In the human world, hydration is often associated with sports drinks, electrolyte tablets and replacing the minerals lost through sweat.
Hydration is just as important for dogs, but we need to think about it a little differently.
Humans sweat to keep cool and can therefore lose large amounts of water and electrolytes during warmer weather or exercise. Dogs, on the other hand, rely heavily on panting to regulate body temperature. They still lose fluid trying to stay cool, but the route of loss is different.
So let's take a closer look at hydration and the role it plays in your dog's health, performance and ability to stay cool.
What Is Hydration?
In biological terms, hydration is the process of providing or absorbing liquid, specifically water, to maintain healthy bodily fluids and functions.
Water is the most abundant molecule in the body, accounting for around two-thirds of an adult dog's body weight. Every cell in the body depends on water. Without it, many of the processes we take for granted simply cannot occur efficiently. Water forms the basis of blood, lymph, digestive secretions and the fluid found inside and outside cells. Through these fluids, nutrients can be delivered to tissues, waste products can be removed, hormones can reach their targets and cells can maintain their normal function. Water underpins virtually every physiological process in the body.
Hydration, Circulation and Thermoregulation
One of water's most important roles is supporting circulation.
Water helps maintain blood volume, allowing the cardiovascular system to circulate blood efficiently around the body. This supports the delivery of oxygen and nutrients to tissues, the removal of carbon dioxide and metabolic waste products, and the transport of heat.
This final role is particularly important when it comes to temperature regulation. Every day, your dog's body generates heat through normal metabolism, with heat production increasing substantially during exercise. Before heat can leave the body through cooling mechanisms such as panting, it must first be transported away from where it is produced. Adequate hydration helps maintain the blood volume needed for this process.
Hydration status also influences how hard the cardiovascular system must work. As fluid losses accumulate, plasma volume begins to fall and blood becomes more concentrated. The cardiovascular system must work harder to maintain blood flow, particularly during exercise or hot weather when demands on the body are already elevated.
When hydration begins to decline, thermoregulation becomes more challenging. With less fluid available for circulation, the body must work harder to transport heat and maintain a stable temperature.
Every Pant Removes More Than Heat
Panting does remove heat, but every breath also removes water.
During periods of exercise, excitement or warm weather, these losses can accumulate surprisingly quickly. Dogs may also lose additional fluid through saliva, particularly when panting heavily for prolonged periods.
In other words, the very mechanism that helps dogs stay cool increases their need for water.
But It's Not Just Water
Water is the foundation of hydration, but body fluids also contain dissolved minerals known as electrolytes. Electrolytes such as sodium, chloride, potassium and magnesium play important roles in fluid balance, nerve signalling and muscle function.
Unlike humans, dogs don’t lose large amounts of electrolytes through sweat. However, electrolytes are continuously lost through urine as part of normal physiological regulation. In addition, during exercise and periods of heavy panting, additional losses can occur through saliva. Studies in exercising sled dogs have shown that saliva contains electrolytes such as sodium, chloride and magnesium, and that salivary electrolyte concentrations can change during periods of training and exercise. For healthy dogs eating a nutritionally dense diet, these losses are generally replaced through normal feeding. However, periods of increased activity, prolonged exercise or hot weather can place greater demands on both hydration and nutrition. This highlights the value of providing fluids and foods that support hydration while also contributing useful nutrients. Although water remains the foundation of hydration, nutrient-rich additions can complement a dog's overall hydration strategy.
When Hydration Isn't Quite Optimal
Hydration isn't just a question of whether a dog is dehydrated or not. There is a spectrum between optimal hydration and clinically significant dehydration.
For active dogs, even relatively small fluid losses can influence how the body performs and responds to exercise. One of the first systems to be affected is thermoregulation. With less fluid available to support circulation, the body may have to work harder to transport heat and maintain a stable temperature. For working and sporting dogs, this may result in subtle changes in performance rather than obvious signs of illness. A dog may tire more quickly, recover more slowly between runs, or appear less willing to maintain the same intensity of work. Handlers may also notice changes in focus, responsiveness or decision making, particularly during prolonged activity or warm weather. While many factors influence performance, hydration is one piece of the puzzle that is often overlooked.
Whilst you of course want to prevent dehydration, the more nuanced goal of a hydration strategy is to support the physiological systems that allow dogs to perform, recover and regulate body temperature effectively.
Why Thirst Isn't Always Enough
Many owners assume that access to water is all a dog needs to stay hydrated, but it's not always that straightforward. Working, sporting and highly motivated dogs can become so focused on activity that they don’t always stop to drink. Travel, competition, excitement and unfamiliar environments may also influence drinking behaviour. By the time obvious signs of dehydration appear, performance, recovery and temperature regulation may already be under greater strain. This is why taking a proactive approach to canine hydration is so important.
Looking Ahead
Understanding why hydration is important is only part of the story. In the next article, we'll explore why access to water doesn't always guarantee adequate hydration, and what the research tells us about encouraging dogs to drink more.
Lisa Hannaby-Aird
A Registered Associate Nutritionist and author of Nutrition for Dogs, Lisa combines expertise in nutrition, psychology, biochemistry, and neuroscience to help dog owners understand the science behind canine health, behaviour, and nutrition.