Dehydration in Cats

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  • What is dehydration?

    Dehydration (hypohydration) is a severe and potentially life-threatening condition that is defined as excessive loss of water and electrolytes (minerals such as sodium, chloride, and potassium) from the body.

    Most animals are made up of around 60% water. When the water ratio falls 5% below normal, cats will start to show signs of dehydration.

    Kittens, senior cats and cats with underlying medical conditions are at increased risk from dehydration.

    Dehydration has three classes:

    • Mild dehydration: up to 5%
    • Moderate dehydration: 6 – 10%
    • Severe dehydration: 11% or more

    Causes of dehydration in cats

    Dehydration can develop due to decreased water intake and/or increased output (urine, vomiting, diarrhea). Dehydration requires veterinary attention immediately. Failure to do so may result in death.

    • Sickness – Any sickness which results in a loss of appetite and thirst can lead to dehydration
    • Increased urination – Medical conditions such as diabetes and kidney disease in which the cat urinates more often, leading to excess fluid loss
    • Vomiting and/or diarrhea
    • Blood loss
    • Shock
    • Fever
    • Heatstroke
    • Lack of available, fresh drinking water

    Clinical signs

    • Sunken eyes
    • Dry, tacky gums
    • Poor skin elasticity
    • Lethargy
    • Increased heart rate
    • Poor capillary refill time
    • Loss of appetite
    • Increased or decreased water intake
    • Constipation. Water is reabsorbed from the colon, and if the cat is dehydrated, the body will try to conserve water by removing additional water from the stool

    How to check a cat for dehydration

    Skin turgor test (skin tenting): Grasp some skin at the scruff of the neck and gently pull it up to form a tent. The skin will spring back immediately (as you can see in the video) in a well-hydrated cat. The skin will be slower to retract if the cat is dehydrated and the more severe the dehydration, the slower the skin will take to retract.

    Capillary refill time: This helps you to test your cat’s blood circulation and can indicate dehydration, heart failure or shock. To check capillary refill time life your cat’s upper lip and press the flat of your finger against the gum tissue. Remove the pressure, and you will see a white mark on the gum where your finger was. Using a watch with a second hand, time how long it takes for the pink colour to return to the white spot.

    • 1-2 seconds is normal
    • 2-4 seconds is moderate to poor
    • > more than 4 seconds is an emergency
    • < less than 1 second is an emergency


    Diagnosis of dehydration is relatively easy to diagnose based on symptoms and performing the skin turgor test.

    Diagnostic workup:


    The goal is to treat the underlying cause as well as replace fluids, which may include:

    • Medications to treat vomiting and/or diarrhea.
    • Fluid replacement therapy either intravenous or subcutaneous.

    In some cases, you may be asked to give your cat fluids subcutaneously at home, which is a relatively straightforward procedure in which the carer administers fluid under the loose skin at the back of the neck. The veterinarian will supply needles and syringes as well as fluids. This is useful for cats who has an underlying medical condition such as diabetes.


    Medical conditions, in particular, chronic kidney disease increase the risk of dehydration. Pet owners must be diligent in ensuring cats remain well hydrated and closely monitor for signs of dehydration.

    • Ensure there is a constant supply of fresh, clean drinking water available at all times.
    • Cats don’t like to drink from dirty bowls, which can form a sticky biofilm if unwashed. This biofilm can contain several potentially dangerous bacteria. Wash water bowls once a day and water every 2-3 days in hot soapy water and rinse well.
    • Provide your cat with a cool, sheltered area if it has access to the outdoors.

    Seek veterinary attention for cats with vomiting or diarrhea or if you notice an increase in the cat’s thirst and urination.

    How to get more fluids into a cat

    Some cats can be fussy when it comes to water; if you need to get more fluids into them you can try the following:

    Switch to wet food: Domestic cats are descendants of desert-dwelling animals who obtained most of their water via their diet. Dry food only contains 10% water, compared to 70% in canned or raw food. Many cats don’t make up the shortfall by drinking more water.

    Encourage the cat to eat: If he is reluctant to eat, try feeding him strong-smelling foods such as tuna. Warm it slightly in the microwave which can make it smell stronger.

    Provide fresh drinking water: Make sure you change your cat’s water at least once a day and wash the cat’s bowl which can develop smells. If you have multiple cats, think about adding additional water bowls.

    Buy a cat water fountain: Some cats prefer running water.

    For more information on how to get cats to drink more water, read here.


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio