Dehydration: Questions and Answers

If you don't take in enough fluids to meet your body's needs, or if you lose too much water through sweat and other bodily fluids, you could become dehydrated.

Anyone can become dehydrated—but it's especially dangerous for young children, older adults and pregnant women. Learn about what causes dehydration, the symptoms of dehydration and how to tell if you're drinking enough water.

What is dehydration?

Dehydration occurs when your body loses more fluids than you take in. If your body doesn't have enough water, it cannot function well. Water helps your body in many different ways. For instance, your body uses water to digest foods, absorb nutrients, control body temperature and get rid of waste.

What causes dehydration?

Dehydration can happen for several reasons. Causes of dehydration include:

• Heavy sweating. When you sweat during exercise or in hot weather, you lose fluids. Hot, humid conditions and vigorous, prolonged exercise can cause heavy sweating. If you don't take in enough liquids to replace lost fluids, you could become dehydrated.
• Vomiting or diarrhea. Sudden, severe diarrhea causes you to lose a significant amount of water and minerals in a short amount of time. If there is vomiting in addition to diarrhea, the fluid loss is even greater.
• Fever. Having a fever causes fluid loss, and the higher the fever is, the more fluids you lose. You're more at risk for dehydration if you have a fever in addition to diarrhea and vomiting.
• Increased urination. Taking some medications, such as diuretics (water pills) and certain blood pressure medicines, or having undiagnosed or uncontrolled diabetes can cause you to urinate more than usual. This can cause dehydration.

What are the effects of dehydration?

Dehydration can lead to dangerous complications, such as:

• Heat illnesses. If you're sweating heavily from exercise or by simply being outdoors in the heat, and you don't drink enough water, you can develop mild cramps from dehydration. More severe cases of dehydration can lead to heat exhaustion or even heat stroke, which is a life-threatening emergency.
• Seizures. When the body loses fluids, it loses more than just water: Essential electrolytes, including potassium and sodium, are also lost through sweat and bodily fluids. When electrolytes aren't balanced, electrical signals in the body can malfunction. This can cause involuntary muscle contractions and even loss of consciousness.
• Kidney issues. Repeated or chronic dehydration causes urinary tract infections (UTIs), kidney stones, and possibly, kidney failure.
• Hypovolemic shock (low blood volume shock). One of the most serious complications of dehydration, hypovolemic shock, happens when low blood volume decreases blood pressure and the amount of oxygen in your body. This condition is life-threatening.

What are the symptoms of dehydration?

• Increased thirst and dry mouth
• Urinating less than normal or having dark-colored urine
• Tiredness
• Dry skin
• Dizziness
• Confusion
• Decreased skin turgor (skin elasticity)

Can dehydration cause headaches?

Yes. Headaches from dehydration are fairly common. Certain types of headaches, including migraines, may be triggered by dehydration.

Can dehydration cause a fever?

Yes. A fever is known to cause dehydration, and dehydration may contribute to fevers in young infants. Fever can also occur in adults who are dangerously dehydrated because water is needed to control body temperature. This is a medical emergency.

Can dehydration cause nausea?

Yes. Nausea and vomiting can lead to dehydration. However, nausea from dehydration is not a common symptom.

Can dehydration cause dizziness?

Yes. Dehydration can cause dizziness and even fainting.

What's the link between dehydration and blood pressure?

In some cases, dehydration can lower blood pressure levels.

What are the signs of dehydration in children?

Symptoms of mild dehydration in young children and babies include:

• A slightly dry mouth
• Increased thirst

If your child has signs of mild dehydration, they likely do not need immediate medical care. Instead, treat the condition at home by giving them fluids to drink. Watch for signs of worsening dehydration, including:

• Decreased urination (not going to the bathroom or having a wet diaper for 6 hours or more)
• Crying without tears
• Dry mouth and tongue
• Being unusually sleepy or drowsy
• Sunken eyes or cheeks
• High fever

If your child has symptoms of moderate to severe dehydration, get them medical help right away.

Dehydration in pregnancy

Dehydration can increase your risk for pregnancy-related complications such as neural tube defects, low amniotic fluid levels and preterm labor. Aim to drink 8-12 cups of water each day during pregnancy to prevent dehydration, and avoid activities that can cause overheating, such as spending an extended amount of time outside on hot, humid days.

Dehydration in the elderly

Older adults have an increased risk of dehydration for several reasons: As we age, our body's fluid reserves decrease and our sense of thirst may also not be as strong as it once was. Taking certain medicines and having illnesses, such as diabetes, can also contribute to fluid loss. In addition, if you have mobility challenges, it can be difficult to get water for yourself as often as you need to.

How can I tell if I'm drinking enough water?

To learn if you're well hydrated, check the color of your urine. If it's pale yellow or clear, you're likely taking in enough fluids. If it's dark-colored, you probably need to take in more water. You can also try the dehydration skin test. This test checks your skin turgor. Decreased skin turgor is a symptom of dehydration. To perform this test, grasp the skin between two of your fingers or on your lower arm, back of your hand or abdomen. If your skin has normal turgor, it should snap back into its regular position quickly. If it has poor turgor, it will likely take some time to return to its normal position.

How can I prevent dehydration?

Thirst isn't always a reliable indicator for water needs. In fact, some people, especially older adults, don't feel thirsty until they're already dehydrated. If you have symptoms of early dehydration, such as heavy sweating and increased thirst, drink small amounts of water. Taking in too much water can overload your stomach and cause vomiting, which can worsen dehydration.

Make sure you're drinking plenty of fluids and eating foods that contain water, such as fruits and vegetables, throughout the day so you stay well-hydrated. If you wonder if caffeine-containing beverages, such as coffee and tea, dehydrate you, know that drinks that contain caffeine count toward your daily fluid needs. These beverages may cause you to urinate slightly more than normal, but they don't seem to increase the chance of dehydration.

Drink extra water when you're in hot weather and when you are sick. Also, be mindful to drink plenty of water before, during and after being physically active. When you exercise for an extended amount of time or in hot conditions, consider drinking a sports beverage to replace lost electrolytes.

If you or your loved one is unable to keep fluids down, has diarrhea for more than 24 hours, has bloody or black stool or is disoriented and much less active than normal, call your health care provider. Getting prompt treatment for dehydration can help reduce the risk of complications.

Published on April 29, 2019

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