Home » Why Is My Hamster Getting Thinner?
why is my hamster losing weight?

Why Is My Hamster Getting Thinner?

Last Updated on: 24th September 2023, 04:00 pm

It’s common for a hamster’s weight to fluctuate, but sudden or rapid weight loss is a problem.

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

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

Is My Hamster Underweight?

The easiest way to tell if your hamster’s a healthy weight is to weigh them on the kitchen scales. Hamsters change size quickly, so weighing them weekly allows you to check if they’re getting skinny.

You can also determine if your hamster is underweight by checking how it looks and feels. Hamsters shouldn’t be noticeably bony, so the next time you hold your hamster, stroke its back, shoulders, and ribs.

If you can feel bones instead of a soft cushion of flesh, your hamster is underweight.

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

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

Due to the way they’re bred, pet store hamsters are smaller, while ethically bred hamsters are larger. Female hamsters also tend to be bigger than male hamsters.

Why Is My Hamster Losing Weight?

It’s concerning to see a once-healthy hamster become thin. While weight loss doesn’t always mean your hamster has a health issue, it signifies that something’s not right.

If your hamster looks skinny or loses weight fast, it could be for the following reasons.


As hamsters are so small, it’s easy to underestimate how much food they need and how often you should feed them. To stay healthy, hamsters eat 11-14 grams of food each day.

Syrian hamsters need two teaspoons of pelleted food every 24 hours, while dwarf hamsters are okay with one tablespoon.

Offer small quantities of food daily, but be careful, as your hamster will store most of it in its cheeks.

Nutritional Deficiencies

You may be feeding your hamster enough food, but is the quality sufficient? 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 the nutrients pass through the body without being absorbed. Unfortunately, this causes malnutrition and 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:

  • Cooked meat, like chicken.
  • Cooked fish or seafood.
  • Crickets.
  • Grasshoppers.
  • Mealworms.
  • Boiled eggs.

Teeth Issues

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

As described by Cell Reports, hamsters’ teeth never stop growing because the root canal constantly grows new tooth tissue. So, they have open-rooted teeth that continue to get longer quickly.

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.

Overgrown teeth have the following characteristics:

  • Don’t meet in the middle.
  • Appear misaligned.
  • Become curved or stick out.
  • Get stuck on things.

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

Also, some hamsters break a tooth by chewing on something hard, like their cage bars.

what to do if your hamster is losing weight

Impacted Cheek Pouches

Cheek pouches become impacted when bits of food get stuck. This leaves the hamster unable to empty its pouch without assistance from an owner or veterinarian.

Cheek pouches don’t have salivary glands, so sticky foods such as wet pasta and dry nesting materials get stuck, blocking the pouches and causing painful infections and abscesses.

Because hamsters struggle to eat, they lose weight. Common signs of cheek impaction include:

  • Pouches appear full.
  • The neck and head feel swollen.
  • Excessive saliva production.

To help your hamster start eating again, you’ll need to empty the cheek pouches by doing the following:

  1. Massage the cheek pouches to dislodge any stuck food.
  2. Fill a syringe with lukewarm water and squeeze it into the mouth to flush the pouch.

If that doesn’t work, 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 (proliferative ileitis) is a serious condition that commonly affects Syrian hamsters aged 3-6 months and elderly hamsters who are too frail to clean themselves.

It’s caused by an overgrowth of bacteria, which is due to the following:

  • 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 food.

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


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

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 avoid being eaten by predators. Sometimes, the only sign that your hamster’s sick is weight loss due to loss of appetite.

While some conditions clear up, hamsters can experience serious ailments.

Kidney Inflammation

MSD Veterinary Manual stated that kidney inflammation (nephritis) is common in older female hamsters, causing them to lose weight, drink excessive water, and produce more urine than usual.

Kidney inflammation is commonly caused by the following:

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

The condition worsens, but antibiotics, vitamin B complex, and fluids are beneficial.

Increased Exercise

Wild hamsters run up to 6 miles a night and spend time foraging for food and evading predators. In captivity, hamsters run on their wheels to burn off energy and stay 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 due to the increased activity.

Hamsters also run more when bored or stressed, so keep their environment safe and comfortable.

Stressed Out

Hamsters are prey animals, so they lose weight through stress. Stress triggers include:

  • Loud noises.
  • Bright white light.
  • They are 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, most hamsters are highly territorial and will fight each other to the death.

If you’re housing several 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?

Hamsters can become thin even while they’re still eating. It’s possible that your hamster can’t absorb nutrients from its food due to the following:

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

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

In the winter, when it’s cold, hamsters stash their food and tuck themselves into their warm burrows, coming out only for a few hours for a drink and to run 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 it’s not in pain in 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 its favorite foods and 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:

Additional Protein

Assess how much protein a food mix provides, especially if a hamster is fed an all-seed diet. If it’s less than 16%, switch to a more nutritionally dense food mix.

Most lab blocks are scientifically formulated to give a hamster the necessary nutrients. However, providing amino acids through chicken, fish, insects, and hard-boiled eggs is also important.

Remove any uneaten protein to prevent the food from decomposing.

Clean The Enclosure

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

Remove any 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 harmful bacteria.

If the hamster has already fallen sick, completely replace its bedding. You shouldn’t do this often, as removing a hamster’s scent is a stressful experience.

While weight loss isn’t always abnormal, you should identify the cause. If you notice the hamster is thinner than usual, you should get it checked by a veterinarian.