How to tell if your guinea pig is sick: 10 signs to watch for

• Guinea pigs are prey animals that instinctively mask signs of illness, so problems can go unnoticed until they become serious.
• The ten most important signs include appetite loss, lethargy, weight changes, altered droppings, eye or nasal discharge, breathing changes, skin and coat changes, teeth grinding, unusual hiding, and lumps or swelling.
• Some symptoms require same-day veterinary attention, including not eating for 6-12 hours, labored breathing, seizures, or extreme weakness.

Guinea pigs are not always easy to read when something is wrong. As prey animals, they are instinctively wired to hide signs of illness or weakness, which means by the time a guinea pig looks obviously sick, they may have been unwell for some time.

That doesn't mean you should constantly worry, but it is a good reason to know what to look for. Owners who are familiar with their guinea pig's normal behavior and appearance are far better prepared to notice when something is off.

This guide covers ten of the most important signs that a guinea pig may be sick, what to do at home, and when to contact a vet.

In the wild, showing signs of weakness makes an animal a target. Guinea pigs carry this instinct, which means they often continue to look and behave relatively normally even when they are not well. By the time a guinea pig stops moving around, stops eating, or shows obvious physical changes, the underlying problem is typically not new.

This is one of the reasons routine monitoring and wellness checks matter for guinea pig owners. The more familiar you are with your guinea pig's usual weight, behavior, and appearance, the earlier you are likely to notice a change.

1. Not eating or loss of appetite

A guinea pig that has stopped eating or is eating significantly less than usual needs prompt attention. As discussed in detail in our guide to guinea pig not eating, their digestive system requires a continuous intake of food to function properly. A guinea pig that has not eaten for 12 hours or more, or one who is eating far less than normal, should be assessed by a vet.

Watch for: ignoring food that is normally eaten enthusiastically, leaving hay untouched, or showing interest in food but not eating it (which can indicate dental pain).

2. Lethargy or unusual stillness

Guinea pigs are typically active, curious animals. A guinea pig that is sitting hunched in one spot, barely moving, or showing little interest in their surroundings is showing a significant warning sign. Lethargy is one of the most consistent indicators that a guinea pig is unwell, regardless of the underlying cause.

3. Weight loss

Weight loss can be gradual and easy to miss without regular monitoring. Weighing your guinea pig weekly using a kitchen scale is one of the best things you can do as an owner. A healthy adult guinea pig weighs between 1.5 and 2.6 pounds depending on sex and individual variation. A loss of more than a few percent of body weight over a short period warrants veterinary attention.

Even without a scale, running your hands along your guinea pig's sides and spine can reveal whether they are losing condition. You should be able to feel the ribs slightly but should not feel them prominently.

4. Changes in droppings

Normal guinea pig droppings are firm, oval-shaped, and consistent in size and color. Changes in the droppings are often one of the first signs that something is off with a guinea pig's health.

Diarrhea, meaning watery or unformed stool, is concerning, particularly if it persists or is accompanied by other symptoms. Fewer droppings than usual, very small droppings, or droppings that are unusually misshapen can all point to a digestive problem. For more detail, see our guide to guinea pig diarrhea.

You may also notice soft, clustered droppings that look different from regular fecal pellets. These are cecotropes, a normal part of guinea pig digestion that they typically eat directly. Finding them in the cage can mean your guinea pig isn't consuming them, which may indicate pain, dental problems, or difficulty reaching them. Persistent cecotrope accumulation is worth mentioning to a vet.

5. Eye or nasal discharge

Some degree of moisture around a guinea pig's eye is normal, but persistent discharge, particularly if it is colored, thick, or causing the fur to mat, is not. Yellow or green discharge from the eye typically indicates infection and needs veterinary treatment. For more information, see our guide to guinea pig eye infections.

Nasal discharge is also worth noting. A guinea pig with a runny nose, particularly if the discharge is thick or they are sneezing frequently, may have a respiratory infection.

6. Labored or noisy breathing

Guinea pigs breathe quietly. If you notice your guinea pig wheezing, clicking, crackling, or breathing in a way that sounds effortful, this is a sign of a potential respiratory problem. Respiratory infections are common in guinea pigs and can deteriorate quickly if not treated. Labored breathing in a guinea pig always warrants same-day veterinary attention.

7. Hair loss or skin changes

Patchy hair loss, flaky skin, redness, or crusting on the skin are signs that something is going on that needs investigation. In guinea pigs, these changes most commonly indicate a mite infestation or a fungal infection. Both are treatable, but confirming which one is present matters because the treatments are different. For more information, see our guide to guinea pig mites.

Note that some hair loss around the face is normal in certain situations, such as after dental work, but unexplained patches of hair loss should be assessed.

8. Teeth grinding or drooling

Teeth grinding in guinea pigs is distinct from the happy chattering sound they sometimes make when content. A grinding sound accompanied by other signs of illness, reluctance to eat, or drooling around the mouth is typically a sign of pain. Dental disease is very common in guinea pigs and is a frequent underlying cause. Drooling, wet chin fur, or food dropping out of the mouth while eating are also signs worth taking seriously.

9. Hiding more than usual

Guinea pigs are social animals and usually enjoy interaction with familiar people and environments. A guinea pig that is consistently hiding, avoiding contact, or retreating to a corner of their enclosure when they normally do not can be responding to pain or illness. Combined with any other sign on this list, behavioral withdrawal is a meaningful indicator.

10. Lumps or swelling

Lumps under the skin are not uncommon in guinea pigs and can represent a range of things, from abscesses and cysts to tumors. A lump that appears suddenly, grows quickly, feels warm, or seems to cause discomfort should be assessed by a vet promptly. Not every lump is an emergency, but none should be ignored without professional guidance.

Establishing a simple weekly routine helps you stay familiar with your guinea pig's baseline and catch changes early. This does not need to be elaborate.

Weigh them. A consistent weight is a reassuring sign. Any drop of more than a small amount over a week is worth noting and discussing with a vet if it continues.

Check their eyes and nose. Both should be clear of significant discharge. A little moisture in the corner of the eye can be normal, but watch for any changes in color or volume.

Look at their coat and skin. Run your hands gently along their body, checking for patches of hair loss, dry or flaky skin, lumps, or any areas that seem sensitive to touch.

Observe their droppings. Check the litter tray or cage floor for signs that droppings have changed in volume, consistency, or color.

Watch them eat. Note whether they approach food with their usual enthusiasm and eat without apparent difficulty.

These checks take only a few minutes and give you a reliable picture of what normal looks like for your individual guinea pig.

Some symptoms are more urgent than others. Contact a vet the same day if your guinea pig:

• Has not eaten for 6-12 hours or more
• Is breathing with obvious effort or making sounds when breathing
• Has had a seizure or a seizure-like episode
• Has a bloated or noticeably firm abdomen
• Is not moving around and seems very weak
• Has rapid or significant weight loss

For symptoms that are less acute but still concerning, such as mild eye discharge, minor changes in stool, or behavioral changes, scheduling a prompt appointment rather than waiting for the next available routine slot is always the right call.

Talk to a Vetster vet about your guinea pig's health

Yes. Vetster vets see guinea pigs and other exotic pets, not just dogs and cats. Online appointments are available 24 hours a day, seven days a week, which is particularly useful when you notice something concerning in the evening or on a weekend.

An online vet appointment is well suited to situations where you want a professional opinion on whether what you are seeing is normal, need guidance on what to monitor and for how long, or want to triage symptoms before deciding whether an in-person visit is needed.

Some situations, such as a guinea pig that needs an exam, diagnostics, or hands-on treatment, will require an in-person visit. A Vetster vet can help you determine which situation you are in.

Book an online vet appointment with Vetster

Knowing your guinea pig's normal behavior, weight, and appearance is one of the most valuable things you can do as an owner. The earlier a health problem is spotted, the more options there are for treatment and the better the outcome tends to be.

Trust your instincts. If something feels off with your guinea pig, even if you cannot quite identify what it is, that is worth acting on. A quick conversation with a vet is always better than waiting and watching when it comes to small animals.