Hydration: What to Know for Hot Weather

Know the signs and risks of dehydration and keep the fluids flowing to avoid overheating this summer or whenever temperatures rise.

Dehydration, which occurs when you lose more fluid than you take in, can lead to everything from minor cramps and heat exhaustion to seizures and potentially life-threatening heatstroke or shock. Photo: Rido / Shutterstock

This article originally appeared in the Tufts Health & Nutrition Letter, published each month by the Friedman School of Nutrition Science and Policy. Find out how to get expert guidance on healthy cooking, eating, and living.

It’s hot out! High temperatures increase the risk of dehydration. Fluids are critical to optimal body function. They help regulate body temperature, control blood pressure, deliver nutrients and oxygen to cells, and aid proper functioning of the gastrointestinal system. When fluid levels drop, a wide variety of systems in the body are affected. Knowing the signs and symptoms of dehydration—and how to avoid them—can get us safely through the heat of summer.

Dehydration Defined

Dehydration occurs when you lose more fluid than you take in. It can lead to everything from minor cramps and heat exhaustion to seizures and potentially life-threatening heatstroke or shock.

Thirst is one way the body alerts us of low fluid levels. “Drink to satisfy your thirst,” says Klemens Meyer, MD, a nephrologist and director of Dialysis Services at Tufts Medical Center. Other symptoms are fairly general and include dry lips, mouth, or tongue; headache, dizziness, or lightheadedness; fatigue or lethargy; lack of focus; muscle weakness or muscle cramps; and rapid breathing. Urine color is a possible indicator of hydration in children and young adults, but not necessarily in older adults. When hydrated, urine is light and straw-like in color. Very dark colored urine is a sign of dehydration. “If your urine is dark, drink water to make it lighter, but not so much that it looks like water,” says Meyer.

Dehydration Risks

We normally lose fluid in sweat, urine, and our breath. Other causes of fluid loss include diarrhea and vomiting. Illness and certain medications (including laxatives, oral medications for type 2 diabetes, and diuretics) can increase risk for dehydration. Athletes who sweat a lot for a significant period of time require increased fluid intake.

“Although thirst is a good indicator to drink water to prevent dehydration in most people,” Meyer says, “the very young and the very old may be the exception.” Infants and young children, who don’t have a lot of body mass, are sensitive to even small amounts of fluid loss, and they don’t have the ability to clearly express their thirst. The body’s fluid volume decreases with age, and so can the ability to sense thirst, so older adults are at higher risk of becoming dehydrated. On top of that, studies show adults ages 60 and older consume about two fewer cups of fluid a day than younger individuals.

How to Hydrate

Fluid needs depend on many factors, including body size, age, activity level, climate, and diet. Because needs are so individual, there are no recommended intake levels that apply to everyone. Instead, the U.S. National Academies of Sciences Institute of Medicine has set an “Adequate Intake” level. In addition to the fluids we get from foods (especially fruits and vegetables), men should, on average, consume at least 12 cups of fluid a day from water and other beverages. Women should have a minimum of nine cups. Consider putting that much water in a container at the start of the day and trying to get through it by day’s end.

Water is a great choice, but other unsweetened beverages, such as low-fat or fat-free milk and fortified soy beverage, can support fluid intake while helping us reach our dietary intake recommendations for different food groups and nutrients. While electrolyte drinks are advertised to help keep you hydrated, studies have shown electrolyte loss through typical physical activity is generally small, so these (often sweet) beverages are unnecessary for most situations.

Spruce up water with a splash of fruit juice or slices of fresh or frozen fruits and/or fresh herbs. Try a sparkling or mineral water for a change (just be sure there are no added sugars). Unsweetened coffee and tea are good options as well and can be served over ice. Almost all fruits and vegetables have high water contents, so include plenty of water-rich seasonal or frozen fruits and vegetables, like watermelon, strawberries, cucumbers, celery, and tomatoes in your dietary intake.

Take the heat off this summer by ensuring you consume refreshing fluids and water-rich produce, and be on the lookout for signs of dehydration.

Important Notice: This article was also published at https://now.tufts.edu by their News Staff where all credits are due.


The watching, interacting, and participation of any kind with anything on this page does not constitute or initiate a doctor-patient relationship with Dr. Farrah™. None of the statements here have been evaluated by the Food and Drug Administration (FDA). The products of Dr. Farrah™ are not intended to diagnose, treat, cure, or prevent any disease. The information being provided should only be considered for education and entertainment purposes only. If you feel that anything you see or hear may be of value to you on this page or on any other medium of any kind associated with, showing, or quoting anything relating to Dr. Farrah™ in any way at any time, you are encouraged to and agree to consult with a licensed healthcare professional in your area to discuss it. If you feel that you’re having a healthcare emergency, seek medical attention immediately. The views expressed here are simply either the views and opinions of Dr. Farrah™ or others appearing and are protected under the first amendment.

Dr. Farrah™ is a highly experienced Licensed Medical Doctor certified in evidence-based clinical nutrition, not some enthusiast, formulator, or medium promoting the wild and unrestrained use of nutrition products for health issues without clinical experience and scientific evidence of therapeutic benefit. Dr. Farrah™ has personally and keenly studied everything she recommends, and more importantly, she’s closely observed the reactions and results in a clinical setting countless times over the course of her career involving the treatment of over 150,000 patients.

Dr. Farrah™ promotes evidence-based natural approaches to health, which means integrating her individual scientific and clinical expertise with the best available external clinical evidence from systematic research. By individual clinical expertise, I refer to the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice.

Dr. Farrah™ does not make any representation or warranties with respect to the accuracy, applicability, fitness, or completeness of any multimedia content provided. Dr. Farrah™ does not warrant the performance, effectiveness, or applicability of any sites listed, linked, or referenced to, in, or by any multimedia content.

To be clear, the multimedia content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any website, video, image, or media of any kind. Dr. Farrah™ hereby disclaims any and all liability to any party for any direct, indirect, implied, punitive, special, incidental, or other consequential damages arising directly or indirectly from any use of the content, which is provided as is, and without warranties.