Pet Hydration Guide: Water Intake Needs for Dogs and Cats

What Are the Daily Water Needs for Dogs and Cats?

Dogs typically need 50-60ml of water per kilogram of body weight per day. A 20 kg Labrador needs approximately 1-1.2 litres daily. Cats need around 40-60ml per kg, so a 4 kg cat needs 160-240ml daily. These are baseline amounts; actual needs increase with exercise, hot weather, lactation, illness, and dry food diets.

Pets fed primarily wet food receive significant moisture from their diet (wet food is 75-85 percent water) and may drink noticeably less from their bowl. This is normal and not a sign of dehydration. Pets on dry food diets need to drink more to compensate for the low moisture content (8-10 percent) of kibble.

Monitor your pet’s water intake by noting how much you refill the bowl daily. Sudden increases in drinking (polydipsia) can indicate diabetes, kidney disease, Cushing’s disease, or urinary tract infections and should be reported to your vet. Sudden decreases may indicate nausea, pain, or difficulty accessing water. Any significant change warrants veterinary attention.

What Are the Signs of Dehydration in Pets?

Dehydration occurs when a pet loses more fluid than it takes in, through illness (vomiting, diarrhoea), insufficient drinking, excessive heat, or increased urination from medical conditions. Signs include dry or tacky gums (healthy gums should be moist and slippery), loss of skin elasticity (gently pinch the skin on the back of the neck; in a hydrated pet, it snaps back immediately; in a dehydrated pet, it returns slowly), sunken eyes, lethargy, and concentrated, dark-coloured urine.

Mild dehydration can be addressed by encouraging drinking and, if the pet is eating, adding water to their food. Moderate to severe dehydration is a veterinary emergency requiring intravenous or subcutaneous fluid therapy. Do not wait for severe signs; if your pet has been vomiting or having diarrhoea for more than 24 hours, or if they refuse to drink for more than a day, contact your vet.

Puppies, kittens, senior pets, and those with chronic health conditions are at higher dehydration risk. Monitor these groups more closely, particularly during warm weather, illness, or after anaesthesia. For seasonal hydration advice, see our seasonal care calendar.

How Should You Encourage Your Pet to Drink More?

Cats are notoriously reluctant drinkers, an evolutionary trait from their desert-dwelling ancestors. Strategies to increase cat water intake include: providing a pet water fountain (many cats prefer running water), placing multiple water bowls in different locations, using wide shallow bowls (cats dislike their whiskers touching the sides), ensuring water is fresh and changed daily, and adding a small amount of tuna water or low-sodium chicken broth for flavour.

For dogs, ensure water bowls are always accessible, clean, and filled with fresh water. Some dogs prefer cold water; adding ice cubes in summer can encourage drinking. Travel with water and a portable bowl during walks and car journeys. Dogs that exercise heavily may need electrolyte supplementation; consult your vet about canine-specific electrolyte products for very active dogs.

Feeding wet food is the single most effective way to increase total fluid intake, particularly for cats. A cat eating 200g of wet food daily receives approximately 150-170ml of water from the food alone, often meeting the majority of their daily needs. If your cat is reluctant to drink and on a dry-only diet, transitioning to wet food or adding water to kibble can significantly improve hydration status.

What Is the Water Quality and Safety?

UK tap water is safe for pets in almost all areas. Filtered or bottled water is not necessary unless your local water has specific issues. Some pets prefer the taste of filtered water, and if using a pet fountain, follow the manufacturer’s filter replacement schedule to maintain water quality.

Outdoor water sources carry risks. Stagnant ponds, puddles, and slow-moving streams can harbour Leptospira bacteria (causing leptospirosis in dogs, a serious and potentially fatal disease covered by vaccination), blue-green algae (cyanobacteria, which produce toxins fatal to dogs), and parasites. Discourage pets from drinking from puddles, particularly in urban areas where antifreeze contamination is possible. Carry fresh water on walks.

Shared water bowls at parks, pet shops, and cafes carry a risk of disease transmission. While the risk is low, immunocompromised pets, puppies, and unvaccinated animals should use their own water supply. If you are concerned, carry a collapsible travel bowl and fresh water for your dog during outings.

What Are the Hydration and Health Conditions?

Several common health conditions affect hydration. Kidney disease (one of the most common conditions in senior cats) causes increased urination and thirst as the kidneys lose the ability to concentrate urine. Diabetes mellitus causes similar symptoms. Cushing’s disease in dogs increases thirst and urination. In all these conditions, restricting water access is harmful; always allow unlimited access to fresh water and report increased drinking to your vet.

Vomiting and diarrhoea are the most common acute causes of dehydration. Withhold food for 12-24 hours for adult dogs with mild vomiting (not puppies), but always maintain water access. If vomiting prevents water retention, your vet may need to provide fluids subcutaneously or intravenously. Diarrhoea lasting more than 48 hours, or accompanied by blood, lethargy, or refusal to eat, requires veterinary attention.

Post-surgical pets and those recovering from illness often need encouragement to drink. Warming water slightly, offering ice chips to lick, and using flavoured water (tuna juice, broth) can help. Your vet may provide subcutaneous fluids for pets at home if ongoing hydration support is needed, a common practice for cats with chronic kidney disease in the UK.