It is very normal to hear your cat purring while being petted. Cats purr when you pet them for several reasons. Primarily, it is a sign that they are enjoying their strokes with their favorite human, but purring can also be a sign of overstimulation or even stress. There is more behind the purr than most unassuming pet parents realize!
The best way to tell what your cat is communicating through its purr is to pay attention to other factors, such as body language. And a common combination observed by pet parents is simultaneous purring and shaking. So, why is my cat trembling while purring? Is this normal behavior? Or is this something to be concerned about?
I answer all of these questions and more in this article. If your kitty won’t stop trembling and quivering, you’ll want to keep reading to find the answers. In most cases, this shaking is simply the vibrations from their purrs. However, there are more serious potential causes all owners should be aware of…
Why is My Cat Trembling While Purring?
Purring and trembling go hand-in-hand, and the two are often observed together. Here are some possible causes for this behavior – read through each and see which you think applies. And if you’re at all concerned about your cat’s purring, don’t hesitate to call your vet for advice.
1. Extreme Happiness and Contentment
The first and most likely reason your cat is trembling and purring is that they’re extremely happy and content. As I’m sure you already know, cats purr when they are happy. It’s one of the main ways that cats show love and affection. When the petting feels good, they can’t help but let out a little purr!
The purring sound we hear is a vibration from the larynx, also known as the voice box. When your cat feels happy, the brain sends signals to the muscles in the larynx and causes them to vibrate at 25 to 150 vibrations per minute. This separates the vocal cords and causes the soothing purring sound we know and love. The diaphragm also moves up and down at the same pace.
The happier and more content your cat feels, the more signals the brain sends to the larynx muscles, and the faster they vibrate. Vibrating and purring to the max can cause your cat’s whole body to tremble. A similar comparison would be letting out a small giggle compared to a big old belly laugh – the belly laugh will make your body move and shake.
However, purring can also be a sign of overstimulation and stress. Therefore, the best way to discover the meaning of your cat’s purr is to look at other signs. Signals that your cat is purring due to happiness include your cat making biscuits, offering areas to be petted, and assuming a relaxed body position. If these signs aren’t clear, your cat might be trembling and purring due to stress instead.
2. Anxiety and Stress
Many people assume that a purring cat is a happy cat. However, cats also purr when feeling stressed. The vibrations are calming and healing, so cats use the power of the purr to help calm themselves back down. It’s part of their coping strategy when dealing with a situation causing them to feel scared.
Trembling is also a sign of stress in cats. This is a natural response of the autonomic nervous system as it prepares the body to enter its “fight or flight” response to best respond to the fearful situation. All the muscles in the body tense, and this increased tension is what can cause shaking.
Therefore, a combination of purring and shaking can signify stress and anxiety. Cats are very sensitive creatures, so it might not always be apparent what has caused them to feel anxious. In fact, it can be extremely difficult trying to figure out the cause, and their behavior can be unpredictable.
Below are some common causes of stress in cats that may apply:
- Rearranging furniture in the home or new furniture
- A new pet or baby entering the household
- Moving to a new home address
- Loud noises such as fireworks or construction
- An unfamiliar cat prowling the neighborhood
- Unfamiliar guests entering your home
- Competition from other cats in the household
- Changes to their normal feeding routine
- Inappropriate handling, often by children
- Lack of critical resources in the home
Thankfully, stressed cats act very differently from happy cats, so you can easily tell what your cat thinks by paying attention to its body language. If your cat is making biscuits and seems relaxed, they’re content, but if it looks tense and thumps its tail, it’s likely unhappy and stressed. Stressed cats are also much more skittish and tend to sleep more, eat less, and refuse to play.
The best way to deal with stress is to remove the object that is upsetting your cat. However, this is not always possible! In these cases, the best thing to do is to keep everything else as consistent as possible so your cat’s anxiety doesn’t worsen. They’ll eventually get accustomed to the change, but make sure you provide plenty of hidey-holes they can retreat to while they do so.
3. Irregular Body Temperature
For cats, a normal body temperature is considered anywhere between 100.5°F to 102.5°F. Anything below this range and your cat will be cold, potentially getting hypothermia. On the converse, anything above this range is usually the result of a fever bought on by some type of infection.
Shaking is often observed in both of these situations. When cats are cold, they start trembling and shivering to generate heat to help warm the body. Shaking also happens when cats have a fever. This is the body’s natural response as shivering again causes the body temperature to rise, which helps to fight off the virus of bacterial infection that’s making your kitty sick.
If your cat is trembling due to an irregular body temperature, it is unlikely that it will only shake while purring. However, there is a chance that you’ve only noticed it with your cat sitting on your lap. I suggest checking your cat’s temperature and helping them warm up or cool down, depending on the reading of the thermometer.
There are also other signs that your cat is struggling with its temperature. For example, is your cat drooling when purring, too? It is rare for cats to drool, which is usually a sign they’re too hot. Your cat might also stick to shaded areas if too hot or curl up next to the radiator when too cold. Panting, restlessness, and drowsiness are other signs.
4. Pain from Injury or Illness
Unfortunately, your cat’s trembling and purring could be caused by underlying medical conditions. Injuries and illnesses cause your cat pain. Cats are masters at hiding pain as they don’t want to appear vulnerable. However, purring and trembling is a subtle sign that your kitty is in discomfort.
Cats purr when in pain as the precise vibration frequency has therapeutic benefits. Vibrations between 25 and 50 Hz help to heal bones and promote the production of new bone cells, whereas vibrations over 100 Hz aid in healing soft tissue injuries. Endorphins are also released in the brain when your cat purrs, which further help with pain management.
Trembling is also commonly seen in sick or injured pets. This could be because your cat has a fever due to an infection. Alternatively, some conditions can lead to muscle spasms and shaking. Or perhaps the pain your kitty is feeling is causing them to become stressed, which – as I have already explained – activates the “fight or flight” response and causes trembling.
Other indications that your cat is in pain or distressed include:
- Purring and trembling without being stroked
- Cats purr when they sleep to help promote healing
- Acting more aggressive than usual, such as hissing and biting
- Hiding more than usual and being withdrawn
- Other clinical signs of illness, such as fatigue or loss of appetite
If you think your cat is trembling and purring in pain, take your furry friend to the vet. They need to be assessed and diagnosed as quickly as possible so that treatment can start.
5. Dreaming in REM Sleep
You might notice that your cat starts purring and shaking when sleeping. Rather than a constant trembling, you’ll observe more of a twitch. This is a sign that your cat is in rapid eye movement (REM), the stage in sleep in which dreaming occurs.
In this dreaming stage of sleep, there is a surge in brain activity as neurons (specialized brain cells) fire more than usual to form new neural connections. Some of these neurons misfire and accidentally send signals to the muscles. This causes random movements and involuntary muscle spasms, leading to twitching.
I often see my cat twitch in her sleep and love to imagine what my furry friend is dreaming about. When accompanied by purring, it’s almost definitely a good dream. Perhaps they’re imagining they’re running in the wild hunting mice. Or maybe they’re curled up on your lap, getting some kitty cuddles. There is no way we can know for sure, but I love making stories up in my head.
It is important to also distinguish between dreaming and seizures. Seizures when sleeping are extremely rare and are more likely to happen when your cat is falling in or out of sleep. Rather than twitching, their entire body will tense and shake uncontrollably. Call your vet immediately if you think your kitty is having a seizure instead of sweet dreams.
6. Low Blood Sugar Levels
The final reason your cat is trembling while purring is low blood sugar, also known as hypoglycemia. Cats rely on the sugar in their blood as a source of energy. When there is no energy available for your cat to use, muscle shaking and tremors are typical.
Low blood sugar can happen if your cat hasn’t eaten for an extended period. If it’s been hours since their last meal, your cat has probably used all the energy, and blood sugar levels drop. This can happen when cats refuse to eat due to certain illnesses. For example, dental diseases can make eating painful, so cats lose their appetite, stop eating, and experience a sugar crash.
Hypoglycemia is also more common in young kittens under three months old. When this young, kittens have not learned to regulate their blood sugar levels, so they can spike or drop suddenly. Cats with diabetes mellitus are also considered high risk. These cats cannot respond to or don’t have enough insulin, making it hard for them to regulate blood glucose.
If your cat has hypoglycemia, the shaking is not necessarily accompanied by purring. However, there is no reason why your kitty can’t do the two simultaneously! Putting a drop of honey on your cat’s tongue can help solve the issue, but your vet should still be consulted in case there is an underlying medical condition to blame for their low sugar levels.
MY FINAL THOUGHTS
As you have learned, the question “Why is my cat trembling while purring?” does not have a straightforward answer. In most cases, the trembling you see results from the purrs. Purring is caused by vibrations of the muscles in the voice box. When your cat purrs intensely, this can cause the entire body to tremble and shake!
However, cats also use purring as a coping mechanism when feeling stressed or in pain. The vibration frequency helps to calm your cat down and has therapeutic benefits for the body. Trembling is also likely in these situations, either as a result of “fight or flight” activation or as a result of the illness itself. Irregular temperature or dreaming are two other viable explanations.
Nevertheless, most cases of trembling and purring are nothing to worry about. Pay attention to your cat’s body language and assess for other symptoms and behavioral changes. If you notice anything concerning, call your vet. Your kitty might be perfectly happy and content, but it is always best to be safe and get them checked by a professional.