What Arizona's Extreme Heat Actually Does to Your Medication
And what to do about it.
There's a version of summer in Arizona that most people have made peace with: stay inside during the afternoon, drink more water, don't leave anything in the car. The heat is a known quantity, and after a few years here, you develop habits around it.
What fewer people think about — and what doctors and pharmacists have been paying closer attention to — is what that same heat does to the medications sitting on the kitchen counter, or to the body that's taking them.
This isn't a minor concern. Heat interacts with medication in several distinct ways: it can physically degrade drugs before you ever take them, and it can change how your body processes and responds to drugs once you do. For older adults who take multiple medications, that interaction can amplify risks in ways that aren't always obvious.
Here's what's actually happening, and what you can do about it.
What Heat Does to the Medication Itself
Most medications you pick up from a pharmacy come with a storage instruction that gets little attention: store at room temperature, or keep between 59° and 86°F. In most of the country, for most of the year, that instruction is easy to follow without thinking about it.
In a Valley summer, it isn't.
Car interiors can reach temperatures far exceeding that range within minutes of parking in the sun. A windowsill, a bathroom cabinet near a south-facing wall, a kitchen counter near the stove — all of these can regularly exceed safe storage temperatures during the summer months. And the damage that results isn't always visible.
Heat accelerates the chemical breakdown of active drug compounds. A medication that's been stored too hot may look identical to one stored correctly — same pill, same color, same smell — but it may deliver a fraction of the intended dose. According to the FDA, expiration dates represent the last date a manufacturer guarantees a drug's full potency under proper storage conditions. Heat exposure can move that date much closer, without any indication on the packaging.
Some specific medications deserve extra attention:
Insulin should be refrigerated, and heat degrades it. If you take insulin and your blood sugar has been harder to manage than usual without an obvious explanation, storage conditions are worth examining.
Inhalers present a different kind of risk: according to the CDC, inhalers can malfunction or even burst in hot environments — including car trunks on hot days. An inhaler that's been left in a hot vehicle may not function when you need it.
EpiPens can deliver less epinephrine than intended after heat exposure, which matters enormously in an emergency situation.
Nitroglycerin and other cardiovascular medications are particularly heat-sensitive. Some formulations can begin losing potency rapidly outside of recommended temperature ranges.
For any medication, the signs of possible heat damage include tablets that are softer than usual, capsules that have stuck together, or an unusual odor. If you notice any of these, contact your pharmacist before continuing to take the medication. And be aware: the absence of visible changes doesn't confirm the medication is still effective.
What Heat Does to Your Body's Response to Medication
This is the part of the conversation that tends to surprise people, because it doesn't involve anything going wrong with the pill itself.
Heat stresses the body's ability to regulate its own temperature. To stay cool, your body increases blood flow toward the skin's surface, sweats, and pulls fluid outward. Those are normal, healthy responses — but they also change the physical environment in which your medications are working. And for a significant number of commonly prescribed drugs, that change matters.
The CDC has identified several categories of medication that can increase heat-related health risks, particularly for older adults.
Diuretics — often prescribed for blood pressure or heart conditions, and sold under names like furosemide and hydrochlorothiazide — work by increasing urination. In heat, when the body is already losing more fluid through sweat, diuretics can push dehydration further and faster than most people realize. They can also cause electrolyte imbalances and reduce the sensation of thirst, which removes one of the body's natural signals to drink more water.
Beta-blockers — atenolol, metoprolol, propranolol and similar drugs — affect the heart rate and blood pressure. They also reduce the body's ability to dilate the small blood vessels near the skin's surface, which is one of the primary ways the body dissipates heat. Taking a beta-blocker doesn't make heat dangerous by itself, but it can slow the body's cooling response at a time when that response matters.
ACE inhibitors and ARBs — lisinopril, losartan, enalapril, valsartan and related drugs — are widely prescribed for blood pressure and heart conditions. Like diuretics, they can reduce the sensation of thirst and lower blood pressure in ways that may be amplified when the body is also losing fluid to heat.
Antipsychotic medications and certain antidepressants can impair sweating — one of the body's core cooling mechanisms — and interfere with the brain's ability to regulate body temperature centrally. Someone taking these medications may not sweat normally even as their core temperature climbs.
Sleep aids, anxiety medications, and opioids — benzodiazepines, certain antihistamines like diphenhydramine, and narcotic pain medications — can cause sedation and cognitive impairment that reduces awareness of thirst and heat exposure. They can also increase fall risk, which is already higher when blood pressure is dropping in the heat.
NSAIDs — ibuprofen, naproxen, and similar over-the-counter pain relievers — can affect kidney function and increase the risk of kidney injury in people who are dehydrated.
Some antibiotics and antifungal medications can increase sensitivity to sunlight, causing sunburn-like reactions at lower levels of UV exposure than would normally produce them.
The point isn't that any of these medications is dangerous in summer — for most people, the risks are manageable with awareness and some practical adjustments. The point is that the combination of heat, dehydration, and multiple medications creates conditions where each factor can amplify the others, and where the effects can arrive gradually, without a clear trigger.
What This Looks Like in Practice
Heat-medication interactions don't usually present as a dramatic event. They're more likely to appear as a sequence of things that seem only loosely connected: feeling unusually tired, a little lightheaded when standing up, less thirsty than normal, confused in a way that seems like it might just be the heat.
Falls are a real concern. Several common medications lower blood pressure or cause dizziness; when someone stands up quickly on a hot day after not drinking enough water, the combination can cause a drop in blood pressure significant enough to result in a fall. This is not hypothetical — it's a pattern that emergency physicians see.
Dehydration can also cause the concentration of certain medications in the bloodstream to rise, because there's less fluid to dilute them. For drugs with a narrow therapeutic index — where the difference between a therapeutic dose and a toxic one is small — this matters. Lithium, used for mood disorders, is an example the CDC specifically highlights.
None of this is meant to be alarming. It's meant to make the situation concrete enough that it prompts a conversation — with your pharmacist, with your doctor, or with someone who can help you think through your specific situation.
What You Can Do
Talk to your pharmacist or doctor before summer, not after something happens. Ask specifically: given everything I'm taking, are there any medications I should be more careful about in hot weather? Are there adjustments to timing, dose, or fluid intake I should know about? This conversation is not complicated for a pharmacist to have — they have the training and the information, they just need to be asked.
Never stop taking a medication abruptly because of a concern about heat. The CDC explicitly cautions against this. If you think a medication might be interacting with heat in a way that concerns you, call your doctor's office before changing anything.
Rethink where you store your medications. The bathroom medicine cabinet is one of the worst places for medication storage year-round — humidity and temperature fluctuate significantly. A bedroom drawer, a closet shelf away from exterior walls, or any consistently cool, dry location out of direct sunlight is better. If you have medications that require refrigeration, make sure your refrigerator is maintaining appropriate temperatures, and have a plan for power outages.
Don't leave medications in your car. Not even briefly. Not even in a bag in the shade. In Arizona summers, even a short stop can expose medications to temperatures far outside their safe range.
Drink more water than you think you need. This is true for everyone in Arizona summers, but it's particularly true for people taking diuretics, ACE inhibitors, ARBs, or NSAIDs. Staying ahead of dehydration is much easier than recovering from it.
Know the warning signs of heat-related illness and heat-medication interaction: unusual dizziness or lightheadedness when standing, rapid heart rate, confusion, stopping sweating when you'd expect to be sweating, nausea, or muscle cramps. If you or someone near you experiences these, moving to a cool environment and seeking medical attention quickly matters.
Have a plan for power outages. If you take insulin or any other refrigerated medication, think through in advance what you'll do if your air conditioning or power goes out. This is an Arizona-specific consideration that's worth not leaving until it's an emergency.
A Note on the Bigger Picture
Most medication management advice is written for a generic climate. Arizona's summers are not generic. The consistent, extended, extreme heat the Valley experiences from May through September creates conditions that warrant specific attention — to storage, to hydration, to how your body is responding to drugs you may have been taking for years without any problems.
This doesn't require dramatic action. It requires the same thing most good health management requires: a periodic, honest look at your situation, and a willingness to ask a question or two before something becomes a problem.
Aster's Outreach & Social Services team can help connect you with medical resources, benefits programs, and community support. If you have concerns about managing your health through the summer — including medication-related concerns — we're a starting point, even if your need is ultimately something we refer you elsewhere for.
Resources
Aster's Outreach & Social Services team can connect you with medical resources, community programs, and benefits support. Call 480.634.1659 or reach out through our website.
Aster's Senior Centers — at Mesa Downtown and Red Mountain — offer air-conditioned gathering space, congregate meals, and community connection, Monday through Friday, 8 am to 4 pm. Call 480-964-9014 to learn more.
Your pharmacist is one of the most underused resources for medication management questions. Most pharmacies offer free consultations, and your pharmacist has access to your complete medication list and can identify interactions you might not be aware of.
The Arizona Department of Health Services (azdhs.gov) provides updated heat safety guidance each summer, including specific resources for older adults and those with chronic health conditions.
Sources: CDC, "Heat and Medications — Guidance for Clinicians," National Center for Environmental Health, last reviewed September 18, 2025 (cdc.gov/heat-health). U.S. Food and Drug Administration guidance on medication storage and expiration. American Pharmacists Association guidance on heat and medication storage, as reported by TODAY Health, July 2023.
