Is Milk Bad For Cats?

Since all 4 of my cats love drinking milk, I started wondering if this cat and milk incompatibility was a reality or just a myth.  And I decided to do some background research to find out the truth about all types of milk and cats.

So here’s the scoop: Is milk bad for cats to drink? Milk is bad for cats if the cat is lactose intolerant.  Some adult cats are not lactose intolerant, making milk safe for them to drink.  However, most adult cats are lactose intolerant where drinking milk can cause an upset stomach, vomiting, and diarrhea.

This can be dangerous for your cat’s health, depending on the severity.

Red fluffy cat drinking milk from yellow bowl in the countryside

I was shocked to hear that most cats are lactose intolerant!  

Especially since kittens need milk to grow.

I’ll be much more careful now.  

But there is good news, too.

My cats love drinking milk, so I was relieved to discover that there’s a way I can still give them the delicious drink without risking those awful side effects, you just have to be careful of what type of milk you set out.

Cats And Milk Myth: Why is milk bad for some cats? 

While it may seem like a myth at first, there’s actually a scientific reason hiding behind it all.  

You may have heard about lactose intolerance in people, but it’s actually very common in cats.  

Having lactose intolerance means that the digestive system is unable to digest lactose, making any food with lactose problematic.

Lactose is a type of chemical compound that is classified as a sugar.  

Since it’s found in milk, lactose is commonly referred to as a ‘milk sugar’.  

This particular type of sugar consists of the units called galactose and glucose, and it’s responsible for giving milk its sweet flavor.  Lactose is a small (2-8%) component that is naturally found within milk.

Lots of people feed milk to their cats without even thinking twice about it. Below is a quick explanation:


Here’s where things can get a little tongue-twisted, so hang on!  

In order to digest lactose, the digestive system must possess lactase, which is an enzyme produced by the small intestine.  

Lactase breaks down lactose, the milk sugar, and allows it to digest properly in the body.

When a cat (or person, for that matter) is lactose intolerant, this means that their body does not produce the amount of lactase necessary for smoothly digesting lactose.  

In other words, a cat that is lactose intolerant can’t digest milk!

This may seem kind of silly, considering that kittens survive on milk when they’re first born.  

But just because a kitten drinks milk, doesn’t mean that it won’t become lactose intolerant as a cat!  

In fact, the only time that cats are exposed to lactose (the milk sugar) in the wild is when they’re first born and rely on milk from their mother.

It’s important to note that the body changes and develops over time.  

Kittens naturally produce the enzyme needed to break down the lactose in milk so that they can get the essential nutrients to develop properly.  

As a kitten grows into an adult cat, the feline digestive system changes, producing less lactase.

As this change occurs, the cat becomes lactose intolerant.

Most adult cats are lactose intolerant.  

For those felines, milk is bad because the digestive system isn’t equipped to handle the lactose contained.  

Therefore, milk is bad news, because it puts unnecessary stress on the feline digestive system, resulting in some pretty unpleasant consequences.

What happens if a cat drinks milk?

Cats are curious creatures, so it’s no surprise that they typically like tasting milk.  

Not to mention, they probably enjoy the sweetness of milk—which is ironic, because this is the very thing that causes issues for those cats that are lactose intolerant!

It’s important to remember that not all cats are lactose intolerant, though.  

Some cats are perfectly capable of drinking and digesting milk without an issue.  For these lucky few felines, you’ll notice that not too much happens after they enjoy a saucer of milk.

Below is a visual of what milk does to cats:


For those cats that do express a lactose intolerance, the side effects are very noticeable.

You can expect most side effects to pop up within 12 hours of the cat drinking milk, so it’s important to pay very close attention to your cat’s behaviors during this window of time.  

If more than a day has passed after your feline has indulged in milk and you haven’t observed any side effects, then it’s safe to say that your cat is in the clear.

Because lactose intolerance is directly linked to the digestive system, all of the side effects of drinking milk are related to the feline’s digestive system, too.  

One side effect can be a simple stomach discomfort. While this consequence can be tricky for humans to identify, it can be quite painful for the cat.

More severe side effects include vomiting and diarrhea.  

Remember, lactose intolerance means that the digestive system cannot process the milk sugar correctly, so the body’s way of dealing with this is to purge the milk.

In addition to being uncomfortable for the cat, vomiting and diarrhea can be quite a nuisance for the pet owner, too.

Particularly if the cat spends most of the time indoors.  

You might want to keep your brand new furniture in mind the next time you consider passing your leftover cereal bowl over to the furry feline!

All joking aside, these two side effects go far beyond discomfort and inconvenience.  

Severe vomiting and diarrhea can cause dehydration.

Essentially, the cat’s body is telling it to get rid of those ‘bad’ ingredients (the milk sugar known as lactose) that it’s incapable of digesting.  

Ginger cat drinking milk from a cup

In many cases, additional fluids are lost.

In severe cases, this can put the cat at risk of becoming dehydrated—which opens a whole new jar of serious health consequences.

In reality, lactose intolerance stretches across a big spectrum, meaning there are different levels of intolerance possible.  

This means that the side effects can range in severity. Some cats may have a slight intolerance, meaning may only vomit after indulging in a large bowl of milk.  

Meanwhile, another cat may have a significant intolerance, and even just a few little sips of milk can trigger digestive issues.

Because there is a lot of variation, it’s important to watch your cat carefully when trying to determine his lactose intolerance.  

And remember—adult cats wouldn’t normally drink milk in the wild; domesticated cats only indulge because we offer it to them!

Are all types of milk bad for cats?

You might be thinking: “What a bummer. I have to cut milk from my cat’s diet now!”  

That was my first thought when I learned about lactose intolerance in cats.  

But then I started thinking: “Wait.  If people with lactose intolerance can drink other types of milk, then maybe cats can, too!”  And it turns out, that’s true!

Lactose intolerance is the main culprit for why most cats can’t drink milk without suffering the side effects.  

So if you remove the lactose, you remove the problem!

Lactose-Free Milk For Cats

There is actually lactose-free milk for cats products that are available in stores.  

And while they were designed to accommodate humans who are lactose intolerant, cat owners can happily buy this product for cats with the same digestive limitations.

I also looked into other milk alternatives that are popular in the human world:

  • Soy milk
  • Almond milk

While these options eliminate the problem of lactose, they really aren’t that beneficial for cats.

They may not have lactose, but they certainly carry other nutritional concerns.

In fact, some cats may be allergic to soy milk.  

For those that are, soy milk can trigger serious skin issues, similar to an allergic reaction.  

Also, soy milk usually has added sugars to improve its flavor for humans, and these extra sugars aren’t very healthy for cats.  

Plus, soy is vegetable based, meaning it’s not a natural part of a feline’s diet in the wild—cats are carnivorous!

Can cats drink almond milk?

Almond milk doesn’t contain lactose but contains almond nuts. Stomach problems do stem from cats being sensitive to certain nuts.  Along with other milk products stemming from nuts, almond milk is not a natural part of a feline’s diet.  

Cat drinking milk from a saucer

These nut kinds of milk can cause real digestive issues, including:

  • Diarrhea
  • Vomiting

If your cat has a few sips of almond milk or soy milk out of curiosity, there’s no need to panic.  

A small intake of these products isn’t likely to cause serious health damage.

However, it’s not recommended to give these to your cat all the time or in large amounts.  

If they do get ahold of them, be sure to pay close attention for side effects.

What can cats drink?

So why do we feed milk to cats anyway?  It seems like cats and milk go together like any classic pairing—monkeys and bananas, dogs and bones, the sun and the moon.  

But this idea is like folklore.

It’s been passed on for so long that many people just assume that cats need to drink milk as a core dietary staple.

If your adult cat is one of the lucky few that doesn’t suffer from lactose intolerance, then milk isn’t likely to pose a huge health threat.  

Just like chocolate does if your cat eats it.

However, milk shouldn’t be the primary source of hydration for the cat. In other words, it’s okay to use as an occasional treat or in small quantities, but it shouldn’t be the sole liquid provided.

There’s a liquid that is much more important for your cat to rely on for hydration: water.  

Whether your cat is lactose intolerant or not, water is the most important thing you can provide for your cat to drink.  

This goes for all cats, wild or domesticated, lactose intolerant or not.

Water is essential for establishing a healthy diet because it does many things.  

First of all, water helps the cat digest solid foods.

This is important for getting all the nutrients out of meals, in addition to processing salt and electrolytes.  

Similarly, water helps the cat to eliminate waste and expel toxins from the body.

And finally, water helps the cat regulate its body temperature.

All of these elements are crucial for cultivating a healthy body.

calico cat drinking milk from a tea cup

To wrap it up, even if your cat can drink milk (because it isn’t lactose intolerant), it probably shouldn’t rely on milk as a main source of nutrition.  

Water is the best liquid to serve as part of a healthy, balanced diet for your cat.

Related Questions

Why do cats like milk?  Milk has a mild sweetness to it, which is due to the milk sugar component called lactose.  Cats typically enjoy this sweetness. While milk is not part of a natural diet in the feline world, domesticated cats may learn to like milk because it is habitually offered to them by pet owners.

Is milk good for cat constipation?  Adult cats that are lactose intolerant do not have the ability to digest milk.  This inability often results in vomiting and/or diarrhea. While this may seem like a solution to constipation, it is not a healthy method for relieving constipation because it puts unnatural stress on the digestive system.

Is milk bad for kittens?  While most kittens are able to digest cow’s milk better than adult cats, cow’s milk is not a good source of nutrients for kittens, due to whey and casein components.  The nutrients found in the milk of the kitten’s mother is most suitable for development. If this is unavailable, milk replacers that are sold in pet stores are the next best thing.

Can cats drink goats milk?  Raw goat’s milk is one of the most nutritionally complete food and cats can drink it.  It’s said that kittens without moms should be fed goats milk when their mother’s milk is available.

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