The Dangers of Dairy. What Happens When a Lactose Intolerant Cat Drinks Milk

What is lactose intolerance in cats?

Lactose intolerance in cats is the inability to properly digest lactose, a sugar found in milk and dairy products (source). Lactose requires an enzyme called lactase to be broken down and absorbed by the body. When a cat doesn’t produce enough lactase, the undigested lactose can cause gastrointestinal upset.

The prevalence of lactose intolerance in cats is extremely high, with over 90% of cats being affected to some degree after weaning (source). Lactose intolerance develops as cats mature because they begin producing less of the enzyme lactase which is needed to digest lactose. Whereas kittens are able to tolerate milk from their mother, adult cats lose this ability as they age.

The underlying cause of lactose intolerance in cats is a decrease in lactase production. Lactase is naturally present in young kittens to help them digest their mother’s milk. However, as cats mature, their bodies begin producing less lactase since milk is no longer a staple part of their diet. This lactase deficiency prevents cats from properly breaking down and absorbing lactose sugars.

Symptoms of lactose intolerance in cats

Cats who are lactose intolerant will often experience gastrointestinal upset after consuming dairy products like milk. The most common symptoms include:

Diarrhea – One of the classic signs of lactose intolerance is loose, watery stool that can develop within a few hours after a cat drinks milk. According to CTVSH, diarrhea will occur within 8-12 hours if a lactose intolerant cat drinks milk.

Vomiting – Frequent vomiting is another common symptom of lactose intolerance in cats. The vomiting often starts shortly after consuming milk or other dairy products.

Gas – The undigested lactose in the intestines can lead to excessive gas production and flatulence in lactose intolerant cats.

Abdominal pain – The gas and diarrhea associated with lactose intolerance can cause abdominal cramping and discomfort in cats.

Bloating – Some lactose intolerant cats may experience a distended, bloated abdomen after drinking milk due to gas and inflammation in the digestive tract.

Effects of drinking milk for lactose intolerant cats

The effects of drinking milk for lactose intolerant cats can be quite severe. Within 8-12 hours of ingesting milk, lactose intolerant cats will exhibit symptoms like diarrhea, vomiting, gas, and abdominal cramping (1). The severity of these symptoms depends on the individual cat and amount of milk consumed. Some cats may only experience mild gas or loose stools, while others can develop profuse, watery diarrhea leading to dehydration.

More severe cases of milk ingestion in lactose intolerant cats can cause painful gastric distress and inflammation of the intestines (2). The diarrhea and vomiting can last upwards of 24 hours, causing lethargy, appetite loss, and weight loss. Dehydration from fluid loss is one of the biggest risks, which can become life-threatening if left untreated. Secondary health issues like pancreatitis may also develop.

The recovery time for a lactose intolerant cat will depend on the severity of the reaction. Mild cases may resolve within 12-24 hours as the milk passes through the digestive system. More severe cases with diarrhea, vomiting, and dehydration can take 48-72 hours to fully recover with veterinary treatment (3). Providing supportive care with fluids, anti-nausea medication, probiotics, and a bland diet can help the intestines heal and return to normal function.



Diagnosing lactose intolerance in cats

The major way of diagnosing lactose intolerance in cats is through a medical history and an elimination diet. The cat’s owner will want to provide a full medical history to the vet, describing when symptoms started and what they have observed after the cat consumed milk or other dairy products Why Cats and Cow’s Milk Don’t Mix. The vet will look for a pattern of gastrointestinal upset that occurs shortly after milk consumption.

An elimination diet involves removing all lactose from the cat’s diet for 2-3 weeks. The cat should only eat protein sources that do not contain lactose during this time, such as lamb, chicken, rabbit, venison or fish. The vet will monitor the cat’s symptoms during the elimination diet. If the symptoms resolve once lactose is removed, it confirms lactose intolerance Diagnosis and management of food allergy in dogs and cats.

There are also lab tests that can diagnose lactose intolerance in cats. This may involve a blood test, breath hydrogen test or stool acidity test. However, the elimination diet is usually sufficient to diagnose the condition.

Treating lactose intolerance in cats

The main form of treatment for lactose intolerance in cats is adjusting their diet. Since lactose, a sugar found in milk and dairy products, is the culprit behind the digestive issues, eliminating lactose is key. There are several dietary changes and supplements that can help manage lactose intolerance in cats:

Dietary changes:

– Switch to a lactose-free diet by removing milk, cheese, ice cream and other dairy products. There are commercial cat foods formulated to be lactose-free for cats with sensitivities. According to KittyBiome, diets low in lactose help reduce gas, diarrhea and other symptoms.

– Offer lactose-free milk designed for cats, which still provides nutrients without the lactose. Brands like Whiskas make lactose-free milk that many cats enjoy.

– Feed wet cat food, as the canning process helps reduce lactose levels compared to dry kibble. Feeding wet food may ease digestion.


– Probiotics help promote healthy gut bacteria and aid digestion. Products like Pro-Pectalin provide digestive enzymes.

– Prebiotic fiber supplements support digestion and gut health in lactose-intolerant cats.

In more severe cases, vets may prescribe medication to manage vomiting, gas, diarrhea or dehydration while transitioning to a lactose-free diet. With proper treatment, most cats with lactose intolerance can live long, healthy lives.

Preventing reactions in lactose intolerant cats

There are several ways to prevent reactions in lactose intolerant cats.

The most straightforward approach is avoiding dairy products altogether. Eliminating milk, cheese, yogurt, and other dairy from a cat’s diet ensures there is no lactose present that could cause an adverse reaction (Source: A lactose-free diet is the simplest way to prevent symptoms.

If some dairy is introduced, it should be done carefully in very small amounts. Adding tiny portions of milk or yogurt to a cat’s food and monitoring for reactions can help determine tolerance levels. Start with just a teaspoon and increase slowly over several days if no symptoms occur (Source: Gradual, monitored introductions with small amounts allows cats to adjust and will minimize risk of reactions.

Overall, avoiding dairy products is the most reliable approach. But for cats that may tolerate small amounts, gradual introductions can help prevent adverse reactions while still allowing some dairy in moderation.

Lactose-Free Diet for Cats

Cats with lactose intolerance will need to avoid dairy products and follow a lactose-free diet. Here are some tips for transitioning your cat to a lactose-free diet:

Ingredients to avoid:

  • Milk – Do not give your cat cow’s milk or any dairy-based milk. Milk contains lactose which cats cannot digest properly.
  • Cheese – All dairy cheeses contain lactose so should be avoided.
  • Yogurt – Even yogurt made from lactose-free milk will contain lactose and should not be fed to lactose intolerant cats.
  • Butter – Butter is made from cream so contains lactose.
  • Ice cream – All ice cream, even non-dairy kinds, contain some lactose so should be avoided.

Safe alternatives to dairy:

  • Meat-based baby food – Opt for baby food with meat like chicken, turkey or beef and without milk-based ingredients.
  • Broth – Low-sodium chicken or beef broth can be fed.
  • Lactose-free cat milk – Specialty lactose-free cat milk is available.
  • Water – The best drink for a lactose intolerant cat is plain water.

Tips for transition:

  • Gradually transition to lactose-free diet over 5-7 days.
  • Slowly replace lactose-containing foods with lactose-free alternatives.
  • If diarrhea occurs, temporarily feed a bland diet like boiled chicken and rice.
  • Once symptoms resolve, continue transition to lactose-free diet.

Outlook for Lactose Intolerant Cats

With proper management, the prognosis for lactose intolerant cats is excellent. By eliminating milk and other dairy products from the diet, symptoms can be completely prevented. Lactose intolerance does not negatively impact a cat’s lifespan or quality of life as long as the condition is properly managed.

Cats with lactose intolerance who are fed an appropriate lactose-free diet can live long, healthy, and happy lives just like any other cat. Their lactose intolerance will not get worse over time as long as they avoid consuming lactose. The condition is manageable and does not cause any long-term complications if dietary triggers are avoided.

The key to a good prognosis is owner education about proper diet and recognizing symptoms promptly if accidental lactose exposure occurs. With an appropriate lactose-free diet, supplements if needed, and owner diligence, lactose intolerant cats can thrive and experience excellent quality of life.

While lactose intolerance requires some dietary modifications, it is a manageable condition that does not have to negatively impact a cat’s health or longevity if properly controlled by the owner.

Caring for a lactose intolerant cat

Caring for a lactose intolerant cat requires some adjustments but is very manageable with the right care. Here are some tips for caring for a lactose intolerant feline:

Routine vet visits are important to monitor your cat’s health and ensure their lactose intolerance is not worsening. Your vet can recommend the best diet and supplements as needed (1).

Dietary considerations involve removing lactose sources like milk, cheese, and dairy products from your cat’s diet. There are many lactose-free cat food options available both wet and dry. Always check the label to ensure no milk products are included (2).

Supplements like probiotics and digestive enzymes can help improve digestion and reduce gas or diarrhea caused by lactose intolerance. Talk to your vet before starting supplements to ensure safety and proper dosage for your cat (3).

With some adjustments to their diet and care, most lactose intolerant cats can live happy and comfortable lives. Monitor their symptoms and work closely with your vet for the best health outcomes.


Myths about cats and lactose intolerance

There are some common misconceptions when it comes to cats and lactose intolerance. Many people believe that it’s perfectly normal and safe for cats to drink cow’s milk, but this is actually a myth. According to one article from Four Paws (, the truth is that most cats are lactose intolerant. Cats typically only produce enough of the enzyme lactase, which breaks down the sugar in milk, when they are nursing kittens. Once cats are weaned, they no longer produce much lactase and struggle to digest lactose.

Another myth is that it’s fine for kittens and young cats to drink milk, even if adult cats shouldn’t. But kittens also have trouble digesting lactose once they are weaned from their mother’s milk, usually around 8 weeks old. An article from CTVSH ( explains that lactose intolerance is normal in both young and adult cats. Feeding milk to kittens or cats of any age can lead to digestive upset.

While a small percentage of cats may retain some lactase enzymes into adulthood, the majority do not. It’s best to avoid giving your cat cow’s milk regardless of their age. Stick to commercial kitten formula for young kittens, and water or wet cat food for adult cats. Separating fact from fiction can help keep your cat healthy and avoid gastrointestinal issues.

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