How Does Dehydration Affect the Body?

Kenneth Knowles, MD
Medically reviewed by Kenneth Knowles, MDMarch 10th, 2020
How Does Dehydration Affect the Body

As you bask in the glory of summer, it’s crucial that you keep yourself hydrated. With heat waves reaching record-breaking heights throughout the country, medical experts are stressing the hidden dangers of dehydration and its effects on both the mind and body, now more than ever. In fact, new studies have shown that dehydration can critically impair a person’s cognitive performance in as little as two hours—affecting the ability to focus, perform executive functions, and control motor coordination. To better understand dehydration and the impact it has on the body, let’s explore the causes and symptoms, and review preventative measures that you can take to beat the summer heat.

What is Dehydration?

In technical terms, dehydration is the result of excessive body water loss. This typically occurs when an individual loses more than two percent of their bodily fluids. While the body naturally loses fluid throughout the day—via perspiration, bowel movements, urination, and various other day-to-day happenings—if it is not replenished, dehydration can quickly set in. This ailment can restrict, and can even prohibit, the body’s ability to carry out its necessary functions, potentially leading to serious health issues.


Dehydration can occur for a number of reasons, and most people will experience its milder symptoms at some point in their lives: extreme thirst, headaches, fatigue, and dizziness. Some popular causes of dehydration include:

  • Excessive sweating – Sweat is the body’s natural cooling mechanism, releasing fluids to maintain body temperature. Prolonged exposure to heat and vigorous exercise increase the amount you sweat, thus increasing the amount of fluid you lose.
  • Certain medications – Diuretics, antihistamines, blood pressure medications, and antipsychotics can increase the risk of dehydration, as they encourage frequent urination.
  • Vomiting or diarrhea – This is the most common cause for dehydration, causing a tremendous loss of water and electrolytes in a short amount of time.

Risk Factors

Dehydration can affect anyone, but there are certain demographics that are at greater risk. Young children, the physically disabled, and the elderly, for example, often rely on caretakers to provide water. Therefore, in some cases, their need for hydration may go unnoticed for a longer period of time than it would for an able-bodied adult or older child who can recognize their thirst and act on it. Others at greater risk for dehydration include:

  • People with chronic illnesses – If you have diabetes, chronic kidney disease (CKD), Alzheimer’s, or other pre-existing health condition, you are at a higher risk of dehydration.
  • Athletes – Whether you are a professional athlete or just someone who enjoys exercising outside, it’s vital that you stay hydrated. In warm, humid months, this becomes even more important, as exercising in this weather can increase your body temperature and the need for more fluids.

How Does Dehydration Affect the Body & Mind?

You’ve heard it before, and you’ll hear it again: About 60 percent of the human body is made of water—making hydration essential for regulating bodily functions. Water is used to perform a multitude of specialized operations for the body: protecting organs, flushing out waste and toxins, and carrying nutrients and oxygen to the cells. Thus, limiting the amount of water your body has access to can critically affect its ability to perform these functions, reducing your internal sodium and electrolyte levels, and causing physical and cognitive impairments. This can lead to difficulty performing tasks that require attention, motor coordination, and executive function—grammatical reasoning, mental math, decision making etc. This is why it’s vital that you monitor your daily fluid intake and watch for symptoms relating to dehydration.


What Are the Symptoms of Dehydration?

Most mild cases of dehydration are characterized by thirst; however, this isn’t always a reliable indicator. In fact, most people don’t feel thirsty until they are already dehydrated. Spooky, right? That’s why it’s imperative that you increase your water intake throughout the day, even more so when you’re ill or spending time outside on a sweltering summer’s day. That being said, most signs and symptoms of dehydration can vary greatly depending on a person’s age, health, and body.

Infants & Toddlers

Dehydration in small children and infants can be difficult to recognize, as they aren’t always able to effectively communicate their discomfort. Signs of dehydration in children often include, but are not limited to:

  • Sunken eyes and cheeks
  • Dry mouth and tongue
  • No wet diapers for three or more hours
  • Irritability


To determine whether you are experiencing dehydration as an adult, look for the following symptoms:

  • Extreme thirst
  • Dark-colored urine
  • Dizziness
  • Fatigue
  • Headaches
  • Confusion
  • Less frequent urination
  • Nausea

When to Seek Medical Treatment

While most occurrences of dehydration can be reversed by simply increasing fluid intake, severe cases of dehydration may require immediate medical attention. To pinpoint the degree of dehydration, your doctor may order a blood test and urinalysis. Nevertheless, the only truly effective way to treat dehydration is to replace lost fluids and electrolytes. Emergency rooms (ERs) often deliver this intravenously (through the vein) for maximum body absorption and speedy recovery.

Serious Complications

If not addressed, serious cases of dehydration can severely complicate the body’s and mind’s ability to perform. In some cases, this can lead to hallucinations and organ shutdown. Other complications caused by untreated dehydration can include:

  • Urinary and kidney problems
  • Seizures, or involuntary muscle contractions
  • Loss of consciousness
  • Heat injury, mild heat cramps, heat exhaustion, and heatstroke
  • Hypovolemic shock, or low blood volume shock caused by a drop in blood pressure and oxygen

Tips for Preventing Dehydration This Summer

The best way to treat dehydration is to stay hydrated. This doesn’t mean you need to chug a gallon of water every hour. Medical experts advise you to drink about two liters, or half a gallon, of filtered water every day. This is a general guideline, and depending on your circumstances, you may require more or less water. Here are some other tips to help you stay hydrated this summer:

  • Hydrate before, during, and after exercising.
  • Monitor your hydration based on your level of thirst and the color of your urine; darker urine could indicate dehydration.
  • Always carry a reusable water bottle and take frequent sips from it throughout the day.
  • Eat a well-balanced diet of grains, greens, protein, fruits, and veggies.

DispatchHealth: The Mobile Medical Experts

Man in bed receiving care

If you believe that you or a loved one is experiencing critical dehydration symptoms, and are in need of on-demand medical attention, turn to the health experts at DispatchHealth. We take our mobile medical service to your home, or place of need. Our medical team consists of either a physician assistant or nurse practitioner, along with a DispatchHealth medical technician (DHMT) and an on-call physician. Our team will arrive with medical kits that contain nearly all of the tools and tests found in traditional emergency room (ER) facilities—including blood tests, urinalysis, urine cultures, and IVs. Specializing in providing convenient and affordable treatment to those with complicated, non-life-threatening health issues, physical disabilities, or mental health issues, we ensure that everyone has access to high-quality and convenient healthcare.

Stay hydrated!

Contact DispatchHealth via phone, mobile app, or online to schedule an in-home medical evaluation. We’ll arrive at your home within a few hours.

If you are experiencing a life-threatening emergency, please call 911 or go to the nearest emergency department.


DispatchHealth relies only on authoritative sources, including medical associations, research institutions, and peer-reviewed medical studies.

Sources referenced in this article:

The DispatchHealth blog provides tips, tricks and advice for improving lives through convenient, comfortable healthcare.

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