where it is easy to swap one temperature problem for another.
If a medicine needs to stay cool while you are travelling, an insulated medication bag or cool bag can be helpful.
But colder does not automatically mean safer.
Some medicines can be damaged by freezing, so placing them directly against an ice pack or frozen gel pack may create another problem.
The CDC recommends keeping insulin and other diabetes medicines cool when travelling but specifically advises against placing insulin directly on ice or a gel pack.
A practical approach is to:
- keep the medicine in its original packaging where possible
- place a cloth, pouch or other barrier between the medicine and the frozen pack
- use an insulated medication bag with separate compartments
- keep the medicine away from direct sunlight
- check the manufacturer’s storage instructions before travelling.
For a long journey, flight, camping trip, festival or holiday in a very hot climate, speak to a pharmacist beforehand if you are unsure how your particular medicine should be transported.
Temperature-sensitive medicines do not all have the same requirements.
Where should you store medicines at home?
The bathroom cabinet may be convenient, but it is not always the best home for your medicine.
Every shower or bath can fill the room with warmth and moisture. Over time, that may affect some medicines.
For many medicines, a better place is somewhere cool, dry and away from direct sunlight and obvious sources of heat.
Depending on your home, that might mean a bedroom drawer, locked cupboard or medication box away from radiators, cookers, sinks and sunny windows.
MedlinePlus recommends storing medicines in a cool, dry location and notes that heat, air, light and moisture can damage them.
And if your medicine normally needs refrigeration, follow the instructions for that particular product.
Do not automatically move every medicine into the fridge simply because the weather is hot. Some products are designed to be stored at room temperature, and refrigeration may not be appropriate.
How can you tell if heat has damaged your medicine?
Sometimes the medicine will tell you something is wrong.
Look for changes such as:
- tablets or capsules sticking together
- cracked or chipped tablets
- unusual softness or hardness
- a change in colour
- an unusual smell
- changes in texture
- creams that have separated
- liquids that suddenly look different.
MedlinePlus advises against using medicines that have noticeably changed in colour, texture or smell.
But there is an important catch.
A heat-damaged medicine may still look completely normal.
You cannot reliably judge its potency simply by looking at it.
If you know that an important medicine has been left somewhere unusually hot — particularly insulin, an injection, an emergency medicine or medication used to control a serious condition — check its storage information and ask a pharmacist, prescriber or manufacturer for advice.
Do not double a dose, change your treatment or abruptly stop a prescribed medicine because you are worried about heat damage without first getting appropriate professional advice.
A small summer habit that can protect your health
Medication storage is easy to forget because nothing dramatic happens when you put a medicine into your bag.
It simply sits there.
And on an ordinary day, that is usually fine.
But when temperatures climb, try asking yourself one simple question before you leave home:
Where will my medicine be for the next few hours?
Not just where it is now.
Where will it be when you stop for lunch? When the bag is sitting beside you at the beach? When you park the car? When you are halfway through a long train journey?
Keep medicines away from direct sunlight and hot vehicles. Use appropriate insulated storage when the product requires it, without allowing medicines that should not freeze to sit directly against ice.
And if you are ever unsure whether heat has affected an important medicine, ask a pharmacist rather than guessing.
Your medicines have an important job to do.
Storing them properly gives them the best chance of doing that job when you need them most.
Medical disclaimer
This article is for general health information and does not replace individual advice from your doctor, pharmacist or other qualified healthcare professional.
