Dehydration in Horses

Published Jan. 5, 2023
Horses drinking

In This Article


What is Dehydration in Horses?

Dehydration can occur to any horse of any age, in any location. Athletes, horses with conditions such as anhidrosis, and horses living through significant weather changes in the summer or winter may be more likely to experience dehydration. It is important to keep a close eye on your horse’s water intake, exercise level, and learn to monitor for signs of dehydration or discomfort, as these can be signs of an underlying issue.

Symptoms of Dehydration in Horses

Knowing what to look for when it comes to dehydration is fairly simple. Signs you might notice if your horse is dehydrated include:

  • Fatigue or less energy than usual

  • Decreased appetite

  • Dry skin

  • Colic

Causes of Dehydration in Horses

Dehydration is common in hot or humid regions, during very cold times of the year, especiallywhen a horse may be less willing to drink water, or if they cannot find it available. Athletes, such as racehorses, can easily become dehydrated when they exercise hard and sweat excessively.

An overly stressed horse may pace constantly and sweat, and not have interest in drinking–becoming dehydrated. Extended periods of travel on the horse trailer may lead your horse to have a decreased appetite and thirst. Other causes include “tying up” or exertional rhabdomyolysis, diarrhea and colitis, and other underlying medical conditions.

How Veterinarians Diagnose Dehydration in Horses

To determine the extent to which your horse may be dehydrated, your veterinarian will perform a thorough physical examination and check the following:

  • Skin tent test: This test can also be performed at home. If you’re concerned your horse seems drier to the touch or is acting lethargic, you can grab a small piece of skin on the neck or shoulder and create a tent. The skin should be fairly elastic and should return to its normal position in a second or two. A delayed reaction, or if the skin stays tented, is an indication of dehydration.

  • Check gum color, consistency, and capillary refill time (CRT): This is another quick check or rough estimation that can give you important information at home. To check a CRT, you or your veterinarian will gently pull up the horse’s lip and check the gum color; normal should be a light pink. Gently push on the gum and then remove your finger. That spot will be white and should return to normal color in less than 2 seconds typically. This will also allow you to see your horse’s gum hydration. The gums should be moist, and not tacky, if your horse is adequately hydrated. You may get false estimates if your horse has just had a sip of water or if the gums have been pulled up repeatedly in a short period of time.

  • Heart rate may also be elevated (normal heart rate for a horse is 20-40 beats per minute), which you can note during a basic physical exam performed at home, especially if you keep a stethoscope in your first aid kit.

To evaluate an exact measurement of your horse’s dehydration, your veterinarian will pull a blood sample and run a packed cell volume (PCV) test.

Your veterinarian may also run other bloodwork to check for electrolyte imbalances. Calcium, potassium, or other additives can be administered in IV fluids.

Treatment of Dehydration in Horses

Depending on the severity of your horse’s dehydration and other clinical signs, your horse may need treatment ranging from some electrolytes added into their food and water at home, to intravenous (IV) fluids and intense monitoring and treatment at a veterinary hospital.

If your horse is mildly dehydrated at home, your veterinarian may administer water and electrolytes via nasogastric (NG) tube. They will pass a tube through your horse’s nose, down the esophagus, into the stomach. This is a typical part of a colic examination, so it will be performed if your horse is showing colicky signs (down/rolling, decreased appetite, pawing, lethargy, etc.) to check for reflux or excessive gas in the stomach.

Your veterinarian may also recommend a few liters of IV fluids. They can run this on site or may recommend a trip to the local veterinary clinic so your horse can have further diagnostics performed and IV fluids administered over a longer period of time. If your horse has an underlying disease or colic causing dehydration, they may require anti-inflammatories, antibiotics, muscle relaxers, or other medications.

Recovery and Management of Dehydration in Horses

With appropriate management for the primary cause of dehydration, most horses recover uneventfully from these events. Your horse may need to be rested for several days to a week before resuming any sort of physical activity, depending on the severity. Potential secondary conditions that might occur with dehydration include:

  • Colic: if your horse is systemically dehydrated, the intestines and food material in the gastrointestinal (GI) tract will also be dehydrated, and impactions are much more likely

  • Kidney damage

  • Exercise intolerance

  • Weakness

To prevent dehydration in horses, there are several practices you can implement at home. Having the knowledge of what to look for, and your horse’s particular habits, can help you prepare especially in times of stress, exercise, or significant weather changes.

  • Electrolytes are a huge help in promoting water intake in horses. Administering paste electrolytes before travel or a stressful event can encourage your horse to stay hydrated. Daily powder electrolytes is a great supplement worth discussing with your veterinarian, particularly in the warmer months. This can also be implemented in the late fall/early winter as it starts to get colder, as horses often drink less during this transition. They don’t believe they’re thirsty, and often start to feel frisky in the cold, so can get dehydrated much faster.

  • In the cold, ensuring water is easily accessible is a crucial part of winter horse care. Water tank heaters/deicers will keep the water from freezing. Bucket warmers or adding warm water a few times a day in a warm and cozy location will also help your horse drink an adequate amount of water.

  • If your horse is a chronic non-sweater and has anhidrosis, a daily dark beer may be recommended during the warmer months to promote appropriate sweating.

Dehydration in Horses FAQs

How do you know when your horse is dehydrated?

If your horse is dehydrated, you may notice signs such as decreased energy or appetite, dry skin, or uncomfortable signs of colic.

How long does it take for a horse to rehydrate?

Depending on how dehydrated your horse is, this process can take an hour or two, all the way up to a day or two. If your horse is very sick and dehydrated, your veterinarian will likely keep your horse on IV fluids overnight or for a few days to first correct dehydration, then maintain it while other underlying issues are addressed—your horse may not be able to regulate hydration on their own or not be willing to drink.

How do you rehydrate a sick horse?

Depending on the cause and severity of the dehydration, this abnormality can be corrected by administration of electrolytes and oral fluids, or IV fluids.

What happens if a horse doesn’t drink enough water?

If your horse does not consume enough water, they can become dehydrated, colic, or may weaken their immune system and become more prone to other illnesses. It is critical to ensure your horse is adequately hydrated year-round, during times of stress, harsh weather, and times of intense exercise.

Featured Image:

Courtnee Morton, DVM


Courtnee Morton, DVM


Dr. Courtnee Morton is a 2017 Ross University School of Veterinary Medicine graduate. Since graduation, she completed an equine internship...

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