With temperatures soaring across parts of the UK this summer, many people remember to pack water bottles, sunglasses, and sunscreen before setting off on a journey. One essential item, however, is often overlooked in hot weather: medication.
Many medicines are designed to be stored within a specific temperature range, yet the inside of a parked car can become far hotter than the air outside. Studies show that a vehicle’s interior temperature can rise by up to 50% within an hour on a warm day, even when outside temperatures are not extreme. Much of this increase occurs within the first 30–60 minutes, according to research on vehicle cabin temperatures.
According to motoring experts at Dick Lovett, leaving medication in a hot car during a heatwave could have serious consequences.
Alex Lee, motoring expert at Dick Lovett, said: “It is really important to understand what happens if you leave medicine in a hot car, especially if you rely on life-saving medication. Prescriptions such as insulin, antibiotics, and inhalers often have strict storage guidelines. If they are not stored at the correct temperature, they can lose their effectiveness or break down chemically. Heat exposure may also damage adrenaline auto-injectors such as EpiPens, potentially affecting how well they work. Always carry your medication with you, ideally in a small insulated pouch, and never leave it in a parked car.”
The Medicines and Healthcare products Regulatory Agency (MHRA) advises that many medicines should be stored below 25°C, warning that exposure to higher temperatures can reduce their effectiveness. Its guidance states that heat can affect medicines including tablets, inhalers, hormone patches, insulin, and adrenaline auto-injectors such as EpiPens, potentially reducing how well they work when needed. Medication may appear unchanged after being left in a hot vehicle, even if heat has affected its stability, making it difficult to tell whether it has been compromised.
This is particularly important for people managing long-term conditions such as diabetes or asthma, where reliable medication is essential. During recent heatwaves, the MHRA has also highlighted that temperature-sensitive medicines, including insulin and some liquid antibiotics, require extra care to ensure they are stored within the recommended temperature range.
Planning ahead can help protect both your medication and your health during hot weather. Useful precautions include
- Keeping medication in a small insulated pouch.
- Taking it with you whenever you leave the car.
- Checking the storage instructions on the packaging.
- Speaking to a pharmacist if you are unsure whether it has been exposed to excessive heat.
Medication is not the only item that can be affected by high temperatures inside a parked car. Dick Lovett also advises against leaving electronics, power banks, aerosol cans, fizzy drinks, sunscreen, cosmetics, plastic water bottles, important documents, and prescription glasses in a vehicle, as prolonged heat can cause many of these items to leak, deteriorate, or, in some cases, pose a fire or explosion risk.
The safest approach is to treat a parked car like any other enclosed space during extreme heat. Before locking the vehicle, remove anything that could be damaged by high temperatures, park in the shade where possible, use a reflective windscreen sunshade, and keep essential items in insulated bags.
As periods of extreme heat become more frequent in the UK, taking a few extra moments to consider what is left inside a parked car could help protect not only personal belongings, but health as well.