How to recognize and treat the symptoms of mild, severe, or chronic dehydration

• Symptoms of dehydration vary depending on the severity, but can range from headaches to heatstroke.
• Causes of dehydration include exercising, being in the heat, and vomiting or diarrhea.
• To treat and prevent dehydration aim to drink between 2.5 to 3.5 liters of water a day.

Water plays a key role in nearly every system in the body from regulating temperature to cushioning joints.

Mild dehydration typically doesn't cause long-term health complications, but severe dehydration can lead to heat-related illnesses, like heat stroke, which can be fatal.

Understanding the signs and symptoms of dehydration can help you treat the condition early and reduce your risk of serious complications, like seizures and low blood pressure.

Here is what you need to know about signs of dehydration and how to properly treat it.

Signs of dehydration

How quickly dehydration symptoms develop can depend on several factors including the cause of your dehydration and your age, says Gabriel Carpio, MD, a sports medicine physician with Hoag Orthopedic Institute. Symptoms also vary based on the severity.

Mild to moderate dehydration symptoms include:

• Feeling thirsty
• Dry skin
• Headache
• Muscle cramps
• Decreased urination
• Dark or yellow urine
• Dry mouth

Severe dehydration symptoms include:

• Dizziness
• Light-headedness
• Rapid breathing
• Rapid heartbeat
• Confusion
• Fainting or unconsciousness

If you are experiencing any symptoms of severe dehydration, go to your nearest emergency room.

Dehydration symptoms often look different in children than they do in adults, Carpio says. Young children aren't always able to communicate when they're feeling thirsty, so signs of dehydration may not be apparent to parents until they are more severe.

Signs of dehydration in children include:

• Dry lips
• Decreased tear production
• Sunken eyes
• Lethargy, or a state of weariness and diminished energy
• For babies and toddlers, no wet diapers for three hours

Dehydration symptoms for those over the age of 65 are similar to symptoms seen in younger adults, Carpio says. However, older adults experience a decrease in total body fluid, meaning less of their body mass is made up of water. This makes them more susceptible to dehydration.

Note: Like kids, some elderly adults - especially those with dementia - may have trouble recognizing and communicating signs of dehydration until it becomes more severe.

Chronic dehydration

Most cases of dehydration are acute, meaning they are due to a sudden loss of fluids, like excessive sweating from exercising in the heat, Carpio says. Chronic dehydration refers to dehydration that develops over time and takes several days to treat depending on the cause.

For example, someone taking a diuretic medication that causes frequent urination may be losing more fluids daily than they are taking in, resulting in dehydration symptoms over time.

"The dehydration may take a few days or longer to fully develop or be identified depending on the consistency of fluid intake and extent of replenishment," Carpio says.

The signs of chronic dehydration are similar to the signs of acute cases, Carpio says, they just may last longer.

Dehydration causes

Not drinking enough water is one common cause of dehydration, Carpio says. Americans drink an average of 39 ounces of water a day, or about 5 cups, which is below the recommended daily fluid intake of 15.5 cups for men and 11.5 cups for women (this includes liquids from foods).

Other causes include:

• Certain illnesses, like diarrhea or vomiting that cause a loss of fluids.
• Excessive sweating. The more vigorous the exercise or the hotter and more humid the climate, the more you will sweat, which results in a loss of fluids. If you do not replenish fluids by drinking water you could become dehydrated.
• Increased urination, which may be caused by certain medications, like diuretics. Undiagnosed or uncontrolled diabetes can also lead to frequent urination.

Dehydration treatment

The treatment for any kind of dehydration, whether mild or severe, is a replenishment of fluids, says Veronica Contreras, MD, family medicine physician at AltaMed Health Services. How that's done depends on individual factors, including the severity of your dehydration and your age.

Mild dehydration can typically be treated by replacing fluids orally with small sips of water throughout the day. Sucking on ice cubes or sipping on a sports drink with electrolytes can also help replace fluids, Contreras says. In more severe cases, you may need intravenous (IV) therapy in the hospital.

For kids, oral replacement therapy (ORT), or gradually drinking water, is the preferred method for treating mild to moderate dehydration as it is less invasive and costly, says Contreras.

A 2004 review compared oral rehydration to IV therapy for children with dehydration caused by the stomach flu. It found oral rehydration was just as effective as IV treatment.

Treatment for severe dehydration in elderly adults may require IV treatment, but likely in smaller doses than for younger adults, Carpio says. Other research suggests oral replacement therapy may also be a more effective and safe treatment than IV therapy for older adults, but more research is needed.

Important: How long it may take to treat dehydration depends on many factors, Carpio says. For mild cases, you could start feeling better within minutes or hours after replacing fluids. For more severe or chronic cases, it could take several days.

Insider's takeaway

Dehydration can increase your risk for heat-related illnesses, like heat exhaustion or heat stroke, but treating dehydration early can lower your risk of complications.

Signs of mild dehydration include increased thirst, dry mouth, and dry skin. More severe symptoms of dehydration include confusion, dizziness, and loss of consciousness.

Treatment for dehydration includes replenishing lost fluids, either by increasing your fluid intake at home or receiving IV therapy in the hospital in more severe cases. You can also prevent dehydration by drinking adequate amounts of water daily.