Is Climate Change & Extreme Heat Reducing Drug Efficiency?

Climate change is intensifying the frequency and duration of heatwaves in the UK.

This environmental shift creates new risks for people who depend on temperature-sensitive medicines and medical devices.

The Medicines and Healthcare products Regulatory Agency (MHRA) warns that elevated temperatures can compromise pharmaceutical effectiveness and increase vulnerability to heat-related illness.

These concerns link directly to broader climate patterns that scientists say are driven by human activity.

Storage challenges during heatwaves

According to the UK Met Office, the Intergovernmental Panel on Climate Change (IPCC) concludes that human influence has warmed the atmosphere, oceans and land.

Average global land temperatures have increased by more than one degree Celsius since the Industrial Revolution.

This warming trend means medicine safety is no longer just a healthcare issue but an environmental one too.

According to the MHRA, many medicines should be stored below 25°C. Temperatures inside vehicles, bags, public transport and rooms with direct sunlight can exceed this threshold during warm weather.

Heat can break down active ingredients in pharmaceuticals. This degradation could reduce treatment effectiveness across tablets, inhalers, hormone patches, insulin and EpiPens.

Refrigerated medicines face particular vulnerability. Insulin and some liquid antibiotics require consistent cold storage.

The MHRA advises checking storage instructions in patient information leaflets. People should keep medicines in the coolest part of their home and avoid leaving them in parked vehicles or warm bags.

Medical devices and temperature

Blood glucose monitors used by people managing diabetes may produce less reliable readings if stored or used in hot conditions, according to the MHRA. Device accuracy could decline as temperatures rise.

Medical technology designed for temperate climates faces performance issues during extreme heat. This challenge will likely increase as climate projections suggest hotter summers.

Sustainability leaders won’t want to miss Sustainability LIVE: The Leadership Summit at London Climate Action Week, taking place at Code Node on 25 June 2026.

Register now for this exclusive invite-only event. 

The Met Office states that the UK's 10 warmest years since 1884 have all occurred since 2002. Warm spells have more than doubled in average length compared with previous decades.

By the end of the century, temperatures of 40°C could occur every three to four years under a high emissions scenario, according to Met Office climate projections.

How medicines interact with heat

Hot weather can alter how the body responds to medicines and increase dehydration risk, the MHRA warns. Certain medications amplify these effects.

"Let's face it – when there's a heatwave, most of us are focused on getting outside and enjoying it while it lasts. But it's easy to forget that medicines left in the heat – in cars, bags or on sunny windowsills – might not work properly when you need them," says Alison Cave, Chief Safety Officer at the MHRA.

"Some medicines can also make you more likely to burn in the sun, feel dizzy or get dehydrated, especially if you're taking diuretics or have a condition like asthma, heart disease or diabetes."

Alison continues: "To stay safe in the heat: Store medicines somewhere cool, dry and out of direct sunlight – especially if you're out and about. Know the signs of heat-related illness – stay hydrated and listen to your body. Take extra care in the sun if your medicine makes your skin more likely to burn. And remember, for all medicines it's important to read the leaflet and speak to a healthcare professional if you have any questions."

People taking diuretics lose additional fluid through urination. Some blood pressure medicines can make it harder for the body to regulate temperature during hot spells.

Certain diabetes medicines, including insulin and metformin, can also increase dehydration risks.

These medications could make early warning signs more difficult to recognise.

Other medications, including some antipsychotics and stimulant medicines used for attention disorders, may raise body temperature. This effect could increase the likelihood of overheating.

Symptoms of dehydration can include dizziness, headaches, tiredness, confusion and dark urine.

According to the MHRA, older adults, young children and people with heart or kidney conditions may face greater risks during periods of extreme heat.

Some commonly used medicines can make the skin more sensitive to sunlight. The MHRA highlights that certain antibiotics, diuretics, antidepressants and treatments for acne or eczema can increase sunburn risk.

Methotrexate requires particular caution. This medicine is used to treat conditions including rheumatoid arthritis, psoriasis, Crohn's disease and cancer.

It can cause severe skin reactions following sun exposure. These risks become more significant as people spend more time outdoors during warm weather.

The MHRA advises patients to read medicine leaflets carefully. People should consult healthcare professionals if they are unsure whether their medication increases sun sensitivity.

Climate science and health impacts

The World Meteorological Organization (WMO), citing the IPCC Sixth Assessment Report, reports that human-caused climate change has increased the frequency and intensity of heatwaves since the 1950s.

Additional warming will further increase these extremes.

The WMO also notes that increasing temperatures and heatwaves have already contributed to higher rates of illness and death. Impacts are particularly severe among vulnerable populations.

Climate projections suggest hotter and drier summers will become increasingly common in the UK.

This environmental trajectory means pharmaceutical storage and heat health awareness are now climate adaptation issues.

Medicine safety protocols designed for cooler climates may need revision.

The intersection of healthcare and environmental change creates new challenges for public health systems in a warming world.