What is dehydration?

Dehydration is when you don’t have enough water in your body. The human body normally contains a lot of water. In fact, 50% to 60% of your body weight comes from water. It helps keep your body healthy and working well. Mild dehydration can cause problems with blood pressure, heart rate, and body temperature. Severe dehydration can also cause weakness or confusion. In extreme cases, it can lead to brain damage and even death.

Everyone loses body water daily through sweat, tears, breathing, urine, and stool. This water is replaced by drinking fluids and eating foods that contain water. Dehydration can have many causes. You may have lost water from diarrhea or vomiting. Or you may be sweating from exercise or hot weather. Loss of water often leads to an imbalance of electrolytes in the body. Electrolytes are minerals and salts that the body needs to function. They include sodium, potassium, magnesium, and calcium.

What causes dehydration?

Dehydration can be caused by:

• Sweating from hot weather, exercise, sauna use

• Diarrhea

• Vomiting

• Fever

• Some medicines that cause extra urination, such as diuretics (water-pills)

• Some diseases that cause you to urinate more, such as poorly controlled diabetes

Who is at risk for dehydration? 

You are more at risk if you:

• Have diarrhea

• Have vomiting

• Are in hot weather

• Are sweating a lot from exercise

• Are an older adult age 60 or older

• Have certain diseases or illnesses

What are the symptoms of dehydration?

Symptoms can occur a bit differently in each person. They can include:

• Thirst

• Tiredness

• Dizziness

• Lightheadedness

• Muscle cramps

• Dry mouth

• Less urine

• Urine that’s dark yellow or even light brown in color

• Headache

• Dry skin or tongue

• Fainting

• Confusion

• Fast heart rate and breathing

The symptoms of dehydration can look like other health conditions. See your healthcare provider for a diagnosis.

How is dehydration diagnosed?

Your healthcare provider will ask about your symptoms and health history. The provider may also ask about recent illness or activity. You will also have a physical exam. Your blood pressure, temperature, and heart rate will be checked. You may have blood or urine tests.

How is dehydration treated?

Treatment will depend on your symptoms, your age, and your general health. It will also depend on how severe the condition is. You also may be treated for diarrhea, vomiting, or a high fever if illness caused your dehydration.

For moderate to severe dehydration, you may need IV (intravenous) fluids. Severe dehydration is a medical emergency. It needs to be treated right away with IV fluids in a hospital.

For mild dehydration, you can drink fluids. You may need to restore not just water, but also electrolytes, such as sodium and potassium. Sports drinks can replace water and electrolytes. You can also drink water, fruit juices, tea, and soda.

Don't have drinks with caffeine. These include some energy drinks, teas, sodas, and coffee drinks. Don’t drink alcohol. Caffeine and alcohol may cause your body to lose more water.

Talk with your healthcare providers about the risks, benefits, and possible side effects of all treatments.

What are possible complications of dehydration? 

Severe dehydration that is not treated can cause kidney damage, brain damage, and death.

What can I do to prevent dehydration?

Advice varies. On average, an adult should drink about 2 to 3 quarts of fluid per day. Drinking 12 8-ounce glasses of fluid every day would help reach this goal. Drink more if you are in hot weather or exercising. Drinks may include:

• Water

• Fruit juices

• Sports drinks. Be careful of the sugar in these drinks, especially if you have diabetes.

• Other drinks that have electrolytes

• Soda with no caffeine

• Tea with no caffeine

• Coffee with no caffeine

If you have been diagnosed with a kidney or heart disease, ask your healthcare provider how much and what types of fluids you should drink to prevent dehydration. When you have kidney or heart disease, fluid can build up in the body. This can be dangerous to your health.

When should I call my healthcare provider?

Call the healthcare provider if you have:

• Diarrhea more than 5 times a day

• Continued vomiting

• Small amount of blood (red or black color) or mucus in diarrhea

• Small amount of blood in vomit

• Belly pain

• Swollen belly

• Fever of 100.4°F (38°C) or higher, or as directed by your healthcare provider

Key points about dehydration

• Dehydration is when you don’t have enough water in your body.

• Symptoms can include thirst, dry mouth, and less urine.

• Mild dehydration can cause problems with blood pressure, heart rate, and body temperature.

• Severe dehydration can also cause weakness or confusion. In extreme cases, it can lead to kidney damage, brain damage and even death.

• For mild dehydration, you can drink fluids (but not alcohol or caffeine). These include sports drinks, water, fruit juices, and noncaffeinated tea and soda.

• For moderate to severe dehydration, you may need IV (intravenous) fluids. Severe dehydration is a medical emergency. It needs to be treated right away with IV fluids in a hospital.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.