Doctors warn that extreme heat can change how some prescription medications work and increase the risk of dangerous side effects.
Common drugs for high blood pressure, heart disease, mental health conditions, and allergies may make it harder for the body to stay cool or stay hydrated.
Experts say patients should never stop taking medications on their own but should talk with their healthcare provider or pharmacist if they have concerns during a heat wave.
As much of the United States faces another stretch of dangerous summer heat, doctors are warning that soaring temperatures don't just pose a threat on their own — they can also change how some prescription medications affect the body.
Health experts say certain medications can interfere with the body's ability to regulate temperature, increase dehydration, reduce sweating, or become less effective if they are exposed to excessive heat. Older adults and people with chronic health conditions are especially vulnerable.
"Medications and heat can interact, leading to potentially severe side effects," the Centers for Disease Control and Prevention (CDC) says in guidance issued for clinicians. The agency notes that healthcare providers should help patients understand which medications may increase their risk during periods of extreme heat.
Which medications are affected?
According to the CDC, medications that may increase the risk of heat-related illness include:
Diuretics ("water pills"), which can contribute to dehydration.
ACE inhibitors and angiotensin receptor blockers (ARBs), commonly prescribed for high blood pressure and heart disease.
Anticholinergic medications, used to treat conditions ranging from overactive bladder to allergies and Parkinson's disease, which can reduce sweating.
Some antidepressants, antipsychotics, and other psychiatric medications, which may interfere with the body's ability to regulate temperature.
Certain over-the-counter medications, particularly when combined with prescription drugs.
Some antibiotics, acne medications, and anti-inflammatory drugs can also make skin much more sensitive to sunlight, increasing the risk of severe sunburn during prolonged outdoor exposure.
Heat can affect the medicine itself
High temperatures don't just affect the person taking the medication — they can also damage the medication.
Pharmacists warn that medicines left in hot cars, direct sunlight, or other excessively warm places may lose potency. Drugs that require refrigeration, such as insulin, are especially susceptible to heat damage.
The CDC also advises patients to have a plan for refrigerated medications in case power outages occur during extreme weather.
What patients should do
Doctors stress that people should not stop taking prescribed medications simply because temperatures are high.
Instead, they offer the following advice:
Talk with your doctor or pharmacist if you're taking medications that could increase heat sensitivity.
Stay well hydrated unless you've been instructed to limit fluids.
Store medications according to the manufacturer's instructions, keeping them out of hot vehicles and direct sunlight.
Spend as much time as possible in air-conditioned spaces during extreme heat.
Watch for warning signs such as dizziness, confusion, excessive fatigue, rapid heartbeat, or an inability to sweat, and seek medical attention if symptoms become severe.
The CDC emphasizes that patients should never discontinue or adjust medications without consulting a healthcare professional, since doing so could pose greater health risks than the heat itself.