As the UK endures its third heatwave of 2026, with yellow and amber heat health alerts in force across most of the country, a pharmacist has issued urgent advice for anyone taking common medications including SSRIs (sertraline, citalopram, fluoxetine), hormonal contraception, insulin, blood pressure medication, ADHD stimulants, inhalers, and EpiPens.
SSRIs and Temperature Regulation
Jason Murphy, Head of Pharmacy at Chemist4U, explained that SSRIs are among the most widely prescribed medicines in the UK and can interfere with the hypothalamus, the part of the brain that regulates body temperature. This can lead to increased or decreased sweating, dizziness, and a reduced awareness of dehydration. “You may sweat more or less than usual, feel dizzy, or just not realise how dehydrated you’re getting until it catches up with you,” Murphy said.
Hormonal Contraception at Risk
Murphy also warned that hormonal contraception—including the combined pill, mini pill, patch, and vaginal ring—contains hormones sensitive to temperature. Most are designed to be stored below 25°C, and prolonged exposure above 30°C can degrade the hormones, reducing effectiveness. “A pill packet that’s spent a few days in a hot car, handbag, or beach bag… there’s a very real risk of unintended pregnancy,” he said. If pills appear discoloured, sticky, or softer than usual, Murphy advises treating them as compromised, starting a new pack, and using a backup method like condoms for at least seven days.
Other Affected Medications
Other medications affected by heat include SNRIs, tricyclic antidepressants, GLP-1 medications, diuretics, beta-blockers, ACE inhibitors, ARBs, ADHD stimulants, insulin, inhalers, and EpiPens. Heat can degrade active ingredients, alter absorption, or impair the body’s cooling mechanisms. Sun-sensitising medicines—such as some antibiotics, retinoids, diuretics, and antidepressants—can also cause skin to burn faster.
How to Stay Safe
Murphy offered several tips: Keep medicines stored below 25°C, avoid cars and sunny windowsills. Stay hydrated, especially if taking SSRIs, SNRIs, GLP-1 medications, or ADHD stimulants, which can blunt thirst. Avoid direct sunlight between 11am and 3pm, wear loose clothing, and use high-SPF sunscreen. Know the signs of heat exhaustion—headaches, dizziness, nausea, cramps, heavy sweating, or confusion—and act quickly. If symptoms persist for more than 30 minutes or worsen, call 999. “Never stop or change the dose of a prescription medication because of the weather without speaking to a healthcare professional first,” Murphy emphasised.
