Is Your Rat Too Skinny? Here’s How to Tell

Is Your Rat Too Skinny
Is Your Rat Too Skinny

Rats are brilliantly playful pets. They are pretty easy to take care of, especially in the food department. They don’t have very particular likings and will eat most leftovers. But, due to some reasons, rats might lose their appetite and become skinny and unhealthy, without showing major behavioral or physical changes.

Fortunately for us, it’s easy to figure out if a rat is skinny. You can check with your vet once you’ve noticed a loss of weight and change their diet.

So how can you tell if your rat is too skinny? Use this quick guide:

  1. Hold your pet rat in your hand. 
  2. If you feel the bones and find the layer of muscle to be very thin, then your rat is too skinny. 
  3. If you feel the muscle layer more, then the rat has a lean body. A lean body on rats is usually a sign that the rat is active and healthy. 
  4. You can also figure out if your rat is underweight by checking its diet. If they’re eating less, it will make them even skinnier.

If you have a pair of rats and the male weighs less than or equal to the female, then he is definitely underweight.

Of course, once you’ve figured out if your rat is skinny, you need to make some changes in its diet. But there might be some other reasons to them being skinny barring the bad dietary plans. These include aging and illnesses.

Read on to learn how these two cause weight loss, how you can solve these issues, and what a healthy diet of a rat should comprise of.


What is the average weight of a rat?

A male rat should weigh heavier than a female rat. The average weight of a mature female rat is anywhere between 8 to 14 ounces (or 250-400g). The average weight of a mature male rat is anywhere between 14-18 ounces (or 450-520g).

Causes of weight loss in rats


Age is a natural cause of weight loss in rats, especially in females. And although it occurs mostly without the influence of illness, it should be controlled. A rat must not become underweight or skinny at any age.

Older rats have trouble chewing food, which makes them eat less and become skinny. Give these rats mushy foods so they can fulfill their calorie needs. If you give your rats rat blocks or other hard foods, soak it in Fortify or Ensure, preferably chocolate-flavored. You have to soak the food just long enough for it to become mushy. Make sure to clean the cage and throw the mushy food away after a couple of hours. Offer the rats fresh, soft food twice a day.

If your rat has already lost a ton of weight, provide it with easy to chew supplements and include calorie-rich foods in their diet. Check with your vet; they’ll help you pick the right supplements.


Eating habits are altered by illnesses as well. Rats have a pretty fast metabolism, and they process their calories efficiently, which can lead them to lose weight during sickness. Since rats don’t stop eating during the early days of an illness, you should weigh them twice or thrice every week on a small scale and monitor the changes. Get in touch with a vet if your rat is losing weight despite being young and receiving a healthy diet.

Weight loss in rats is a sign of many diseases. Rats who are losing weight and aren’t eating might be suffering from some respiratory issues as they face difficulty breathing. It’s often caused by mycoplasma bacteria, which are known for causing pneumonia. Sneezing, coughing, chattering, gasping, and wheezing will be observed in rats who suffer from respiratory tract illnesses along with weight loss.

Loss of appetite is caused by a variety of bacterial infections. Contact your vet if you observe any symptoms such as coat damage, hunched posture, behavioral changes, staining around nose and eyes, etc. Symptoms of bacterial infections escalate to life-threatening very quickly in rats. 

Weight loss, coupled with tiredness and fluid retention, signals possible heart disease. Weight loss and increased urination & thirst might indicate kidney damage. Weight loss due to the inability to pick up food suggests a stroke or tumor.

A Healthy Diet for Rats

Rats really don’t mind eating anything, so it’s up to the owners to provide them with a healthy diet that provides them with all the necessary nutrients.

The perfect diet should include;

Rat nuggets

These contain the right balance of nutrients for your rat. Rats easily gain weight, so follow the feeding guidelines on the packet and weigh their food out each day to make sure you aren’t giving them too much. You can buy rat nuggets in pet shops.

A small number of fresh vegetables and fruits

Of course, you can’t feed your rats just rat nuggets. Some quantity of fresh vegetables and fruits should be given once per day or two. There’s a long list of rat-friendly, nutrient-packed vegetables, fruits, and herbs that you can give to your rodent and keep it healthy. These include;

  • Fruits like pear, peach, banana, apple, kiwi, melon, strawberries, raspberries, blueberries, plums and avocados. Make sure all the fruits are seedless. Avocados help quickly gain weight, but their pit, leaves, rind, and skin are all toxic.
  • Vegetables like carrot, cabbage, sweet pepper, cress, courgette, chicory, celery, broccoli, cucumber, cauliflower, and peas.
  • Herbs like basil, parsley, coriander, and sage.

Never feed your rats citrus fruits, iceberg lettuce, rhubarb, raisins, uncooked beans, mangoes, pure chocolate, and walnuts. These are unhealthy options and can even be toxic.


If you want the rat to gain some weight and stay healthy, you can give occasional treats like egg, lean meat (such as liver), mealworms, dog biscuits, yogurt, and chickpeas.

Chewable Items

Rats love to chew, gnaw on, and shred things. It’s going to keep their teeth healthy and help relieve pain in rats who are about to grow their set of teeth. It also stops them from getting bored and showing aggressive behavior. You can give rats coconut shells, cardboard, hay cubes, seagrass, pumice stone, and cooked bones to chew.

You can also provide your rat with softwood. But make sure the wood is free from preservatives and chemicals. You can bake the wood for an hour on very low heat and wash it to make it easier to chew. Woods rats love to chew on include dogwood, apple, hazelnut, pear, hawthorn, poplar, grapevine, quince, yucca, and willow.

How to plump up rats

If you don’t provide your skinny rat with proper nutrition, even for a day, then its chances of recovery are jeopardized. As soon as you notice obvious signs of weight loss, get started with diet treatment. Here’s a couple of things you can try;

  • Mix two scoops of lactose-free human baby formula milk (soy preferably) with some warm water. Add liquid vitamin B extract. Feed this to your rat. If it doesn’t eat, feed it by hand using an eyedropper or a syringe (take the needle out before feeding). 
  • Feed highly nutritious and calorie-rich fruits once a day for several days. Try feeding egg yolk (cooked), tuna, salmon, bread, almonds, pistachio, sunflower seeds, baby food, yogurt, banana, and cream cheese.
  • You can also feed your leftovers in a small amount.

If your rat is sick, it needs more fluids than usual to combat the caught illness. Provide the rat with a water bottle containing diluted fruit juice (only apple flavor for males as citrus can lead to kidney problems). Fluid containing foods should be part of a healthy diet.