Cat lovers often hear stories about obesity in cats, but you may have found yourself concerned about your pet’s weight for a totally different reason. Have you ever wondered if your cat is dangerously underweight? If you believe that your cat is underweight and you’re searching online for more information on how to put weight on a cat, then this guide will be invaluable. However, in some cases a cat may be underweight because of an underlying health condition. In this article, I’ll go over the different health issues that can lead to weight loss in cats, while exploring the different options you can try that can help your cat pack on the pounds.

cat on a weighing scale

Cat Weight Loss Issues that Require Your Attention

A healthy weight for your cat will depend on their overall health, activity level, breed, and age. On average, an indoor cat weighs around nine to ten pounds. However, some breeds may weigh significantly less, even once they have reached adulthood. On the other hand, there are also breeds that can easily weigh up to eighteen to twenty pounds. For most felines, you should be able to feel their backbone and ribs when you run your hands over their body, but you shouldn’t be able to see them.

If you can feel and see their ribs, or you’re not sure if your cat needs to gain weight,  make an appointment with your vet for an exam to rule out any health problems. A veterinarian will determine if your cat needs to gain weight based on their body weight, size, and age and how much weight gain is necessary.

Feline Health

A healthy cat usually maintains the same weight year after year, although it’s not uncommon for weight gain to occur when they’re seniors. If you have a younger cat who is losing weight, they may be suffering from an underlying health condition. At a veterinarian  appointment, they will check for gastrointestinal issues, such as:

  • Pancreatitis
  • Constipation
  • Diarrhea
  • Gastroenteritis

A veterinarian may need to run some tests on a stool sample to determine exactly what’s going on and what the problem is.

Rapid weight loss in cats can also be contributed to:

Internal Parasites

These parasites can commonly be found in cats that are otherwise healthy and make it almost impossible for a cat to gain weight. A parasite can be a single-cell microscopic organism or wormlike.

Wormlike parasites can include:

  • Tapeworms
  • Hookworms
  • Roundworms

Microscopic organisms include:

  • Giardia
  • Isospora

If parasites are ruled out, a vet will check a cat’s mouth for any dental issues.

Dental Disease

Aging cats, just like humans, are prone to dental disease. Sore gums and teeth are likely to put your cat off their food, especially if there’s an impaction or abscess. Your veterinarian can resolve any dental issues at another appointment, where the cat will need to be put under anesthesia for the necessary treatment.

If your pet’s oral health is fine, then their thyroid hormone levels may need to be checked.


An overactive thyroid is very common in older cats and is caused by the overproduction of thyroid hormones. Your veterinarian can prescribe medication that can help regulate hormone levels.

Symptoms of an overactive thyroid can include:

  • Rapid weight loss
  • Vomiting
  • Increased appetite
  • Restlessness


weighing a cat

Diabetes is another condition that’s often seen in seniors. Diabetes has many symptoms that are similar to that of an overactive thyroid gland, such as rapid weight loss and an increased appetite. Many cats will also have increased urination and increased thirst. Depending on the severity of the condition, your veterinarian may need to prescribe insulin and have you check your cat’s blood sugar levels several times a day. This is the best way to manage diabetes.

Kidney Disease

Another common cause of weight loss in seniors is kidney disease. The symptoms linked to this condition also include increased urination and excessive thirst. A cat may also experience diarrhea, vomiting, and bloody urine.


Cancer is the number one cause of death in cats. If a cat is losing weight rapidly, this can be a sign of a gastrointestinal tumor.

Visual impairment and Arthritis

An older cat may have trouble making it to their food bowl, especially if they have arthritis or a visual impairment.

Loss of Sense of Smell

If your pet’s sense of smell isn’t as good as it used to be, they may suffer from a lack of appetite and loss of enjoyment eating.


It’s possible that a medication your cat is taking has impacted their appetite. Speak to their vet before you stop the medication or change the dose.

Other Causes of Weight Loss in Cats

underweight cat on scale

A cat may have digestive issues or food allergies that are causing them to lose their appetite. If your cat is experiencing abdominal discomfort, they may refuse to eat. Other reasons why a cat may be experiencing a lack of appetite include:

You Changed Cat Foods

If you have recently introduced a new pet food or kitten food to your kitty without making the gradual switch from the old food to the new food, your cat may be struggling with bloating, diarrhea, gas, nausea, and vomiting. A change in diet must be done gradually. If your kitty requires a new food for medical reasons, make the switch slowly and add only ten percent of the new food, decreasing the old food by ten percent, over a period of several days.

Bland Diet

If your cat doesn’t seem eager to eat at meal time this can be a big problem. You may need to change what you feed your cat. Cats are picky and stubborn and have their preferences. If you feed your cat a bland diet or cheap pet food, they can refuse to eat for days.

Try to make the food more appealing by including some flavor add-ins, also known as toppers. You can mix in a little fish oil or a spoonful of tuna for extra protein and fat. If that doesn’t seem to work and they only ate the topper, you can purchase gravy that’s specifically designed for cats. You can find this product at most pet stores. Most cats find wet food very appealing, so if you normally feed them kibble, try offering wet food instead.

Add Some Treats

If your cat seems to love their usual pet food, they may simply need some extra calories. Try offering high protein treats or snacks loaded with healthy fat, between meals.


Have you recently moved, changed up the décor in the home, or brought a new pet home? Maybe you just had a baby, or for other reasons, the cat’s home life has changed dramatically. Some cats don’t do well with change. In fact, it can be very stressful for them. In some cases, high levels of stress can be enough to cause your cat to stop eating, or they may eat only a fraction of what they used to. When stressed, some cats will also experience some type of gastrointestinal discomfort and may vomit often or have chronic diarrhea.

If your cat’s weight loss is due to stress, determine what is causing the stress. There’s nothing you can do to remedy the situation if the source of the stress is a new baby or a new home. The cat must learn how to adapt. However, during this time, you can find a quiet spot in the home where the cat can get away from the source of their stress and relax. A bedroom with a cat bed, some food and water, a litter box and some toys may be exactly what your cat needs to start feeling better. If you don’t see any progress in a week or two, speak with your veterinarian on what else you can do to encourage weight gain in stressed and anxious cats.

Multi-Cat Homes

If you have more than one kitty in the home and you have one underweight cat and a couple of overweight cats or dogs, check up on how your cats or dogs interact during mealtime. It’s possible that the other cats or the family dog are bullying the smaller underweight cat and eating his or her share of the food. If this is the case, you need to set up a quiet area for the bullied cat or kitten to eat and drink. Separating the cats may seem like a challenge, and of course you want everyone to get along, but it will be in the best interest of the bullied cat. At some point, once the cat has gained weight, you can try to reintroduce him or her to the other pets in the home. However, if it continues to be an ongoing issue, you will need to keep your cats separated.

Strays or New Cats

As I mentioned earlier, a new environment can be very stressful to cats, especially if that new environment has other animals. Many cats in shelters become so stressed that they will refuse to eat while they are there. Unfortunately, this is very common, so it’s not surprising that the new cat you’ve brought home seems too thin. With strays, there is definitely a shortage of food that’s accessible to them, especially during the winter, when hunting for prey can be challenging in inclement weather. If you’ve recently given a stray a home or adopted a new cat, be patient during this time. They may be reluctant to eat until they feel comfortable and safe in their new home. Offer wet food to encourage weight gain and give them plenty of space and a quiet place to rest as they adjust.

How to Put Weight on a Cat

underweight cat

As a pet parent, you probably get stressed out at the thought they’re not getting what they need.

Fortunately, for some cats, a change in diet can do the trick. Switching to a new food, one that’s more potent and tastier, with a new and exciting texture may be enough to encourage your cat to eat more food. Of course, the nutritional content of that food should also be top notch.

Switch to the Best Cat Food

Typically, the best cat food for underweight cats tends to be higher in calories and fat, made with a limited amount of plant-based ingredients, and made with several different sources of animal ingredients.

Speak with your vet before you try adding new foods.

If your veterinarian agrees that changing your cat’s food is a great idea, then you need to make this change gradually, to avoid digestive upset. Wet food is often more appetizing to pets and it contains a high level of moisture, so wet food is a great choice for cats who don’t drink enough water.

Help Your Cat Gain Weight by Including More Protein

There are many methods you can try, products you can purchase and foods you can offer to encourage your kitty to eat more.

In some cases, the best way to put some weight on is to use food products meant for people to help cat gain weight. These foods include:

  • Tuna
  • Salmon
  • Chicken
  • Eggs
  • Rice
  • Chicken broth

Do not give your cat junk food with their meals. Instead, only lean sources of protein, or some chicken broth if they don’t have much of an appetite. You can also pour the broth over their kibble, to encourage them to eat it.

Monitor Calories

These foods are loaded with nutrients all cats need in meals that will help them thrive. This food should not be seasoned, since some types of flavorings and seasonings can make a cat ill.

Speak with your vet to discuss your cat’s health and determine how many calories he or she needs daily. Measure each of their meals before filling their food bowls.

More Ways to Put Weight On Your Cat

the cat is sick with food

  • Find a high protein cat food. If the weight loss is severe, you may need to temporarily switch to a formula designed for kittens. Kitten food is significantly higher in protein compared to cat food made for adults and can help cat gain weight.
  • If your cat or kitten normally eats kibble, but he or she refuses to eat it, entice your cat with some wet cat food products. You should also make the switch to canned food if your cat is suffering from dental problems, since dry food can be painful for them to eat.
  • Cook for your cat. Whether it’s just heating up their new canned cat food or you’re whipping up some chicken and rice, in some cases, food that’s warmed up will be more appealing to a cat, especially if that cat is older and their sense of smell or taste isn’t what it once was.
  • Do weekly weigh ins to monitor your cat’s weight gain
  • Use lean sources of animal protein for healthy weight gain
  • Count calories in the beginning to ensure your pet is eating enough
  • Add extra animal protein to your cat’s food for proper nourishment


Final Thoughts

The majority of house cats are overweight, not underweight. If you’re certain your cat needs to gain weight, make sure you have him or her examined by their vet before you try any of the tips in this guide. In many cases, if your cat is a senior, an underlying medical condition is to blame. Fortunately, not all medical conditions that cause a lack in appetite or weight loss are serious. Many of these conditions can easily be treated. If your cat has gotten the all clear from their vet, then use this guide to find great food options that your cat is sure to love and tips on what you can do to entice a cat to eat more at mealtime.