What Is the Number One Drink for Dehydration? An Expert Analysis

October 10, 2025 •

4 min read

According to a study published in the American Journal of Clinical Nutrition, some beverages can actually be more effective for long-term hydration than plain water, depending on their composition. This raises a critical question: what is the number one drink for dehydration, and how does that answer change based on the underlying cause?

Quick Summary

This article explores the most effective drinks for rehydration, analyzing their components, from electrolytes and carbs to proteins. Compare options like ORS, milk, and sports drinks to choose the ideal fluid for recovery after illness, exercise, or everyday needs.

Key Points

Oral Rehydration Solution (ORS) is #1 for severe dehydration: Endorsed by the WHO, ORS is the most effective medical-grade drink for correcting dehydration caused by illness due to its precise electrolyte-glucose balance.
Milk offers superior fluid retention: Studies show that milk is more hydrating than water over longer periods due to its natural electrolytes, proteins, and carbohydrates, making it an excellent post-exercise recovery drink.
Plain water is best for everyday hydration: For general needs and mild dehydration, calorie-free plain water is sufficient and the most recommended option.
Sports drinks are for intense exercise only: High-sugar sports drinks are useful for endurance athletes to replenish carbs and electrolytes during prolonged, intense activity but are not ideal for general or illness-induced dehydration.
Electrolytes are crucial for proper rehydration: Minerals like sodium and potassium, lost through sweating or illness, are vital for maintaining fluid balance and are necessary for effective rehydration.
Coconut water is a natural electrolyte source: High in potassium but lower in sodium, coconut water is a natural, lower-sugar option for rehydration.

Understanding the Science of Rehydration

Rehydration is more complex than simply replenishing lost water. When the body loses fluids, it also loses essential electrolytes, such as sodium and potassium. These minerals are vital for regulating fluid balance, nerve function, and muscle contractions. The effectiveness of a rehydration drink depends on its ability to replenish both water and electrolytes efficiently.

Why Plain Water May Not Always Be Enough

For mild, everyday thirst, plain water is the best and simplest choice. However, during intense periods of fluid loss, such as from severe sweating, vomiting, or diarrhea, water alone can actually dilute the remaining electrolytes in the body. A key study from St. Andrews University developed a 'Beverage Hydration Index' (BHI) to compare how different drinks are retained in the body over time. This research found that certain beverages, such as Oral Rehydration Solution (ORS) and milk, led to better fluid retention than plain water.

Top Contenders for Dehydration

Oral Rehydration Solution (ORS)

For correcting moderate to severe dehydration, especially from illness, Oral Rehydration Solution is the undisputed champion. Endorsed by the World Health Organization (WHO) and UNICEF, ORS contains a precise, medically-formulated blend of salts and glucose designed for maximum absorption via the sodium-glucose cotransport mechanism in the intestines. It is particularly effective for those with diarrhea or vomiting. While commercially prepared packets are recommended, especially for children, homemade versions can also provide a starting point.

Milk

Surprisingly, milk consistently ranks as one of the most hydrating beverages in studies, often outperforming sports drinks and water in terms of fluid retention. The reason lies in its combination of natural electrolytes, proteins, and carbohydrates. The proteins and fats in milk slow down gastric emptying, allowing for a more gradual and sustained hydration. Post-workout, chocolate milk is also effective for replenishing muscle glycogen stores.

Coconut Water

A popular natural option, coconut water is rich in potassium, a crucial electrolyte often lost during sweating. It's a lower-sugar, calorie-friendly alternative to many sports drinks. However, it is naturally low in sodium, so for rehydration after heavy sweating where significant sodium is lost, it may need to be paired with a salty snack.

Sports Drinks

For athletes engaging in intense, prolonged exercise (over 60-90 minutes), sports drinks provide a rapid source of carbohydrates for energy and electrolytes like sodium to replace what is lost in sweat. However, their high sugar content makes them an inefficient and calorie-heavy choice for general rehydration needs or for dehydration caused by illness. Low-sugar versions are available, but ORS is still superior for medical rehydration.

A Comparison of Rehydration Drinks


Feature	Oral Rehydration Solution (ORS)	Milk (Skim/Low-Fat)	Sports Drinks	Plain Water
Best For	Medical-grade rehydration from illness, heatstroke, or severe fluid loss.	Post-exercise recovery and sustained hydration.	Intense, prolonged exercise (over 60-90 mins).	General, everyday hydration and mild dehydration.
Electrolyte Content	High sodium, potassium, and chloride in a scientifically balanced ratio.	Natural source of sodium, potassium, calcium, and protein.	Varies, generally lower sodium than ORS and higher sugar.	Contains very few electrolytes unless enhanced.
Sugar Content	Low and controlled, specifically formulated for optimal absorption.	Contains natural lactose (milk sugar) and carbs for energy replenishment.	Typically high in added sugars, designed for rapid energy.	Zero calories and no sugar.
Fluid Retention	High BHI, very effective for retaining fluid.	High BHI due to carbs, proteins, and electrolytes.	Moderate; less effective for fluid retention than ORS or milk.	Moderate, but can dilute electrolytes during heavy fluid loss.

Choosing the Right Drink for Your Situation

For Everyday Hydration: The simplest and most effective choice is plain water. Most people can stay adequately hydrated by drinking when thirsty. Flavor infused water with lemon, lime, or cucumber if desired.
For Intense Exercise: If you are a serious athlete or have been exercising intensely for over an hour, a sports drink can provide quick carbohydrates and replenish electrolytes lost through sweat. For general workout rehydration, milk is a potent alternative.
For Illness (Vomiting/Diarrhea): Oral Rehydration Solution (ORS) is the number one medical choice for correcting dehydration caused by illness. It is available as a powder to mix with water and is better than high-sugar sports drinks, which can sometimes worsen diarrhea.
For Kids and Elderly: It's important not to give only plain water to infants or young children with dehydration from illness, as it can worsen electrolyte imbalance. Oral rehydration solution is the recommended option. For elderly individuals, a low-sugar electrolyte drink or natural sources like milk or broth can be beneficial.
To Make a Homemade Solution: A basic electrolyte drink can be made with coconut water, a pinch of salt, and a squeeze of lime juice. The balance, however, will not be as precise as a medical-grade ORS.

Conclusion: Context is King

Ultimately, there is no single "number one" drink for dehydration that fits all situations. While plain water is the ideal choice for everyday, general hydration, the optimal solution for correcting moderate to severe dehydration is a medically formulated Oral Rehydration Solution (ORS). For sustained hydration and post-exercise recovery, milk offers a superior fluid retention profile due to its unique blend of electrolytes, carbs, and proteins. Understanding the cause of your fluid loss—whether it's illness, exercise, or simple thirst—is the key to choosing the most effective rehydration drink.

For more in-depth information on ORS, consult the guidelines published by the World Health Organization (WHO).

Frequently Asked Questions

No. While sports drinks contain electrolytes, their high sugar content is formulated for athletic performance, not for medical rehydration from illness. The high sugar can sometimes worsen diarrhea. ORS has a scientifically-balanced, lower-sugar formula designed for optimal absorption during illness.

According to a study on the 'Beverage Hydration Index', milk was found to be more hydrating than plain water over a four-hour period. Its combination of protein, carbohydrates, and natural electrolytes allows for more sustained fluid retention in the body.

If you are experiencing heavy fluid loss from intense exercise, prolonged heat exposure, vomiting, or diarrhea, you are likely losing significant electrolytes. For these situations, a drink with added electrolytes, like ORS or milk, is more effective than plain water for rapid recovery.

The fastest way to rehydrate, particularly from severe fluid loss, is to consume an Oral Rehydration Solution (ORS). Its specific glucose-to-sodium ratio facilitates rapid absorption of both fluid and electrolytes by the intestines.

Homemade versions using ingredients like water, salt, and juice can provide some electrolyte replenishment. However, it is difficult to achieve the precise balance of a medical-grade ORS. For severe dehydration, especially in children or the elderly, commercially prepared ORS is safer and more effective.

For children with dehydration from illness, Oral Rehydration Solution is the recommended choice. Giving only plain water is not advised as it can worsen electrolyte imbalances. For everyday hydration, water is sufficient.

Yes, coconut water is a good natural source of potassium and can be a healthy option for general hydration. However, it is lower in sodium than medical ORS, so it's less ideal for situations involving significant sodium loss from sweat or illness.