Top 10 Signs of Dehydration in Horses, How to Prevent & Treat

Your horse finishes a training session on a 35°C day, sweat coating its neck and flanks. But an hour later, they're still not drinking. Should you be worried?

Dehydration and electrolyte imbalance in horses are closely connected, and recognising the early signs of electrolyte imbalance in horses can prevent serious health consequences. When horses sweat, they don't just lose water, but critical minerals like sodium, chloride, potassium, calcium and magnesium at high concentrations. Without these electrolytes, your horse's thirst response actually decreases, creating a dangerous cycle of worsening dehydration.

Key Takeaways

• Dehydration and electrolyte loss go hand-in-hand. Horses can lose 10-15 litres of sweat per hour during work.
• Early signs of electrolyte imbalance in horses include tacky gums, decreased skin elasticity, and poor performance.
• Simple at-home tests (skin pinch, capillary refill) can detect dehydration before it becomes critical.
• Prevention centres on providing electrolytes for horses, salt supplementation, and unlimited fresh water.
• Severe cases require immediate veterinary intervention with IV fluids.

How Dehydration Affects Electrolyte Imbalance

Here's what many horse owners don't realise: drinking plain water alone won't correct dehydration if your horse has lost significant electrolytes through sweat. Sodium is needed to hold water in body tissues, and is often lost in large quantities when sweating. Without adequate sodium levels, your horse's brain won't trigger the thirst response even when they're severely dehydrated.

During moderate exercise in warm weather, a horse produces around 5 litres of sweat per hour. In hot, humid conditions or during intense work, this can jump to 10-15 litres per hour. Each litre of sweat contains approximately 3-4 grams of sodium – losses that must be replaced to maintain hydration and performance.

Top 10 Signs of Electrolyte Imbalance in Horses

1. Tacky or Dry Gums: Healthy gums should be pink, moist and slippery. Dry, sticky gums indicate dehydration.
2. Prolonged Skin Tent: Pinch the skin on your horse's neck. If it takes longer than 2 seconds to snap back, your horse is likely dehydrated.
3. Slow Capillary Refill: Press your horse's gum until it blanches white, then release. Colour should return within 2 seconds. Any longer indicates dehydration.
4. Lethargy & Weakness: Dehydrated horses appear tired, unfocused and reluctant to work.
5. Decreased or Dark Urination: Reduced urine output or dark, pungent urine signals fluid loss.
6. Elevated Heart Rate: A resting heart rate above 60 beats per minute (normal is 25-40) can indicate dehydration.
7. Poor Performance: Fatigue, slower recovery times and reluctance to work often stem from fluid and electrolyte deficits.
8. Muscle Stiffness or Cramping: Particularly noticeable during stretching, this can progress to muscle disorders, such as tying-up, in severe cases.
9. Thumps (Synchronous Diaphragmatic Flutter): Visible twitching of the flanks in sync with heartbeat, caused by severe electrolyte imbalance affecting calcium and magnesium levels.
10. Sunken Eyes: Advanced dehydration causes eyes to appear dull and recessed.

How to Check Your Horse's Hydration Status

Perform these checks regularly during your grooming routine to determine what's normal for your horse.

Keeping Your Horse Hydrated and Balanced

The signs of electrolyte imbalance in horses are far easier to prevent than treat. Here's your prevention toolkit:

Daily Salt Supplementation

Provide 30-50 grams (2-3 tablespoons) of salt daily for horses in light to moderate work. Horses in heavy work during hot weather may need up to 170 grams.

Electrolyte Supplementation

Use quality electrolytes for horses during hot weather, heavy training, competition or transport. Look for products with high sodium and chloride content, minimal sugar (under 5%), and balanced potassium.

Unlimited Fresh Water

An average 500kg horse drinks 30-50 litres daily, increasing to 120-250 litres in hot weather. In winter, use tank heaters to prevent freezing and encourage drinking.

Diet Considerations

Haylage and fresh grass contain significantly more moisture than hay, up to 50% more. Consider soaking hay or offering wet feeds for horses prone to dehydration. Ensure adequate horse vitamin supplements to support overall health and mineral balance.

Treatment Options When Dehydration Strikes

Mild to Moderate Dehydration

• Offer fresh water and electrolyte solutions immediately
• Move horses to the shade and allow rest
• Monitor closely for improvement within 1-2 hours

Severe Dehydration

• Requires immediate veterinary intervention
• May need nasogastric tube fluids or IV therapy
• Can take 24-48 hours for full recovery
• Often indicates underlying issues requiring professional diagnosis

When to Call Your Vet

• Skin tent persists longer than 4 seconds
• Horse refuses to drink despite access to water
• Signs of colic (pawing, looking at flanks, rolling)
• Thumps, muscle tremors or tying-up
• No improvement after 2 hours of rest and water access

Protect Your Horse's Performance and Well-being

Understanding the signs of electrolyte imbalance in horses lets you act quickly when dehydration is a risk. Whether you're managing performance horses through competition season or caring for breeding stock through Australian summers, proper hydration management is non-negotiable.

At Scone Equine Group, we support horse owners with veterinary-backed guidance and quality electrolyte supplements designed for Australian conditions. Early recognition and prevention of dehydration keep your horses healthy, performing at their best, and ready for whatever challenges you face together.