Note From Your Clinician

Dehydration During Hot Weather: What You Need to Know

What Is Dehydration?
Dehydration happens when your body loses more fluid than it takes in. During hot weather, your body sweats more to cool itself down. If you don't drink enough fluids to replace what you lose through sweat, you can become dehydrated. Dehydration can range from mild to severe and, if untreated, can lead to serious health problems including kidney injury, heat exhaustion, and heat stroke.

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Who Is Most at Risk?
- Infants and young children — they lose fluids quickly and may not be able to tell you they are thirsty
- Older adults — the sense of thirst decreases with age, and some medical conditions or medications increase risk
- People with chronic conditions — especially heart disease, kidney disease, diabetes, or obesity
- People taking certain medications — including diuretics ("water pills"), blood pressure medications, antihistamines, and
   some psychiatric medications. Ask your doctor if any of your medications increase your risk
- Outdoor workers and athletes — heavy physical activity in the heat causes rapid fluid loss
- People without access to air conditioning

Warning Signs of Dehydration
Mild to Moderate Dehydration:
- Increased thirst
- Dry mouth, lips, or tongue
- Dark yellow urine or urinating less than usual
- Headache
- Dizziness or lightheadedness
- Tiredness or weakness
- Muscle cramps
Severe Dehydration — Seek Medical Attention Immediately:
- Very dark urine or no urine output
- Rapid heartbeat or rapid breathing
- Confusion, irritability, or drowsiness
- Fainting
- Sunken eyes
- Skin that stays "tented" when pinched (does not bounce back quickly)
- In infants: no tears when crying, sunken soft spot on the head, no wet diapers for 3 or more hours
 

How to Prevent Dehydration in Hot Weather
Drink plenty of fluids:
- Don't wait until you are thirsty to drink — by the time you feel thirsty, you may already be mildly dehydrated
- Water is the best choice for most activities lasting less than 1 hour
- For physical activity lasting 1 hour or more, use a sports drink that contains electrolytes (sodium and potassium) to replace
   what is lost in sweat
- Avoid alcohol, caffeine, and sugary drinks, which can worsen dehydration
Stay cool:
- Stay indoors in air-conditioned spaces during the hottest parts of the day (typically 10 a.m. to 4 p.m.)
- If you don't have air conditioning, visit a cooling center, library, or shopping mall
- Use fans, but be aware that fans alone may not be enough when temperatures exceed 99°F (37°C)
- Take cool showers or baths
- Wear lightweight, light-colored, loose-fitting clothing
- Use a wide-brimmed hat and sunscreen outdoors
Adjust your activity:
- Limit strenuous exercise or outdoor work during peak heat
- Take frequent breaks in the shade or a cool area
- If you must work or exercise outdoors, gradually increase your time in the heat over 7 to 14 days to allow your body to adjust
  (this is called "acclimatization")
Watch out for others:
- Check on elderly neighbors, relatives, and friends regularly during heat waves
- Never leave children or pets in a parked car — temperatures inside a car can rise dangerously within minutes
- Monitor children closely for signs of dehydration during outdoor play
 

What to Do If You or Someone Else Becomes Dehydrated
For mild to moderate dehydration:
- Move to a cool, shaded area immediately
- Sip water or an oral rehydration solution (such as Pedialyte for children)
- A simple homemade rehydration drink: add ¼ to ½ teaspoon of table salt to 1 liter (about 34 ounces) of water. You can add a
   few teaspoons of sugar or lemon juice for taste
- Rest and avoid further physical activity
- Remove excess clothing
Call 911 or go to the emergency room if:
- The person is confused, not making sense, or loses consciousness
- The person cannot keep fluids down due to vomiting
- Symptoms do not improve within 30 minutes of resting and drinking fluids
- The person has a very high body temperature (above 103°F / 39.4°C)
- The person stops sweating despite being in the heat
- The person has a seizure

A Note About Medications
Some common medications can increase your risk of dehydration or heat-related illness. These include:
- Diuretics (water pills)
- Beta-blockers and other blood pressure medications
- Antihistamines (allergy medications)
- Some psychiatric medications (antipsychotics, antidepressants)
- Stimulants
Do not stop taking any prescribed medication without talking to your doctor. Instead, ask your doctor whether you need to take extra precautions during hot weather.
 

Key Takeaway
Dehydration during hot weather is preventable. Drink fluids regularly, stay cool, limit outdoor activity during peak heat, and watch for warning signs — especially in children, older adults, and those with chronic health conditions. When in doubt, seek medical attention promptly.

The above covers the causes, warning signs, prevention, and management of dehydration during hot weather, based on current evidence from the American Academy of Family Physicians, the CDC, and NEJM reviews on heat-related illness.