The Met Office has issued a rare amber heat warning for Monday to Thursday across parts of Wales and South England, affecting millions of people who take beta blockers or metformin. These two commonly prescribed medications can increase dehydration risk, interfere with temperature control, or hide warning signs of heat-related conditions.
How Beta Blockers Affect Heat Regulation
The British Heart Foundation states that beta blockers are among the most widely prescribed treatments for heart and circulatory problems, frequently used to treat irregular heart rhythms, angina and high blood pressure. By slowing the heart rate, this medicine can hinder the body's natural cooling systems, making users considerably more vulnerable to overheating.
The Medicines and Healthcare products Regulatory Agency (MHRA) has warned: "Blood pressure medicines such as ACE inhibitors, beta-blockers, or calcium channel blockers can also make it harder for your body to regulate temperature, especially during sudden hot spells."
Research from 2022 also found that people on beta blockers or antiplatelet medication could be at greater risk of heart attacks during hot weather than in cooler conditions. Beta blockers specifically demonstrated a 65% stronger association between high temperatures and heart problems.
Metformin and Dehydration Risks
Metformin, insulin and other diabetic medications can increase your susceptibility to dehydration while masking the early warning signs. If left untreated, dehydration can lead to worsening symptoms and in extreme cases may cause kidney and urinary problems, seizures or even damage to the brain.
Important symptoms of dehydration include feeling thirsty, headache and feeling light-headed, dark yellow strong-smelling urine, peeing less often than usual, feeling dizzy or lightheaded, feeling tired, a dry mouth, lips and tongue, and sunken eyes.
Precautions for Medication Users
Dehydration can be simple to treat by drinking fluids or using oral rehydration solutions bought from pharmacists. People taking beta blockers or metformin should not stop their medication just because it is getting warmer. However, they need to act quickly if they start noticing any signs of dehydration or symptoms related to heat illness.
Those aged over 75 already face heightened susceptibility to temperature-related ailments including heat stroke, heat exhaustion and dehydration. Family members are encouraged to keep a close eye on their elderly relatives during spells of hot weather, especially if they are on these medications.
The MHRA has recommended that anyone on medication should check their patient information leaflet or speak with their pharmacist to verify whether sun sensitivity is noted as a possible side effect.
Amber Heat Warning Details
The Met Office has issued a rare amber warning for extreme heat, in force from 1am on Monday 22 June until 23:59pm on Thursday 25 June. It represents the most serious heat warning the Met Office has released in four years, with the last one having been issued in August 2022.
Officials have cautioned of a "widespread impact" on both the public and infrastructure, warning that some employees may need to modify their working patterns during this spell. The warning additionally notes: "The wider population are likely to experience some adverse health effects including sunburn or heat exhaustion and other heat related illnesses."
