WARNING: This article is meant to be a quick overview and not a detailed guide on dehydration. Professional medical care should always be sought first before attempting any of these methods.

As self-reliant people, we understand the importance of water. We store it in our homes and bug-out shelters, carry it in our vehicles, and bring it with us during every hike or workout. The problem is that even with an abundance of available water, we often neglect the water within our own bodies.

Nearly two thirds of your body weight is water, yet taking that fluid status for granted, particularly during strenuous activity, frequently leads to dehydration and death. Here we’ll discuss the factors that contribute to water loss, followed by signs and symptoms of dehydration. Lastly, we’ll discuss some strategies for fluid management.

Activity and Environment

There are several factors that contribute to fluid loss. Exercise and temperature are among the biggest causes. Clearly, the hotter the environment or the more intense and prolonged the activity, the more water we lose, especially if we naturally sweat a lot. Don’t just assume, however, that increased activity and temperature are the only things to watch out for. It’s easy to think about replacing water when it’s hot outside, but many assume replacing it during the cold, dry winter months, isn’t as critical. Dehydration can and does still occur when you’re exposed to lower temperatures.

Deconditioning also plays a part in increased fluid loss. The simple truth is that being out of shape will require you to exert more energy and sweat more than usual, which may cause some to succumb to the heat more easily. Many people don’t realize that altitude also contributes to fluid loss. The higher you go, the more you perspire and lose water through increased respiration. The water/sweat also evaporates faster at higher altitudes due to higher atmospheric pressures, especially above 5,000 feet. Being aware of the factors that contribute to water loss is important.

Obvious signs of dehydration are thirst, dark-colored urine, and fatigue, which occur in mild dehydration (less than 5-percent body fluid loss). As water loss becomes moderate (5- to 10-percent loss), we can experience worsening of the aforementioned symptoms as well as increased heart rate, weak pulse, decreased urine output, decreased sweating, and decreased levels of alertness.


When dehydration is severe (greater than 10-percent loss), the mental state can be drowsy, even obtunded, and perspiration can stop, with the skin having “goose pimples.” There’s very little urine output and the respiratory rate increases. This is a situation that requires immediate medical attention, as it puts vital organs at risk of permanent damage.

In order to estimate how much fluid to replace, there’s a simple calculation. There are more precise equations that can be found on the Internet, but here we’ll keep it simple:

1) Take your weight in pounds, and divide by 2.2 to get your weight in kilograms.

2) Since your body is essentially 60-percent water, take your weight in kilograms multiplied by 0.6 to get the liters of water contained in your body. For example, if a male is 220 pounds, then the equation is (220/2.2) x 0.6 = 60 liters of water in his body.

3) Therefore, in a case of mild dehydration (5 percent) for this 220-pound (100kg) male, who we just calculated to have 60 liters of water in his body, would result in 3L of water lost during the activity (60L x 0.05 = 3L).

So with the signs of dehydration and the simple calculations above, we’ve one way to estimate how much water is lost during activity. Another is to weigh yourself before any activity, then weigh yourself afterward to find out how much weight you lost. You can assume that the weight lost was all water weight and replenish accordingly. As a general rule, 1 liter of water is equal to about 1 kilogram of weight. So, in our example, the man who lost 3 liters of fluid would have lost 3 kilograms of weight, or approximately 6.5 pounds.

Emergency water prep filter purifier disinfectant plastic bottles 6

If you don’t have a scale and anticipate a hard workout in a hot environment, we’d recommend drinking a ½ liter of water a few hours before the event, then about 250mL of water five to 10 minutes prior to the activity. During exercise, I would recommend drinking about 250mL every 15 minutes. This latter recommendation is approximately the maximum amount of fluid an average person can absorb from the stomach in that time period.

Having a Water Survival Plan

In a survival situation, however, remember from the rules of three that you can only survive roughly three days without water. Maintaining your hydration in a survival situation is crucial. As the level of dehydration becomes more severe, fatigue can interfere with performing tasks critical to your own survival. Mental clarity diminishes rapidly but is recovered slowly. The best approach is to prevent dehydration in the first place, by drinking water while you can. Trying to drink 250mL of water every 15 minutes in a stressful bug-out scenario may be a reasonable goal, assuming your cache of water is plentiful. If you’re bugging in, you may be able to stretch that out to every one to two hours, depending on ambient temperature and activity level.

Improvised Purification

Solar water disinfection purifier filter bacteria drink bottle 6

We all know that boiling water is one way to kill harmful pathogens, but did you know that it’s also possible to reliably purify water using clear bottles and exposure to sunlight? In the following article on OFFGRIDweb, we discuss SODIS, a solar water disinfection process designed for use in developing nations: offgridweb.com/?p=8644

Oral Rehydration Salts

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Above: Oral rehydration salts often come in such small packets like this example from Chinook Medical Gear. Keep some in your medical gear stash in the event dehydration and water scarcity becomes an issue.

What about the benefit of oral rehydration salts? The World Health Organization has developed an oral rehydration salt (ORS) that consists of sodium chloride (2.6g), glucose (13.5g), potassium chloride (1.5g), and sodium citrate (2.9g). These are available through the internet; one packet is dissolved in 1 liter of water. There are other ORS out there that you can put in a bottle of water, but they can have varying amounts of these four components.

The combination of “salts” was developed from treating severe dehydration due to infectious diarrhea in developing countries, where kids and adults were losing a lot of water and potassium. The potassium replacement was important to prevent cardiac complications. The glucose was added not so much for nutrition, but to assist in getting sodium into the cells. The sodium citrate was important to neutralize the acid built up in a severely dehydrated body. Some commercial ORS may have magnesium (to help with potassium transport) and may not have the sodium citrate. The citrate would only be important in very severe cases of dehydration. In a survival situation where there’s no ORS available, you could make a solution by using 1 liter of water, 6 leveled teaspoons of sugar (25.2g), and a half teaspoon of table salt (2.9g).

Alternate Hydration Methods

What about sports drinks? While these were developed to help aid athletes to recover faster, many physicians believe that sports drinks are generally not as helpful as people believe. The benefit you may perceive is the replenishment of glucose from the activity. What’s often lacking in these sugar-heavy beverages is the balance of electrolytes to accompany the glucose. If you don’t have water, it may be a reasonable alternative to consume a sports drink; however, it’s not recommended to rely on sports drinks when water is available.

Above: Do not rely solely on sports drinks in a dehydration situation if you have access to clean water.

Should you avoid caffeine? Contrary to popular belief, research shows that caffeine usually doesn’t act as a diuretic. A diuretic is a substance that makes you urinate more than the fluid consumed and is commonly used for those people with heart failure. Multiple factors can sway the argument toward caffeine being a mild diuretic. Are you dehydrated while drinking caffeine? Are you used to drinking caffeine? How much caffeine is being consumed at a time? If the answer to those questions is yes, yes, and more than 360 mg of caffeine, then you may notice a small diuretic effect. If you’re foraging for food in a survival situation, keep in mind that plants such as dandelion, onion, garlic, grapes, watermelon, and asparagus can have a diuretic effect.

You may have heard that zinc can be helpful in preventing dehydration since it has been studied in Africa during infectious diarrhea outbreaks (e.g. cholera). Zinc boosts the immune system and aids in intestinal transport of glucose and sodium. Studies have suggested that in cases of severe infectious diarrhea, patients who were given zinc had a significant decrease in severity and duration of diarrhea. They were also less likely to have recurrence of symptoms for months afterward.

Zinc supplements are often used to boost water retention and absorption.

Zinc supplements are often used to boost water retention and absorption.

The amount of zinc used in these studies was up to 20g a day for those over 6 months old, and 10g a day for those under 6 months old. Keep in mind that these were impoverished countries where zinc ingestion through foods was poor. In our western culture, we certainly get our fair share of zinc in our foods. In a survival situation, we have foods like garlic, raspberries, pumpkin seeds, cashews, almonds, and asparagus that all contain good amounts of zinc. It’s not known whether consuming zinc in a milder form of dehydration is beneficial.

Health Considerations

There are a few physiological items to discuss regarding dehydration as well. First, your gastrointestinal system always seems to be the first organ sacrificed when blood volume is low (e.g. dehydration). When you’re low on fluid, your body makes sure that your heart, brain, and lungs have all the fluid they need to keep you alive. If you eat while you’re dehydrated, your body doesn’t do a great job digesting the food, because the stomach was shut down to shift blood (fluid) to other more important organs. This is one of the reasons that you don’t feel hungry when you’re dehydrated.

Another factor in nutrition and fluid loss during a long-term survival scenario is a protein in our body called albumin. Although albumin has several important roles in the body, for our purposes here, its job is to keep fluid inside the blood vessels. If we re-visit the rules of three, we know we can survive about three weeks without food. Although we have albumin stored in our body, these levels can be depleted over a few weeks, especially if food is scarce. When albumin levels are low, water leaks out of the blood vessels and into the places where the tissues cannot use the water (this is called “third spacing”). This process decreases blood volume, decreases blood pressure, and creates an environment that leads to organ failure and death.

Optimal fluid management during activities or during survival situations is essential to maintain peak performance. By recognizing the signs and symptoms of dehydration, we might prevent a progression of dehydration that affects our performance. By managing our fluid intake to meet the demands of activity and the losses of fluid, we can prepare to perform at peak levels.

About the Author

David Miller, DO, FACOI, is an internist in private practice. Diagnosed with Type 1 diabetes in 1990, he has a unique perspective on patient care and disease management. Experiences away from the office include being a fight doctor for regional MMA bouts and a team physician for a Division I university in west central Illinois. Dr. Miller is an instructor for the Civilian Crisis Response Team (medical section) based out of Indianapolis.

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