Medications that raise your risk in a heat wave: what the CDC and the drug labels say

Short answer: The CDC’s list of commonly prescribed medications that increase risk from heat starts with diuretics, anticholinergic drugs and some psychiatric medications, and it warns that combinations such as an ACE inhibitor or ARB with a diuretic may significantly increase the risk. Medicines do it in different ways: less thirst, less sweating, more fluid loss, lower blood pressure, or a drug building up when you are dehydrated. Do not stop a medicine on your own; the CDC tells clinicians to remind patients not to stop abruptly, and to make a plan for hot days instead.

In September 2025 the CDC published Heat and Medications: Guidance for Clinicians. It is written for doctors and pharmacists, but the substance is useful to anyone who takes a daily medicine and lives somewhere that gets heat waves.

This guide sets out what it says in plain terms, what the FDA labels themselves say about heat (from our medication heat-warning label index of 83 medicines), and the questions to take to your prescriber or pharmacist before summer. To look up your own medicines, use our medication and heat checker.

This is general information, not medical advice. The point of it is a better conversation with whoever prescribes for you, not a change you make on your own.

How medicines raise heat risk: the CDC’s eight ways

The CDC lists eight ways a medicine can make heat more dangerous, with examples of each.

1. Less thirst. Diuretics, ACE inhibitors and ARBs.
2. Interference with the body’s temperature control. Antipsychotics, anticholinergic drugs and stimulants.
3. Changes in sweating. More sweating with SSRIs and SNRIs; less with tricyclic antidepressants, antipsychotics and anticholinergic drugs, which means less cooling.
4. Fluid loss and low blood pressure, with a higher risk of fainting and falls, partly through reduced blood flow to the kidneys or kidney injury. Examples include NSAIDs, diuretics, beta blockers, tricyclic antidepressants and laxatives.
5. Less widening of the blood vessels in the skin, so heat is harder to shed. Aspirin, beta blockers and clopidogrel.
6. A drug building up when you are dehydrated, especially drugs with a narrow margin between a working dose and a toxic one. Apixaban, carbamazepine and lithium.
7. Electrolyte imbalance. Diuretics, beta blockers, calcium channel blockers, antacids, laxatives, lithium and trimethoprim-sulfamethoxazole.
8. Sedation or slowed thinking, with more falls and less thirst. Opiates, benzodiazepines, antipsychotics, antidepressants and anticonvulsants.

Two points in the guidance are easy to miss. Combinations add up: an ACE inhibitor or ARB taken with a diuretic “may significantly increase risk of harm from heat exposure,” and the newer ARNI drugs such as sacubitril/valsartan may carry the same added risk. And over-the-counter medicines count: the CDC’s table includes sedating antihistamines such as diphenhydramine and doxylamine, NSAIDs, aspirin, and acetaminophen, for which it notes that heat-related liver injury increases the risk of liver damage.

Children and teens

The CDC names its own list for young people: non-selective antihistamines such as diphenhydramine, stimulants such as methylphenidate for ADHD, tricyclic antidepressants, SSRIs and diuretics. Our guides to ADHD stimulants and antihistamines cover what their labels say.

What the FDA labels themselves say

Our label index reads the FDA label of 83 commonly used medicines for heat, sweating, dehydration and sun wording. Of the 83, 24 labels mention heat or the body’s temperature control:

• Less sweating, more risk of overheating (9 labels): topiramate (Topamax, Qsymia), zonisamide (Zonisade) and anticholinergic drugs such as oxybutynin, benztropine, glycopyrrolate, hyoscyamine, solifenacin and the scopolamine patch.
• Body temperature regulation (5): the antipsychotics Abilify, Risperdal, Zyprexa, Seroquel and Seroquel XR.
• Heat and patches or devices (6): fentanyl, buprenorphine and methylphenidate patches, two hormone patches, and insulin.
• Hot weather named as a risk (3): amitriptyline, lithium and hydrochlorothiazide.
• Heat intolerance as a sign of too much thyroid hormone (1): Synthroid.

Ten labels use the words hot weather outright. The Medication Guides for Abilify, Seroquel and Seroquel XR all say: “In hot weather, stay inside in a cool place if possible.” The lithium Medication Guide says “Avoid becoming overheated or dehydrated during exercise and in hot weather.” The topiramate, Qsymia, zonisamide and benztropine labels warn about decreased sweating or overheating in hot weather, the hydrochlorothiazide label warns that low sodium “may occur in edematous patients in hot weather,” and the amitriptyline label reports a very high fever when it is taken with anticholinergic or antipsychotic drugs, “particularly during hot weather.”

Why a label check is not enough

Many drugs on the CDC’s list carry no heat warning on their FDA label at all. The propranolol label in our index has no heat, sweating or dehydration wording, though the CDC lists beta blockers for reduced skin blood flow and sweating. The Benadryl label uses none of the terms we searched for, though the CDC lists diphenhydramine for decreased sweating. SSRI labels list sweating as a common side effect without a heat warning.

So the label tells you what the manufacturer was required to warn about, and the CDC list tells you how the drug class behaves in heat. You need both, and your pharmacist has both.

Heat and how medicines are stored

Heat can damage the medicine itself. The CDC notes that inhalers can burst in hot places such as a car trunk, that EpiPens may malfunction or deliver less epinephrine after heat exposure, and that insulin, which should be refrigerated, may become less effective if left in the heat for long. Its advice to clinicians is to counsel patients not to leave medicines in a car or other places that get very hot, and to plan for medicines that need a fridge during a power outage.

Our guides to insulin pumps and CGMs in heat and medicated patches cover the device side.

Medicines that make you burn faster

Some medicines raise sun sensitivity rather than heat risk. The CDC names antifungals such as flucytosine, griseofulvin and voriconazole, and antibiotics such as metronidazole, tetracyclines and fluoroquinolones, and recommends sun avoidance, protective clothing and broad-spectrum sunscreen of SPF 30 or higher. Our guide to doxycycline and antibiotics covers the label wording.

What to do before and during a heat wave

These steps follow the CDC’s guidance to clinicians, turned around into what you can ask for.

• Ask for a medication review before summer. The CDC asks clinicians to review medication lists with patients, especially older patients who take several medicines that raise heat risk in different ways.
• Ask for a plan for hot days. The CDC suggests making a plan for medication management on HeatRisk orange, red and magenta days, the higher levels of the HeatRisk heat forecast, and for when to seek medical care. If you have been told to limit fluids, ask whether that changes on hot days.
• Do not stop a medicine on your own. The CDC’s guidance is to “remind patients to avoid abruptly stopping any medications without having a plan in place.” Any change belongs to your prescriber.
• Keep medicines out of hot cars and plan for a power outage if anything needs a fridge.
• Stay somewhere cool, and have someone check on you, which the CDC recommends especially for older people and anyone whose thinking is affected.

Signs of heat illness and when to call 911

MedlinePlus describes heat illness in stages. Early signs are muscle cramps, fatigue, thirst and very heavy sweating. Heat exhaustion adds cool, moist skin, severe thirst, dark urine, dizziness, headache, nausea or vomiting, weakness and a rapid, weak pulse.

Heat stroke is the emergency: a very high body temperature with confusion, irrational behavior, seizures, slurred speech, extreme lethargy or unconsciousness, and sweating may stop. MedlinePlus says to call 911 if the person loses consciousness, has any change in alertness, has a fever over 102°F (38.9°C) or other signs of heatstroke, or does not improve.

One medicine point belongs here too: MedlinePlus says not to give someone with heat illness fever medicines such as aspirin or acetaminophen, because they will not help and may be harmful.

Medicines and heat at a glance

Drug class (CDC examples)	How the CDC says it raises heat risk	What the FDA label in our index says
Diuretics (furosemide, hydrochlorothiazide)	Fluid loss, electrolytes, less thirst, fainting	Hydrochlorothiazide names hot weather; Lasix warns excessive diuresis may cause dehydration
Beta blockers (metoprolol, propranolol)	Less skin blood flow and sweating, low blood pressure	Propranolol: no heat wording
ACE inhibitors and ARBs (lisinopril, losartan)	Low blood pressure, less thirst; more risk with a diuretic	Zestril and Cozaar name volume depletion as a kidney risk
Lithium	Water loss, toxicity when dehydrated	”Avoid becoming overheated or dehydrated”
Antipsychotics (olanzapine, quetiapine)	Impaired sweating and temperature control	Body temperature regulation warning
SSRIs and SNRIs (sertraline, venlafaxine)	More sweating	Sweating among common side effects
Topiramate	Less sweating	Oligohidrosis and hyperthermia warning
Sedating antihistamines (diphenhydramine)	Less sweating, impaired temperature control	Benadryl: no heat wording
NSAIDs	Kidney injury with dehydration	Celebrex: monitor kidneys with dehydration
Levothyroxine	Excessive sweating	Heat intolerance as a sign of too much hormone

FAQ: medications and heat waves

What medications increase the risk of heat stroke? The CDC names diuretics, anticholinergic drugs and some psychiatric medications as the commonly prescribed ones, and its full list includes beta blockers, ACE inhibitors and ARBs, lithium, antipsychotics, SSRIs and SNRIs, tricyclic antidepressants, topiramate, sedating antihistamines, NSAIDs and stimulants. Combinations, such as an ACE inhibitor or ARB with a diuretic, add up.

Should I stop my medication during a heat wave? No, not on your own. The CDC’s guidance is that patients should avoid stopping any medicine abruptly without a plan in place; any change in dose or timing belongs to your prescriber. Ask for a hot-day plan before summer instead.

Which blood pressure medicines are risky in the heat? The CDC lists diuretics, beta blockers, calcium channel blockers, ACE inhibitors and ARBs, each for a different reason, and warns that an ACE inhibitor or ARB combined with a diuretic may significantly increase risk. Our guide to blood pressure medication covers each class.

Can antidepressants make you more sensitive to heat? They can change sweating: the CDC lists more sweating with SSRIs and SNRIs and less with tricyclic antidepressants, and the amitriptyline label names hot weather. Our guide to antidepressants answers drug by drug.

How should I store medicines in hot weather? Out of hot cars and other places that get very hot. The CDC warns that inhalers can burst, EpiPens may deliver less epinephrine, and insulin may lose effectiveness in heat.

Which medications make you more sensitive to the sun? The CDC names the antifungals flucytosine, griseofulvin and voriconazole and the antibiotics metronidazole, tetracyclines and fluoroquinolones, and recommends broad-spectrum sunscreen of SPF 30 or higher.

The bottom line on medicines and heat waves

A long list of everyday medicines raises heat risk, and the CDC’s guidance explains how: less thirst, less sweating, more fluid loss, lower blood pressure, or a drug building up when you are dehydrated. Many of them carry no heat warning on their label, so a label check is not the whole answer.

The useful step is a conversation before summer: ask your prescriber or pharmacist to go through your list, ask for a plan for hot days, keep medicines out of hot cars, and do not stop anything on your own. Our medication and heat checker shows what the labels of your own medicines say, next to the CDC’s list, and our guide to medications, saunas and cold plunges covers the sauna side.