Heatwave medication mistakes: a GP explains what to avoid

Did you know that some medications can make you more vulnerable to the effects of heat?

If not, you’re not alone. It’s an often-overlooked summer issue and many of us aren’t aware of the potential risks.

To help shed some light on the topic, the Medicines and Healthcare products Regulatory Agency (MHRA) recently issued a warning that certain medications can worsen heat-related effects such as dehydration, sunburn and dizziness. 

What’s more, hot conditions can also affect how certain medications work if they’re not stored properly.

There’s no need to panic, though. A few simple changes can help take the stress out of this common problem.

We asked Professor Azeem Majeed, of Imperial College, about the medication mistakes to be mindful of during a heatwave, and the steps you can take to store your medications safely when temperatures soar.

It’s important to note that this guide is for general wellness purposes only and you should not stop or alter prescribed medication yourself. For medical advice best suited to your needs and health conditions, speak with your pharmacist or GP.

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Professor Azeem Majeed is head of the department of primary care and public health at Imperial College London and an award-winning GP.

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How can hot weather affect your medicines?

‘High temperatures increase the risk of dehydration, which can alter how some medicines work and increase the likelihood of side effects,’ explains Professor Majeed.

For example, if you’re taking diuretics, you’ll be going to the toilet more often, thereby losing more fluid. Combined with increased sweating in hot weather, this can further fuel dehydration.

‘Heat can also change how the body absorbs, distributes and eliminates medications,’ he says. ‘In addition, some medicines interfere with the body's natural ability to regulate temperature or increase sensitivity to sunlight, making people more vulnerable during hot weather.’

Heat can also break down the active ingredients in medicines, so being careful about where and how you store them can be especially important during a hot spell.

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What medications make it hard to cope in the heat and why?

‘Several commonly prescribed medicines can increase vulnerability to hot weather,’ Majeed says.

They may increase your risk of dehydration, affect your body’s ability to cool down, make you more sensitive to sunburn or increase dizziness.

Scroll down to see a list of commonly used medications that could make you less tolerant to the heat. If you’re concerned, speak to your GP or pharmacist instead of stopping your medications yourself, as this can be dangerous. 

‘Pharmacists are an excellent source of advice,’ says Majeed. ‘They can review medications, explain potential heat-related effects and advise when medical review may be needed.’

Medicines that can increase your risk of dehydration

These include:

• Diuretics such as furosemide and bendroflumethiazide, which increase fluid loss.
• SGLT2 inhibitors used for diabetes (such as dapagliflozin and empagliflozin), which increase glucose and water loss through urine.
• Laxatives, particularly if overused.

Dehydration may also increase the risk of acute kidney injury in people taking blood pressure medicines such as ACE inhibitors.

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Medicines that can affect your body’s ability to cool down

Medicines that have anticholinergic properties block the action of acetylcholine, a chemical messenger involved in functions including sweating and bladder control. This can reduce the body's ability to sweat, making it harder to cool down.

Examples include:

• some antidepressants, particularly tricyclic antidepressants
• some antipsychotic medicines
• medicines used for an overactive bladder
• medicines used for Parkinson's disease

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Medicines that can make you more sensitive to the sun

Some medicines can cause photosensitivity, including:

• tetracycline antibiotics such as doxycycline
• retinoids
• disease-modifying anti-rheumatic drugs (DMARDs) such as methotrexate

Anyone who's taking these kinds of medicines should use sunscreen, wear protective clothing and avoid prolonged direct exposure to the sun. 

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Medicines that can increase dizziness

Heat can cause your blood vessels to dilate and lower your blood pressure. Some medicines can also lower blood pressure or affect the body's response to heat, potentially increasing the risk of dizziness or fainting.

These include:

• beta blockers 
• diuretics
• nitrates used for angina

Make sure you stand up slowly, stay well hydrated and seek medical advice if symptoms persist.

What steps can you take to minimise these risks?

A good starting point is to check the patient information leaflet of your medication, as it may contain advice about sun exposure and hydration. If you’ve lost it, you can also find it online on the MHRA products website.

Majeed offers these practical tips:

• Drink enough fluids unless you're advised otherwise by your healthcare professional.
• Stay out of direct sunlight during the hottest part of the day.
• Keep your home cool where possible.
• Wear lightweight clothing and use broad-spectrum sunscreen.
• Follow storage instructions carefully for your medicines.
• Be aware of symptoms such as dizziness, confusion, excessive thirst, reduced urination or fainting.
• Speak to a pharmacist if you’re concerned about your medicines during hot weather.

‘Most importantly, do not to stop prescribed medication without medical advice,’ cautions Majeed. 

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Top tips for storing your medications safely in hot weather

A heatwave can make it harder to store your medications safely; also storage requirements can vary between medicines. ‘Most medicines should be stored below 25°C, although some can be safely stored below 30°C,’ says Majeed. ‘Always check the packaging or patient information leaflet.’

He cautions not to leave any medicines in your car, conservatory or direct sunlight, where temperatures can rise very quickly, and says particular care is needed with:

• Insulin, which should be stored according to manufacturer guidance and protected from excessive heat
• Some biological medicines that require refrigeration
• Certain eye drops and liquid medicines
• Weight-loss injections.

Boots temporarily paused home delivery of weight-loss injections during the most recent heatwave.

This was because the retailer found that standard cold-chain packaging couldn’t reliably keep them within their required temperature range (below 8°C) during transit once outdoor temperatures exceeded 30°C. Collection for these medicines was recommended instead.

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According to the MHRA, it can be helpful to take the following steps to minimise the risk of the heat breaking down the active ingredients in your medications:

• Avoid leaving medicines that need to be kept in the fridge out for too long
• Keep your medicines in the coolest part of your house and out of direct sunlight
• Carry your medicines in a cool bag if you plan to take them outside with you.

Watch out for changes that could signal heat damage. These include changes to colour, smell or texture, and the overall look of your medications.

‘If medicines have been exposed to temperatures outside their recommended storage conditions, seek advice from your pharmacist before using them,’ advises Majeed.

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Who is more susceptible to heat-related issues?

While the effects of a heatwave can be felt by anyone, certain people should take extra care – with Majeed highlighting these groups:

• People taking multiple medications
• Older adults, particularly those aged 65 years and over. According to the British Dietetic Association, the usual signs of dehydration, such as thirst, urine colour and dry mouth become less reliable indicators with age
• Infants and young children
• People with long-term conditions such as heart or kidney disease, diabetes or respiratory illness
• People with severe mental illness
• Outdoor workers and those undertaking strenuous physical activity
• People who are socially isolated or unable to keep cool adequately.

If you're at increased risk of dehydration, it's important to drink regularly rather than relying on thirst alone, unless you've been advised to restrict your fluid intake.

Dehydration can lead to headaches, tiredness, confusion, lack of concentration, constipation and urinary tract infections.

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We make every effort to ensure our wellbeing reviews and advice are accurate, up to date and cover the key need-to-knows when buying. This information is for general wellness purposes only and is not a substitute for medical advice.