How much water should I drink for heat exhaustion? A guide to proper rehydration

October 30, 2025 •

5 min read

According to the CDC, drinking one cup (8 oz) of water every 15–20 minutes is recommended when working in the heat. But what about when it's too late and you're experiencing heat exhaustion? Knowing how much water should I drink for heat exhaustion and the appropriate steps is crucial for a safe and speedy recovery.

Quick Summary

Learn the specific fluid intake recommendations for treating heat exhaustion, including how much and how often to drink. Discover when to use water versus an electrolyte-rich drink and what crucial steps to take for a swift recovery from heat-related illness.

Key Points

Initial Intake: Drink 2-3 cups of cool water or a sports drink immediately upon recognizing heat exhaustion symptoms.
Follow-up Hydration: Continue drinking 1 cup of fluid every 15-20 minutes for the next 1-2 hours until symptoms improve.
Electrolytes Matter: For heavy or prolonged sweating, use a sports drink or an Oral Rehydration Solution (ORS) to replenish lost salts and minerals.
Monitor Progress: Track your hydration status by checking your urine color; it should be pale yellow or clear.
Cool the Body: Alongside fluid intake, move to a cool place and apply cold, wet cloths to the skin to lower body temperature.
Seek Medical Help: Call emergency services immediately if symptoms worsen, don't improve within an hour, or if signs of heat stroke appear.

What is Heat Exhaustion?

Heat exhaustion is a heat-related illness that occurs when the body overheats due to prolonged exposure to high temperatures and dehydration. It is the body's warning sign that it can no longer regulate its temperature effectively through sweating alone. This condition can progress to the more severe and life-threatening heat stroke if not treated promptly. Symptoms include heavy sweating, weakness, dizziness, headache, nausea, and a rapid pulse. The primary problem in heat exhaustion is the loss of water and salt through excessive sweating, which must be replenished.

Immediate Steps to Treat Heat Exhaustion

If you or someone else is showing signs of heat exhaustion, immediate action is necessary to prevent the condition from worsening. The first and most critical step is to move to a cooler environment. This can be an air-conditioned building, a shady spot, or a cool room. Here is a step-by-step guide:

Move to a cool place: Find a shady spot or go inside to an air-conditioned room as quickly as possible.
Lie down and elevate legs: Resting on your back with your legs raised higher than your heart level helps improve blood circulation.
Loosen clothing: Remove any tight or unnecessary clothing to help your body cool down.
Apply cooling measures: Use cool, wet cloths or take a cool shower or bath. Applying damp towels to the neck, armpits, and groin is also effective.
Begin fluid intake: Start drinking cool fluids slowly. This is where knowing the right amount and type is vital.

How Much Water to Drink for Heat Exhaustion

For an adult or teen recovering from heat exhaustion, the initial goal is to quickly replace lost fluids. Recommendations suggest drinking 2 to 3 cups (16 to 24 ounces) of cool liquid right away. After the initial intake, it's important to continue rehydrating at a controlled pace. The recommended follow-up is to drink approximately 1 cup (8 ounces) every 15 to 20 minutes for the next one to two hours. Sipping fluids slowly rather than guzzling large amounts is recommended to prevent stomach upset.

Water vs. Electrolytes: What to Drink

Plain, cool water is often sufficient for mild heat exhaustion, especially if the person is eating regular meals that replace lost salt. However, if the person has been sweating heavily for a prolonged period (several hours), an electrolyte-rich sports drink can be more effective for replacing the sodium and potassium lost through sweat. Oral Rehydration Solutions (ORS) are specifically formulated with an optimal balance of electrolytes and glucose to maximize fluid absorption, making them a very effective option for moderate dehydration.

What to Avoid

When rehydrating, it's just as important to know what drinks to avoid as it is to know what to consume. Caffeinated and alcoholic beverages should be avoided, as they can act as diuretics and contribute to further dehydration. Highly sugary drinks like soda or fruit juice are also not ideal because their sugar concentration can draw fluid into the intestines and potentially worsen diarrhea or delay fluid absorption.

Comparison of Rehydration Fluids

To help decide on the best fluid for different situations, here is a comparison of options:


Feature	Plain Water	Sports Drinks	Oral Rehydration Solutions (ORS)
Best For	Mild dehydration and general hydration.	Replenishing fluids and electrolytes during or after prolonged, heavy sweating.	Moderate dehydration from heat exhaustion or illness (diarrhea/vomiting).
Electrolytes	None added.	Formulated with electrolytes like sodium and potassium.	Specifically balanced for optimal fluid and electrolyte absorption.
Sugar Content	None.	Contains sugar for energy and to aid water absorption.	Low sugar content, balanced with electrolytes.
Availability	Widely available.	Readily available at most stores.	Available in pharmacies, some grocery stores, or online; some can be homemade.
Consideration	Does not replace electrolytes lost during heavy sweating.	Excess calories may be a concern for some.	The most effective option for restoring balance during moderate dehydration.

How to Prevent Heat Exhaustion

Prevention is always the best strategy when it comes to heat-related illnesses. Here are some key tips to stay hydrated and avoid heat exhaustion:

Drink regularly throughout the day, even if you don't feel thirsty. Thirst is often a sign that dehydration has already begun.
Monitor your urine color. Pale yellow or clear urine is a good indicator of adequate hydration. Dark yellow or amber-colored urine suggests dehydration.
Dress appropriately by wearing light-colored, loose-fitting, and breathable clothing.
Avoid the hottest times of the day, which are typically between 11 a.m. and 4 p.m..
Replenish electrolytes if you are sweating heavily for an extended period, such as during strenuous exercise.
Avoid dehydrating beverages like alcohol and caffeine, especially when in a hot environment.

When to Seek Medical Attention

While many cases of heat exhaustion can be managed at home, it is crucial to seek prompt medical attention if symptoms are severe, worsen, or do not improve within an hour of treatment. Immediate medical help (calling emergency services) is required if the person shows any signs of heat stroke, which is a life-threatening emergency. Signs of heat stroke include a high body temperature (above 104°F/40°C), hot and dry or damp skin, rapid and strong pulse, confusion, slurred speech, or loss of consciousness. If in doubt, it is always safer to err on the side of caution and seek professional medical help.

Conclusion

Understanding how much water should I drink for heat exhaustion is essential for prompt and effective recovery. For an adult, this involves drinking 2-3 cups of cool fluid immediately, followed by 1 cup every 15-20 minutes for a couple of hours. While water is a good start, electrolyte-rich sports drinks or Oral Rehydration Solutions are recommended for moderate dehydration or after prolonged heavy sweating. By combining correct fluid intake with cooling measures and avoiding harmful beverages, you can safely reverse heat exhaustion and prevent it from escalating to a more dangerous heat stroke. For further guidance on treatment and prevention, consult reliable sources like the Mayo Clinic, the Red Cross, or the CDC.

Resources

Frequently Asked Questions

Heat exhaustion results from excessive fluid and salt loss due to high temperatures and leads to heavy sweating, dizziness, and nausea. Heat stroke is more severe, with a body temperature over 104°F, hot/dry skin, and a change in mental state like confusion or slurred speech, and requires immediate medical attention.

For an adult, you should drink 2-3 cups of cool fluids immediately after moving to a cool place. After that, continue to sip 1 cup every 15-20 minutes for about an hour or two.

For mild heat exhaustion, water is often sufficient. However, if you have been sweating heavily for a prolonged period, sports drinks or oral rehydration solutions are better because they replenish the electrolytes (salts) lost through sweat, which water does not.

If nausea or vomiting prevents drinking, you can try sipping slowly and frequently. If you cannot keep fluids down, it is important to seek medical attention, as you may require intravenous (IV) fluids.

You should avoid alcoholic and caffeinated beverages, as they can cause further dehydration. Also, steer clear of very sugary drinks, which can upset your stomach and hinder proper fluid absorption.

A simple way to check your hydration status is by observing your urine color. Pale yellow or clear urine is a good sign of adequate hydration, while dark yellow indicates you need to drink more fluids.

Yes, a simple homemade ORS can be made by mixing half a teaspoon of salt and six teaspoons of sugar in one liter (about 4 cups) of clean drinking water. However, pre-packaged ORS from a pharmacy ensures the correct balance and is often recommended.

With proper rest and rehydration, most people feel better within an hour. However, it's wise to take it easy for at least 24 hours afterward and avoid strenuous activity in the heat, as your body is more sensitive to high temperatures during recovery.