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Why Is My Guinea Pig Losing Weight? (Causes & Diet Plan)

Tim Rhodes
Written by Tim Rhodes Last Updated: November 20, 2021

A guinea pig losing weight might suffer from serious health problems.

However, don’t panic, guinea pig’s weight fluctuates throughout the year, although not significantly.

So, when a guinea pig is obviously losing weight, and especially if it happens rapidly, guinea pig owners have a good reason for concern.

How Much Do Guinea Pigs Weigh?

When born, guinea pigs only weigh around 100g, they will get full weight within the above eight months.

The adult male’s average weight is between two to three pounds, and the female weighs 1.5 to 2.5 pounds.

Anything above 100 grams is a trigger of alarm.

Usually, guinea pigs live between five to seven years.

Apart from changes in your guinea pig’s diet, guinea pigs lose weight as they get older.

Good nutrition is essential for them to assisting fighting against illnesses and maintaining their appetite.

What Causes Weight Loss in Guinea Pigs?

Many underlying diseases can cause weight loss in guinea pigs.

Poor health is one of the worse and more threatening problems in guinea pigs losing weight.

If guinea pigs lose bodyweight more than 5% than, you should take them to the vet.

Below we present some of the significant causes of weight loss in guinea pigs.

Teeth Problems

Malocclusion causes pain and discomfort, which makes a guinea pig unable to eat, and thus lose weight.

Overbite or underbite creates a challenge for a guinea pig.

Chewing becomes difficult and extremely painful.

Eventually, if untreated, a guinea pig may starve to death.


Poor appetite for any reason leads to significant weight loss.

As soon as you notice your guinea pig losing weight, take it to the vet immediately.


Vitamin C deficiency causes many problems, including hair loss, lethargy, and weight loss in guinea pigs.

Improper Diet or Poor Quality Hay

Due to off-balanced nutrients, guinea pigs may lose weight.

Make sure that the hay you are giving to your guinea pig is of excellent quality.

Extreme Temperatures

Guinea pigs may react badly to changes in temperature, so make sure that the room in which they live is always well ventilated, neither hot nor cold.

Lack of Water

Dehydration causes weight loss in all living organisms, including guinea pigs.

It’s essential to keep your guinea pig hydrated throughout the day.

Make sure that your pet always has fresh and clean water in its water bowl or water bottle.

Change the water frequently.


Viruses and bacterial infections cause guinea pigs to lose weight in a short period and in an unhealthy way.

Consult a vet as soon as possible, so your guinea pig can receive the right treatment.

Dominant Guinea Pigs Eat All the Food

In some cases, dominant guinea pigs get all the food, without leaving anything for others.

Inferior guinea pigs become malnourished, which is a cause of concern.

Malnourishment creates health problems and weight loss is an obvious symptom that something is wrong.

Malnourishment From An Early Age

Due to robust growth, the guinea pig never reached its potential body weight.

Gastrointestinal Diseases and Other Health Problems

Gastrointestinal diseases are painful and dangerous.

A guinea pig suffering from gastrointestinal problems might be in pain, stop eating, become malnourished, and lose weight rapidly.

If left untreated, the consequences might be fatal.

Changes in the Environment

Guinea pigs lose weight if you change their home or bring a new guinea pig to share the crate.

Yes, it is a good idea to have more than one guinea pig, as these small animals are social beings and need a friend of their own kind.

Yet, the introduction between the two shouldn’t be sudden.

Also, changes in the lighting and the room’s climate can significantly impact a guinea pig’s health.

Some other significant reasons for rapid weight loss in guinea pigs are respiratory and metabolic issues as well as urinary tract infections.

What Are the Signs of Weight Loss in Guinea Pigs?

You need to look out for other signs as well if your guinea pig is losing weight.

If a guinea pig is losing weight and drinking a lot of water more than usual, it’s a sign of diabetes.

Diabetes is a common disease in guinea pigs, and weight loss is a common sign of the same.

Other symptoms are frequent urination, rapid cataract formation, and frequent urinary tract infection.

If the above symptoms are found, it is suffering from diabetes, which causes it to lose weight frequently.

Sometimes pigs have some parasites and worms in their guts, which often suck their nutrients out of the food that guinea pigs consume, which results in weakening the digestive system of pigs.

Weight loss is directly proportional to the loss of appetite.

If your guinea pigs are not eating the food properly, they will ultimately lose weight.

How to Make a Guinea Pig Gain Weight?

The diet plan and food for weight gain are given below.

Keeping the record of the weight in the notebook to monitor the fluctuations of the weight.

Weigh weekly and have a schedule; this could be a specific day in the week.

In general, guinea pig’s weight is cited as 900 = 1200 grams for males and 700 – 900 grams for females.

However, there may be variations in the weight depending upon the individual, this is why you should monitor and weigh the pets frequently when they are healthy.


Alfalfa hay is great for every nursing female guinea pig.

Pregnant and malnourished guinea pigs can also benefit from alfalfa.

However, its high calcium content makes it unsafe for adult guinea pigs, as calcium is responsible for the creation of bladder and kidney stones.

 Still, if you are trying to help an underweight guinea pig restore a healthy weight, limited amounts of alfalfa can help.


Guinea pigs, whether healthy or sick, should have unlimited access to hay.

Hay increases digestion and keeps their teeth at the proper length.

Orchard grass, botanical hay, meadow bay, and timothy hay are the most common varieties of hay guinea pigs eat.

Oat Hay

Oat hay contains high fiber and is low in calcium, which is exactly what guinea pigs need.

Read Grass

Read grass is high in protein and fiber, which is a good combination for underweight guinea pigs.

Do Guinea Pigs Lose Weight In Summer Or Winter?

In winter, pigs grow some extra fur to stay warm if the temperature drops down, so its looks were more significant in winter than in summer.

A guinea pig’s appearance has nothing to do with the weight, the fur increases or decreases in weight by a few grams only because of seasonal changes.

What Do Guinea Pigs Need to Be Healthy?

Fresh, clean water continuously twice a day, and ensure the water doesn’t freeze in the winter, without which guinea pigs will be seriously ill.

Their digestive system requires an unlimited supply of good quality hay in their hay feeders and needs grass, which must constitute their diet plan to function correctly.

They graze, eat only herbs and some plants both day and night, making possible fresh grass and vegetables available to them, and their teeth continuously grow; otherwise its wears down.

Incorrect Diet Leads to Dental Problems and Digestion Issues

Washed leafy green provides to them daily as some of the plants are poisonous to them.

Feed them root vegetables, including fruits and carrots, in small amounts as treatment.

Your guinea pigs’ diet must be high in fiber, and if it can’t grazing the grass outside, then they should be supplied unlimited hay to maintain their diet.

They should be feed formulated concentrate food as well because hay doesn’t contain all types of nutrients.

Guinea pigs should be offered complimentary feed and also careful in overfeeding them as it causes dental problems.

Some guinea pig owners don’t weigh their pig weight regularly, and it can be tough to decide that it’s losing weight.

If you haven’t weighted your guinea pigs in the past few days or weeks, you can look into the sign to determine the guinea pig’s underweight.

The skin and coat feel rough and puffed up; the pelvis, ribs, or spine can be felt.

If you notice the above symptoms, it indicates something wrong with your guinea pig’s health, so you should take immediate medical advice.

Apart from these, if there is an unbalanced diet, it leads to weight loss in guinea pigs.

If guinea pigs eat less hay and more vegetables, they need enough calories and fiber to maintain their body weight.

It is essential to make changes in their diet and consult a vet if they are losing weight.

Never Feed Guinea Pigs With High-Calorie Food 

If you put too many calories, it worsens their digestive system gets unbalanced, which results in weight loss for guinea pigs.

Diseases Are Reasons For Weight Loss

The most common of these are scurvy or malocclusion as diagnosed by the veterinarian.

Sometimes, pig’s teeth hurt while eating, and discouraging them from eating causes them to lose weight.

Guinea pigs having diarrhea usually have runny stools and messy rear ends.

Constipation can result from several factors, including a low diet and illness, so veterinary attention is required.

Guinea pigs need vitamin C in their diet, and you should give them mustard greens, dark green leafy vegetables, and turnip greens.

How Can I Keep My Guinea Pig Healthy?

A healthy and balanced diet can prevent many guinea pig health issues.

Pay close attention to your guinea pig’s diet and make sure it’s well-balanced.

Guinea pigs chew on bark and twigs; however, they don’t need these to keep the front teeth worn down.

They need unlimited supplies of hay and grass to keep their teeth trimmed.

Many guinea pig owners offer those chews and wooden logs at home, but it’s not essential.

Yet, if you’d like to give them such a treat, you should know that apple tree and pear tree branches are perfectly safe for guinea pigs.

The best-balanced diet for guinea pigs is 80% hay, and the rest should consist of a mix of fresh vegetables, fruits, and pellets.

If your guinea pig is underweight, you should focus on feeding branded hay with good quality and a cup of fresh vegetables and some extra pellets and 3rd cutting timothy.

How Can I Maintain My Guinea Pig’s Health?

There are many ways to keep your guinea pig away from the diseases which cause their weight loss.

A healthy guinea pig has bright and alert eyes, no sign of cloudiness or redness, and should have clean noses and ears.

Add fresh fruits like apple, banana, kiwi, and other occasional treatments in their diet plan.

You can also add some oatmeal to their diet; it helps in gaining weight and healthy.

You should always keep in mind that introducing new food too quickly or making frequent changes in their diet plan causes the guinea pigs’ sensitive digestive system and lead to health issues in the guinea pigs.

Offer them lettuce, tomatoes, and bell peppers so that it will be best if you feed 1/6th cup of pellets to guinea pigs daily.

Make sure that you serve them good quality pellets having vitamin c and fortified pellets.

Avoid feeding high-level sugar food more than once-twice a week, which leads to a health issue and also causes diabetes and cancer in the guinea pigs.

If you notice a significant change in your guinea pigs’ weight, check whether your guinea pig eats and drinks regularly.

Most of the time insufficient and malfunctioning nutrient causes weight loss in the guinea pigs.

If you found that your guinea pig won’t eat properly, you can quickly change their diet before losing weight.

Different guinea pig food brands in the market spice up with different menus having other vegetables and fruits.

If there is a problem that still exists, then you need to see a vet.

If your guinea pig is not taking food properly, you should start force-feeding him or her.

During force-feeding, you should be careful with the help of a clean syringe.

Sometimes, you notice that your guinea pig loses weight within a safe range, but their week keeps dropping in week after week consistently then you should be more careful about their diet and health.

Excess of vitamin C can cause abnormalities in guinea pigs.

Kidney diseases in the guinea pigs occur mostly in the older guinea pigs, which is a clinical sign including dehydration, depression and weight loss, and also urination and unexpected health.

Weight loss is a sign of the lack of nutrients and illness and causes weight gain due to overfeeding vegetables and pellets.

Conditions You Should Consider

These are the following conditions: severe and need proper veterinary immediately on an emergency basis for your guinea pigs.

  1. Bleeding from the mouth and rectum
  2. Inability to urinate
  3. Not eating for more than 12 hours
  4. Inability or reluctance to move
  5. Extreme lethargy

To keep your guinea pig’s condition good, you will need to handle the diet according to the diet plan and check over for signs of any illness and injuries.

It would be essential for you to make necessary changes to the guinea pigs’ diet plan and consult a vet.

Some good choices of the high-calorie food that can be fed to your guinea pigs are carrots, grapes, watermelons, pears, peas, and lettuces.

Final Thoughts

Poor appetite and urinary tract infections are among the most common reasons for a guinea pig’s weight loss.

Also, vitamin C deficiency causes scurvy, hair loss, and weight loss.

Pain and discomfort due to malocclusion as well as poor health as a result of gastrointestinal problems are significant causes of weight loss in guinea pigs.

To address weight loss in guinea pigs, consult a vet and follow a strict diet plan that will help your guinea pig overcome the problem.


Tim Rhodes
Tim Rhodes

Hi there! My name is Tim Rhodes and I'm a guinea pig enthusiast through thick and thin. My mission is to teach others useful tips and tricks about these cute creatures. When I'm not writing, I enjoy kickboxing and work as an animal trainer.

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