Dehydration happens when your body loses more fluids than it takes in. Water is essential for nearly every function in your body—from regulating temperature and keeping your joints lubricated to helping organs work properly. When you don’t have enough water in your system, your body can’t perform these basic functions as well, and that can lead to problems.
While dehydration can happen to anyone, it’s especially dangerous for babies, older adults, and people with chronic illnesses. Many people don’t even realize they’re dehydrated until they start to feel tired, dizzy, or confused. The good news is that dehydration is usually easy to treat once it’s recognized, and with a few good habits, it can often be prevented.
In this article, we’ll break down what dehydration is, what causes it, the different types, the symptoms to watch out for, how it’s diagnosed, and what treatments are available.
What Dehydration Really Means
Your body is made up of about 60% water, and every system depends on it to work properly. Dehydration occurs when you lose more fluids than you replace. This can happen slowly over time or suddenly, depending on your activity level, health status, or environment.
Mild dehydration might just make you feel thirsty or tired. But if it continues or gets worse, it can affect your blood pressure, heart rate, and organ function. In extreme cases, dehydration can be life-threatening and needs immediate medical care.
Causes and Different Types of Dehydration
There are many reasons someone might become dehydrated. One of the most common is simply not drinking enough fluids—especially during hot weather, physical activity, or illness. Your body loses water through sweat, urine, breathing, and even tears. When you don’t replace what you’ve lost, dehydration sets in.
Other causes include vomiting, diarrhea, fever, and certain medications like diuretics, which increase urination. People with diabetes may also be at risk if their blood sugar levels are high, causing frequent urination and fluid loss.
Dehydration can be broken down into a few different types:
Mild dehydration means your body is just beginning to feel the effects of fluid loss. You might feel a little thirsty or tired but otherwise okay.
Moderate dehydration occurs when fluid loss starts to affect your daily activities. You may feel dizzy, have a dry mouth, or notice darker urine.
Severe dehydration is a medical emergency. It can cause confusion, rapid heartbeat, low blood pressure, and even unconsciousness. This level of dehydration requires urgent care, often with IV fluids.
There’s also a condition called chronic dehydration, where someone is repeatedly dehydrated over time. This can be harder to spot because the symptoms may be less obvious but can still affect long-term health.
Common Symptoms to Watch For
The symptoms of dehydration vary depending on how much fluid your body has lost and how quickly. In the early stages, the signs can be subtle, but as dehydration progresses, they become more serious.
Common symptoms include:
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Dry mouth and throat
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Feeling thirsty
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Dark yellow urine or not urinating much
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Fatigue or low energy
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Dizziness or lightheadedness
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Dry or cool skin
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Headache
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Muscle cramps
In babies or young children, signs may include a dry diaper for more than three hours, crying without tears, sunken eyes or cheeks, or unusual drowsiness.
Severe dehydration can lead to rapid heartbeat, confusion, very low blood pressure, and fainting. If any of these symptoms occur, it’s important to seek medical help immediately.
How Dehydration Is Diagnosed
If your doctor suspects you’re dehydrated, they will ask about your symptoms and recent activities. They may also look at your vital signs, such as blood pressure and heart rate, which can change with fluid loss.
A physical exam may include checking your skin’s elasticity and the moisture in your mouth. Your doctor might also order blood tests to see if your electrolyte levels (such as sodium and potassium) are off. A urine test is another common way to diagnose dehydration—it can show how concentrated your urine is and how well your kidneys are working.
These tests help determine how serious the dehydration is and guide the best treatment approach.
Treatment and Recovery
The treatment for dehydration depends on how severe it is. In most cases, mild dehydration can be managed at home by drinking more fluids. Water is the best choice, but drinks with electrolytes (like oral rehydration solutions or sports drinks) can help replace lost minerals if you’ve been sweating a lot or had diarrhea.
For moderate dehydration, your doctor may recommend increasing your fluid intake and may give you an oral rehydration solution. These contain the right balance of salt and sugar to help your body absorb fluids more quickly.
Severe dehydration usually requires treatment in a hospital. You may need intravenous (IV) fluids to replace lost water and electrolytes quickly. If the dehydration is caused by an underlying illness, that condition will also need to be treated.
Preventing dehydration is often as simple as being mindful of your fluid intake. Drink plenty of water throughout the day, especially during exercise or hot weather. If you’re sick, try to take small sips of fluids regularly, even if you don’t feel thirsty. Eating water-rich foods like fruits and vegetables can also help keep you hydrated.
