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why is my hamster losing weight?

Why Is My Hamster Getting Thinner?

(Last Updated On: May 28, 2022)

It’s common for a hamster’s weight to fluctuate. However, sudden or rapid weight loss signifies a problem that needs to be addressed.

Hamsters become thin due to under-feeding and nutritional deficiencies. Illnesses, such as wet tail and kidney inflammation, can be to blame.

If your hamster’s teeth become too long, they’ll prevent them from eating. Also, hamsters can lose weight because they’re exercising more than usual.

Hamsters come in all shapes and sizes, making it difficult to tell when they’re losing weight. If you’ve noticed your hamster has lost weight, get it checked over by a veterinarian.

Is My Hamster Underweight?

The easiest way to determine whether your hamster’s a healthy weight is to weigh it on the kitchen scales. Hamsters change size quickly, so weighing them once a week enables you to check if they’re suddenly getting skinny.

You can also determine whether your hamster’s underweight by paying attention to how it looks and feels. Hamsters shouldn’t be noticeably bony. The next time you hold your hamster, gently stroke its back, shoulders, and ribs. If you can feel bones instead of a soft cushion of flesh, your hamster’s underweight.

While all hamsters are different depending on their genetics, how much food they eat, and the quality of their nutrition, these are the average healthy weights for each species:

Hamster BreedAverage Healthy Weight
Syrian120-200 grams
Roborovski25-30 grams
Chinese30-45 grams
Winter White30-45 grams
Campbell’s30-45 grams

Because of the way they’re bred, pet store hamsters tend to be smaller, while pedigree, ethically-bred hamsters are larger. Female hamsters also tend to be significantly larger than males.

Why Is My Hamster Losing Weight?

It’s concerning to see a once-healthy hamster become thin. While weight loss isn’t always the sign of a health issue, it signifies that something’s not quite right.

If your hamster is looking too skinny or losing weight fast, it could be for the following reasons.


Because hamsters are so small, it’s easy to underestimate how much food they need and how often you should feed them. Hamsters eat 11-14 grams of food (pellets, seeds, fruits, and vegetables) per day to stay healthy.

Syrian hamsters need approximately 2 teaspoons of pelleted food every 24 hours, while dwarf hamsters are fine with one tablespoon. Incorporate small amounts of seeds and fresh foods every day, but be careful as your hamster will store most of it in their cheeks.

Nutritional Deficiencies

You may be feeding your hamster enough food, but is the quality good enough? Not all hamster foods are created equal, and the low-quality brands (like Oxbow) bulk out their mixes with hay.

Hamsters don’t get nutrition from hay, which means that the nutrients in these foods pass through the body without being absorbed. This causes malnutrition and extreme weight loss, starving hamsters to death.

Hamsters also need around 16% of their diet to consist of protein. As omnivores, the following foods are a healthy way to provide them with the protein they need:

Teeth Issues

Dental issues are one of the most common reasons for weight loss.

As described by Cell Reports, hamsters’ teeth never stop growing. That’s because the root canal constantly grows new teeth tissue, which means they have open-rooted teeth that continue to get longer in a short space of time.

If hamsters don’t have wooden toys or tough foods to chew on, their teeth grow too quickly, making it difficult for them to eat. In extreme cases, extra-long teeth cause the mouth to fuse shut, preventing hamsters from eating. This results in rapid weight loss.

Overgrown teeth:

  • Don’t meet in the middle
  • Appear misaligned
  • Become curved or stick out
  • Get stuck on things, such as cage bars

Your hamster will struggle to eat and may chew on its chew bars to try to wear its teeth down. These are signs that you need to have your hamster’s teeth professionally trimmed by a vet.

what to do if your hamster is losing weight

Impacted Cheek Pouches

This is where bits of food get stuck, leaving the hamster unable to empty them without help.

Cheek pouches don’t have salivary glands, so sticky foods such as wet pasta and dry nesting materials get stuck, block the pouches, and cause painful infections and abscesses. Because hamsters struggle to eat, they lose weight.

Common signs of cheek impaction include:

  • Pouches appear full
  • Neck and head feels swollen
  • Excessive saliva production
  • Rapid weight loss

To help your hamster start eating again, you’ll need to help empty the cheek pouches.

You can do this with these steps:

  1. Gently massage the cheek pouches to dislodge any stuck food
  2. Fill a syringe with lukewarm water and squeeze it slowly into your hamster’s mouth to flush the pouches out
  3. Take your hamster to the vet to have the food removed

Mouth or Airway Obstructions

Mouth and airway obstructions are similar to cheek impaction in that they cause hamsters to become thinner, but they can be more serious.

Large nuts and inedible toys they’ve attempted to pouch can become stuck, leaving hamsters unable to eat. You’ll need to act fast to prevent your hamster from suffocating or choking on the obstruction.

Wet Tail

Wet tail is a serious condition that most commonly affects Syrian hamsters aged between 3-6 months and elderly hamsters who are too frail and weak to clean themselves.

It’s caused by an overgrowth of bacteria due to:

  • Unsanitary conditions
  • GI tract inflammations
  • Stress
  • Overcrowding
  • Nutritional deficiencies
  • Transportation
  • Diseases requiring antibiotics

Wet tail causes repetitive diarrhea, preventing the body from receiving nutrients from anything the hamster eats.

If hamsters don’t receive immediate veterinary treatment, which usually involves a week-long course of antibiotics, they’ll starve, losing a large amount of weight. Sadly, wet tail is fatal in approximately 90% of cases.


Constipation causes hamsters to lose their appetite, which, in turn, results in weight loss. They also appear lethargic.

Constipation is most commonly caused by:

  • Intestinal parasites, such as tapeworms
  • Blockages caused by bedding or fibrous materials
  • Intussusception, which is where a portion of the intestines folds into itself

This condition can be serious, so get your hamster checked by a vet if it appears suddenly thinner and refuses to eat.

General Sickness

Weight loss is a common by-product of sickness, and it’s common for hamsters to feel under the weather.

Since hamsters are prey animals, they hide their sickness to prevent themselves from being eaten by predators. Sometimes, the only sign that your hamster’s sick is because of weight loss from where it’s lost its appetite.

While some conditions clear up on their own, hamsters experience a range of serious ailments.

Kidney Inflammation

According to MSD Veterinary Manual, kidney inflammation, otherwise known as nephritis, is common in older female hamsters. It causes hamsters to lose weight, drink excessive water, and produce more urine than usual.

Kidney inflammation is commonly caused by:

  • A viral infection
  • High blood pressure in the kidneys
  • Immune system disorders

The condition gets worse over time, but there are various treatments available, such as a course of antibiotics, a vitamin B complex, or fluids.

Increased Exercise

Hamsters lose weight naturally through exercise. They can run up to 6 miles a night in the wild and spend a significant amount of time foraging for food and evading predators. In captivity, hamsters enjoy running on their wheels to burn off energy and keep themselves mentally stimulated.

If you’ve recently provided your hamster with a running wheel or increased its size, you may find it runs more than it used to. In this case, your hamster appears thin from increased exercise.

Hamsters also run more when they’re bored or stressed. Make sure your hamster’s environment is safe and comfortable, and keep monitoring its weight to ensure it doesn’t drop to an unhealthy level.


Because hamsters are prey animals, they lose weight through stress.

Hamsters have many stress triggers, such as:

  • Loud noises
  • Bright white light
  • Being disturbed during the day while they’re sleeping
  • Predatory pets
  • Unsanitary conditions
  • Small cages
  • No access to an exercise wheel or enrichment
  • Bullying from dominant littermates

Similarly, hamsters are solitary animals. They’re highly territorial and will fight each other to the death.

If you’re housing multiple hamsters in the same cage, you must separate them. It’s not uncommon for one hamster to become dominant, claiming all the food and leaving nothing for the submissive hamster.

Why Is My Hamster Eating But Losing Weight?

Weight loss doesn’t always go hand in hand with decreased appetite. Hamsters can become thin even while they’re still eating. It’s possible that your hamster cannot absorb the nutrients from its food.

This could be due to:

  • Low-quality diet
  • Sickness and disease
  • Bacterial infections
  • Parasites
  • Digestive tract issues

It’s also natural for weight to fluctuate. Hamsters go through increased activity levels from time to time, particularly when it’s the right temperature.

In the winter, when it’s cold, hamsters tend to stash their food and tuck themselves into their warm burrows, coming out only for a few hours for a drink of water and a quick spin on their exercise wheel.

This is normal, but ensure your hamster’s cage isn’t too hot or cold. 65°F to 75°F is optimal.

is my hamster underweight?

Do Hamsters Lose Weight Before They Die?

Hamsters slow down significantly before they die. They show little interest in drinking or eating and rarely have the energy to consume large amounts of food.

An old hamster losing weight is normal, but you must ensure that your pet’s not in any pain or discomfort during the final stages of its life.

Your hamster likely only has a few days left to live, so minimize its weight loss and increase its energy levels by offering it some treats.

However, if your hamster has a health condition contributing to its weight loss, you’ll need to consider euthanasia to ease its discomfort. Follow this advice on how to care for a dying hamster.

How To Fatten Up a Skinny Hamster

It’s important to know what to do if your hamster is losing weight to prevent it from becoming too thin.

Follow these steps to keep your hamster healthy:

Provide Additional Protein

We’ve mentioned how nutritional deficiencies and a lack of protein are responsible for thinness.

Look at how much protein your food mix provides, especially if your hamster’s on an all-seed diet. If it’s lower than 16%, you’ll need to switch to a more nutritionally dense food mix.

Most lab blocks are scientifically formulated to provide your hamster with all the protein, vitamins, and minerals it needs. However, it’s also important to provide amino acids through chicken, fish, insects, and hard-boiled eggs.

Remove any uneaten protein to prevent the food from decomposing and making your hamster sick. You’ll also want to remove it from your hamster’s enclosure before it hides it in its burrows.

Clean Your Hamster’s Enclosure

Keep on top of cleaning your hamster’s cage. Unsanitary conditions attract harmful bacteria, causing sickness and subsequent weight loss.

Remove all soiled bedding and sand and replace it with clean substrate. You’ll also need to remove any soiled food in case it’s been tainted with bacteria.

If your hamster has already fallen sick, completely replace its bedding. This isn’t something you should do very often, as removing your hamster’s scent is a stressful experience.

While weight loss isn’t always abnormal, you should always investigate the cause. If you notice that your hamster is thinner than usual, you should get them checked over by a veterinarian.