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Is My Horse Dehydrated? 10 Clear Signs of Equine Dehydration

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When my granddaughter and I approached her horse, which typically reacts joyfully, stood still in his paddock, we knew something was amiss. My first thought was, could he be dehydrated?

Horses suffering from an extreme lack of water and minerals are dehydrated. Signs of dehydration include lethargy, red mucous membranes, skin tenting, loss of appetite, excessive sweating or no sweating, high heart rate, dark urine, dizziness, and fever.

Equine dehydration is a dangerous condition and requires attention immediately. Some signs of equine dehydration are subtle, but others are easily recognizable.

Picture of horses in a pasture

Horses dehydrate when they lose too much fluid.

Horses dehydrate when they lose more fluid than they take in, resulting in not having enough water and other fluids for their body to function correctly. If the deficit isn’t replaced, the horse becomes dehydrated.

Dehydration in animals is not much different than it is in humans. However, it is especially dangerous for horses. The most common cause of dehydration in horses is caused by overexertion in high temperatures.

Horses are very efficient in dissipating heat through sweat and respiration, which is excellent for cooling their bodies; however, both reduce the volume of water and electrolytes their organs need.

Racehorses can lose as much as 5% of their body weight during a one-mile race. The amount of fluid and electrolyte loss is influenced by temperature, humidity, and the length of the race.

The risk of dehydration caused by extreme fluid loss is why trainers emphasize proper hydration both before and after a horse runs in a race.

Horses also become dehydrated from bouts of severe diarrhea, fever, lack of access to clean water, medications, and hot climates. Most cases of mild dehydration can be reversed by giving the animal water and some electrolytes.

picture of a vet checking a horse for signs of dehydration,

Signs of dehydration in horses.

Horses display various signs of dehydration. If you think your horse is dehydrated, move him to a shaded spot, rinse him, and allow him to drink, then contact the veterinarian.

Here are some common signs of equine dehydration:

Red mucous membranes

If a horse is healthy and well-hydrated, the color of its gums should be pink. Deviations could be caused by dehydration but also could result from blood loss, anemia, or infection. Pale mucous membranes are a typical sign of dehydration in horses.

Looking at a horse’s mucous membranes is useful for quickly evaluating a horse’s health. These tissues line body cavities, such as the gums, and inside the nostrils. These membranes secrete mucus to keep them moist and protected and are supplied with blood.

One easy way to check your horse’s gum is to perform a capillary refill time test. Push on your horse’s gums and release the pressure; the membranes should “pink up” within one to two seconds.

If it takes two more than two seconds for the pressure point to return to its pink state, your horse shows signs of dehydration. Also, note the amount of saliva on his gums. A dry mouth is another indication a horse isn’t adequately hydrated.

The first color indicator of dehydration in a horse’s gums is the reddening of the tissue where it meets the teeth and a paling of the rest of the gums above. If dehydration advances, the mucous membranes continue paling and eventually turn bluish, then purplish.

These colors will correspond with longer delays in the capillary refill time. Sometimes a horse’s gums will turn a deep red. When hydration falls to these levels in animals, septic or endotoxin shock occurs.


Lethargy in horses can be a sign of dehydration but also an early symptom of equine diseases. Swamp Fever, Potomac Horse Fever, and many other disorders’ early symptoms are lethargy and diarrhea.

If your horse appears quieter than usual following strenuous exercise, it’s likely displaying early signs of dehydration. Take preventive action immediately and offer your horse water and electrolytes. It’s easier to prevent dehydration at this stage than fight it in advanced settings.

If the disease is left untreated, it can lead to shock, permanent lameness, and even death. Early diagnosis and quick treatment increase the likelihood of recovery significantly.

We all have owned a lazy horse, but typically horses are lively and alert animals if you notice a sudden change in your horse’s demeanor, it is likely caused by an underlying physical condition.

Signs of a sluggish horse include hanging lip, lowered head, not eating, and standing in the corner of a stall or paddock without showing interest in anything around it.

Skin tenting

A quick method used by horsemen to check their horses’ hydration is a “skin tent” test. Normal skin tissue has a high percentage of water and is very elastic.

When a horse is dehydrated, its skin tissues are “sticky,” move slowly, and are less likely to spring back to their normal state after pinching. To perform the “skin tent” test, squeeze a horse’s skin at its shoulder, pull it upwards into a tent-like shape, and then release it.

Normal horse skin should flatten out within one second after you let it go. If the skin takes longer to return to normal, this is indicative of dehydration; horse skin that takes longer than four seconds is severely dehydrated and needs immediate attention.

This standard tent test isn’t an accurate measurement of hydration but only another tool to quickly assess a horse. It’s most reliable when used by owners who are familiar with their horse’s skin reaction to the test in a normal state.

Sweating/Not sweating.

Horses lose a lot of fluid during exercise; if the fluid isn’t replaced, the animal will become dehydrated. Sweat is a response to heat. When skin temperature rises, the blood vessels dilate, and blood flow increases.

Hot, humid environments and strenuous workouts increase the amount of sweat and loss of fluids. It’s critical for competitive horses that are working for extended periods to maintain correct hydration for the proper functioning of organs, such as the heart, muscles, brain, and kidneys.

The sweat glands increase the secretion of moisture to the skin surface. The adrenal glands assist the process during activity. The process, of course, is more technical, but this is a general outline.

During periods when a horse’s body is strained, extensive amounts of fluids are released as sweat to regulate their body temperature. Excessive sweating can lead to severe dehydration.

Chronic dehydration can cause anhidrosis in horses. Anhidrosis is the inability to sweat, both in humans and horses. Typically the condition develops over time and can be caused by various factors, including genetics, diet, climate, and chronic dehydration.

In a horse suffering from anhidrosis, something caused the sweat glands to stop working. The condition is challenging to reverse and is often permanent. Preventing the disease from occurring could be as easy as keeping your horse hydrated.

picture of a horses eyes that may be be showing the early signs it dehydrated,

Dull, dry eyes

A horse’s eye surface is an indicator of an animal’s general level of hydration. A dehydrated horse may have dull, dry-looking eyes. The conjunctival sac of a horse’s eye is a mucous membrane.

Under normal conditions, it secretes viscous mucus that keeps the eyes moist and protected. When horses are dehydrated, their eyes become dull-looking and dry. A dehydrated horse’s eyes may look as though they are sunken into its skull.

Loss of appetite

Horses love feeding time, so if you notice your horse disinterested in his feed, it likely has an underlying physical issue. One condition that causes a horse to stop eating is dehydration.

The reason a horse loses its appetite when dehydrated could be related to its general feeling of sickness. However, the animal could also suffer from colic or intestinal pain created by the lack of proper bodily fluids and electrolytes.

High heart rate

When horses become dehydrated and lack necessary electrolytes, they often display a rapid heart rate. Typical horses in decent shape have a resting heart rate between 36-42 beats per minute.

Horse owners should have a general idea of their horse’s standard resting heart rate because there is a wide variance in acceptable equine heart rates. What is normal for one horse can be extreme for another.

Resting heart rates over 60 could be a sign of dehydration. Endurance racehorses that become dehydrated in a race often exhibit incredibly high heart rates.

A high heart rate is an early sign of fluid depletion and can easily be reversed with water and electrolytes’ introduction.


Fever is most commonly associated with an infection; however, it’s also a sign of dehydration. When a horse can’t control its body because it lacks adequate fluid, it may display fever-like symptoms.

Horses’ average body temperature varies between 98 to 101 degrees. But their temperature does fluctuate throughout the day. In warmer climates, a horse’s temperature is typically higher in the afternoon than in the mornings.

Fever can be a symptom of dehydration or a cause. Horses having an infection sweat excessively, and if they don’t replace the lost fluids, they will dehydrate.

You can check your horse’s temperature with a rectal thermometer, and it’s recommended that you do it at least once a month to have a baseline body temperature on all your horse.

Dark urine

A healthy horse’s urine is yellow or straw-colored and might be cloudy, foamy, and a little darker or lighter yellow. If it turns brown, something is amiss, and dehydration is the most likely culprit.

Urine color is one of the best signals of a horse’s hydration level – clear urine indicates a well-hydrated animal and darker urine means it’s dehydrated.

When a horse is dehydrated, the volume of water in its body is drastically decreased, and its kidneys start retaining water. Therefore, less water is released in their urine, leading to it being more concentrated and darker.

You can also look at the moisture content in a horse’s feces as an indication of hydration. Animal feces should have some water content. Step on your horse’s feces and see if water comes out.

Disoriented or dizziness

Appropriate body fluid content is one of the keys to maintaining proper blood flow. When a horse is severely dehydrated, blood volume and blood pressure decrease and sufficient levels of oxygen aren’t delivered to the horse’s brain, leading to dizziness and disorientation.

How to tell if a horse is dehydrated

A complete blood chemistry analysis is the most accurate method to determine if your horse is dehydrated. You may expect a thirsty horse would be an unmistakable signal that your animal is dehydrated, but you would be wrong.

Sometimes dehydrated animals will avoid drinking. That is why it’s essential to take preventative steps and increase water intake before exercise and during hot weather.

Picture of my horse grazing.

Treatments for dehydration

Treatment when riding

If you suscept your horse is overheating while riding a long distance, it’s best to dismount, give your horse water, and take a break. If possible, unsaddle the horse remove all tack, and bathe it with cold water.

It’s also a good idea to scrap excessive water from your animal and repeat running water over its entire body; repeat this process. Water left on the horse becomes warm and will insulate the heat.

Once you’ve finished washing, put the horse in a well-shaded area and, if possible, use a fan to help cool the animal. Of course, offer your horse fresh, clean water during the cool-down period.

IV treatment

Horses that experience excessive fluid loss due to dehydration are in a dangerous state of low blood volume. Veterinarians use saline solutions and other fluids to restore blood volume.

Typical intravenous solutions include normal saline with added potassium and possibly calcium. Sometimes a veterinarian may use hypertonic saline solutions along with plasma or blood to restore fluid volume. 

Hypertonic solutions are used to replace the water/salt balance in the animal’s bloodstream. Some severely dehydrated horses may require up to 80 liters of fluid over 12 hour period to rehydrate

How long does it take for horses to get dehydrated?

Horses drink approximately a gallon of water per 100 pounds of body weight, or about 10 gallons a day for a normal-sized animal. The amount of water intake does vary based on its climate, fitness level, and the amount it is worked.

The length of time it takes a horse to become dehydrated for a lack of available water depends on the same factors, fitness, climate, and exertion. But typically, a horse starts showing signs of dehydration within two days of being deprived of water.

Horses deprived of water for three to four days can develop severe physical problems, organs will begin to shut down, and irreversible damage to tissues is likely,

two.year .old

Preventing dehydration

When horses sweat, they lose minerals such as chloride, sodium, and potassium, all necessary for proper bodily function. These electrolytes need replenishing, and in many cases, horses don’t get enough to replace their losses in hay or feed, so electrolyte supplements are required.

To ensure horses drink enough water, provide daily salt supplementation. Salt increases the animal’s desire to drink; without salt in their system, horses lose the desire to drink.

Here are some more things you can do to ensure your horse stays hydrated:

  • Provide access to fresh, clean water, use a horse trough in a pasture, and large buckets for stalls.
  • Access to a salt block, or give a daily salt supplement of 1 tablespoon per 500 pounds of body weight.
  • After your horse sweats excessively, provide an electrolyte supplement. Choose a good electrolyte supplement; an optimal one should have at least 12 grams of chloride, about 6 grams of sodium, and 4 grams of potassium.
  • Provide shade for horses to escape the sun; if you keep your horse in a stall, make sure it has adequate ventilation.
  • We feed crimped oats soaked in water to horses needing extra hydration. We also add our supplements during this feeding.

Following these easy steps should keep dehydration at bay.

Recommended electrolyte supplement:

Picture of horses in a pond.

The Final Word on Equine Dehydration

Extreme dehydration can lead to severe physical consequences and even death. A horse may need intravenous fluids and other treatments to prevent organ damage.

When you see signs of dehydration in your horse, get it cool, and provide plenty of fluids right away. If you intend to work your horse, make sure it is well hydrated before you begin and allow your horse to drink throughout the day.

Dehydration can lead to colic, laminitis, multi-organ failure, and even death.

Below is a helpful YouTube video that explains how to check your horse for dehydration.

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