Heat Exposure Risk Assessment Tool
Your Heat Risk Assessment
When the temperature rises, most people think about drinking more water, staying in the shade, and wearing light clothes. But for people taking diuretics or anticholinergics, heat isn’t just uncomfortable-it can be life-threatening. These medications, commonly prescribed for high blood pressure, heart failure, overactive bladder, and depression, interfere with your body’s ability to cool itself. And many people don’t even realize it.
How Diuretics Put You at Risk in the Heat
Diuretics, often called water pills, help your body get rid of extra fluid. That’s great for lowering blood pressure or reducing swelling in the legs. But when it’s hot, that same mechanism becomes dangerous. Medications like furosemide (Lasix), hydrochlorothiazide (Microzide), and chlorthalidone (Hygroton) make you pee more. That means you lose water and electrolytes-especially sodium and potassium-faster than your body can replace them.During heat exposure, your body naturally sweats to cool down. Sweating uses up even more fluid. If you’re on a diuretic, you’re already starting from a deficit. Research shows that people taking loop diuretics have a 37% higher chance of being hospitalized for heat-related illness during summer months-even when temperatures are only in the low 80s (26-28°C). That’s not a heatwave. That’s a typical July day in many parts of the U.S. and Europe.
Low potassium from diuretics can also cause muscle cramps, irregular heartbeat, and dizziness. In extreme heat, those symptoms can quickly turn into heat exhaustion or worse. A 2022 study at Massachusetts General Hospital found that nearly half of heart failure patients on diuretics needed their doses temporarily lowered during a major heatwave. Not because they wanted to, but because their bodies couldn’t handle the stress.
Why Anticholinergics Block Your Body’s Cooling System
While diuretics make you lose fluid, anticholinergics stop you from sweating at all. That’s the problem. Sweating is your body’s main way of cooling down. If that’s turned off, your core temperature can rise dangerously fast-even if you’re sitting still in the shade.Common anticholinergics include oxybutynin (Ditropan) for overactive bladder, tolterodine (Detrol), and older antidepressants like amitriptyline (Elavil). These drugs block acetylcholine, a chemical that tells your sweat glands to activate. Studies show that medications with a high anticholinergic burden score (ACB = 3) can reduce sweating by 30-50%. That’s not a small effect. It’s like turning off your air conditioner while the sun beats down.
And here’s the scary part: many people don’t feel the danger coming. Anticholinergics can cause confusion, memory problems, and drowsiness. So if you’re starting to feel dizzy or nauseous from heat, you might not realize it-or you might forget to tell someone. That’s why heat-related deaths in older adults often go unnoticed until it’s too late. During the 2021 Pacific Northwest heat dome, 63% of those who died from heat had taken either a diuretic or an anticholinergic.
What You Should Do Right Now
If you take either of these medications, here’s what matters most:- Don’t stop taking your meds. Never skip or cut your dose without talking to your doctor. Stopping your diuretic or anticholinergic suddenly can cause dangerous rebounds-higher blood pressure, fluid buildup, or worsening bladder symptoms.
- Drink water regularly. Don’t wait until you’re thirsty. Sip water all day, even if you’re not active. If you’re on a fluid restriction for heart failure, ask your doctor if it’s safe to loosen it during hot weather. Many patients need to drink more in summer, not less.
- Wear the right clothes. Light-colored, loose, breathable fabrics help. Avoid dark colors and tight synthetics. They trap heat and make sweating less effective.
- Use sunscreen. Many anticholinergics make your skin more sensitive to the sun. You can burn faster and get rashes more easily.
- Know the warning signs. Headache, dizziness, nausea, muscle cramps, fast heartbeat, confusion, or dry skin with no sweat are red flags. If you have them, get to a cool place immediately. Call 999 if symptoms don’t improve in 15 minutes.
Ask Your Doctor These Questions
Don’t wait for a heatwave to think about this. Talk to your doctor now:- Is my medication known to increase heat risk? What’s its anticholinergic burden score?
- Should I adjust my dose during hot weather? Is there a safer alternative?
- Do I need to check my electrolytes more often in summer?
- Can you help me create a heat safety plan-like who to call if I feel unwell?
Some clinics now use digital tools to flag patients on high-risk medications during heat alerts. If yours doesn’t, ask if they can add you to a phone check-in list during extreme weather. A simple daily call from a neighbor or family member can save your life.
The Bigger Picture: Climate Change Is Making This Worse
The UK has seen a 47% increase in days over 90°F since 1970. Heatwaves are longer, hotter, and more frequent. By 2050, parts of southern England could see over 30 days above 30°C each year. That’s not just inconvenient. For people on diuretics or anticholinergics, it’s a growing public health crisis.Right now, most heat safety advice is generic: “Stay cool. Drink water.” But that’s not enough for people on these meds. We need better systems-doctors who ask about medications during heat alerts, pharmacies that flag high-risk prescriptions, and community programs that check on vulnerable people.
Until then, the responsibility falls on you and your care team. Know your meds. Know your risks. Know your plan.
When to Seek Emergency Help
Heat illness can turn deadly in under an hour. If you or someone you care for is on one of these medications and shows any of these signs, call 999 immediately:- Body temperature above 39°C (102.2°F)
- No sweating despite being hot
- Confusion, slurred speech, or loss of consciousness
- Seizures
- Weak or rapid pulse
Don’t wait to see if it gets better. Heat stroke kills. And if you’re on a diuretic or anticholinergic, your body doesn’t have the normal defenses.
Can I still go outside if I take diuretics or anticholinergics?
Yes-but you need to be extra careful. Avoid being outside during the hottest part of the day (11am-3pm). If you must go out, wear a hat, use sunscreen, carry water, and stay in the shade. Check in with someone before and after. Never push through dizziness or nausea.
Do all anticholinergics stop sweating the same way?
No. Medications are ranked by anticholinergic burden (ACB). Drugs with ACB = 3-like oxybutynin, amitriptyline, and some bladder meds-have the strongest effect. Others, like loratadine (Claritin) or diphenhydramine (Benadryl), have lower scores (ACB = 1 or 2) and pose much less risk. Ask your pharmacist to check your meds.
Should I avoid caffeine and alcohol if I’m on these meds?
Yes. Both caffeine and alcohol act as mild diuretics and can make dehydration worse. They also interfere with your body’s ability to regulate temperature. Stick to water, diluted fruit juice, or electrolyte drinks approved by your doctor.
Is there a safer alternative to my current medication?
Possibly. For overactive bladder, mirabegron (Betmiga) works differently and doesn’t block sweating. For depression, newer SSRIs like sertraline have much lower anticholinergic effects than older tricyclics. But switching meds isn’t simple-it depends on your condition, other drugs you take, and your overall health. Talk to your doctor before making any changes.
What should I do if I live alone and have no one to check on me?
Register with your local council’s welfare check program. Many UK areas offer free check-ins for vulnerable residents during heat alerts. You can also use a smartwatch with fall detection and temperature monitoring, or set daily phone alarms to remind yourself to drink water and cool down. Don’t assume you’ll feel it in time. Heat illness sneaks up.
