Care guide · Mice

Pet mouse health: signs of illness to watch for

Checked against RSPCA: Mice health and welfare, RSPCA Australia: What does an unhealthy mouse look like?, RSPCA Australia: How should I care for my mice? and 8 more on

A sick mouse often sits hunched with ruffled or dull fur, eats or drinks less, hides more, loses weight, or breathes with clicks, chattering or effort. Mice hide illness until it is serious, so any of these signs, or a new lump, means ringing a vet who sees mice the same day. A weekly hands-on check catches most problems early.

How do you tell if a mouse is sick?

You tell a mouse is sick by noticing a change from its normal look and behaviour, because mice show very little until they are quite ill. The RSPCA warns that mice can go downhill quickly and show only subtle signs of pain until it is severe. Learn what normal looks like for each mouse, and act on small changes.

PetMD describes a healthy mouse as having clear eyes, a clean nose and ears, a shiny coat, clean feet, and teeth and nails that are not overgrown. Yellow-orange front teeth are normal, especially with age.

Signs that mean a vet visit

The RSPCA lists these as reasons to see a vet straight away:

  • Not eating or drinking, or drinking much more than usual
  • Hiding more than usual, or sitting hunched up
  • Ruffled, spiky or dull fur, or a dirty, stained coat
  • Sunken or dull eyes, or discharge from eyes or nose
  • Losing weight, or gaining it quickly
  • Diarrhoea, or passing much more or no urine
  • Chattering or clicking breaths, or slow, fast or uneven breathing
  • Very dark red or very pale ears, nose or feet, or very hot or cold feet
  • Head tilt, fits, twitching, trembling or shivering
  • Grating teeth, wobbling, or not using a leg
  • Gnawing at itself, a hot swollen belly, any injury or a new lump

RSPCA Australia adds the mouse "grimace": a hunched, arched back, ears pinned flat and eyes squinted. It also flags a mouse sitting alone in a corner instead of nesting with the group, and sudden squealing when touched. Our guide to pet mouse behaviour explains which sounds and habits are normal.

How fast should a sick mouse see a vet?

Same day for almost everything, and straight away for an emergency. Because the RSPCA says a mouse can die after losing 20% of its body weight, a mouse that stops eating for even a day is at real risk.

What you see How fast
Laboured breathing, collapse, fits, heavy bleeding, cold and still, suspected poisoning Emergency: ring a vet now, including out of hours
Not eating or drinking, clicking breaths, hunched and ruffled, diarrhoea, head tilt, a wound Same day
Scratching, scabs, bald patches, a small new lump, overgrown teeth, slow weight loss Within a day or two
Mild sneezing once or twice with no other signs Watch closely for 24 hours; vet if it repeats

Not every practice treats mice, so find one before you need it. Woodgreen suggests choosing a mouse-savvy vet, and RSPCA Australia suggests a check soon after you get new mice and at least once a year after that.

Common mouse health problems

The problems vets see most in pet mice are breathing infections, skin parasites, lumps, teeth trouble and wounds from fighting. PetMD's list of common illnesses also includes obesity, heat stroke, diarrhoea and bumblefoot (sore feet).

Problem Signs What vets commonly do
Breathing infection, often mycoplasma Sneezing, sniffling, chattering, laboured breathing, weight loss Antibiotics to control signs; the MSD manual says mycoplasma has no cure, so flare-ups can return
Fur mites Itching, scabs on neck, shoulders and face, hair loss, white specks on hairs Prescribe mite treatment; you clean the whole cage so eggs do not reinfect
Barbering Neat bald patches or missing whiskers on cage mates Rule out mites; the MSD manual says it often needs no treatment unless skin is sore
Lumps and tumours A swelling under the skin, often on the chest, belly or sides Examine and often remove; early surgery gives the best result, says the MSD manual
Abscess A soft swelling, often after a bite Drain, clean and give antibiotics
Overgrown teeth Drooling, dropping food, weight loss, a swollen face Trim the teeth, sometimes regularly for life
Diarrhoea Wet, messy bottom, hunching, dehydration Fluids, medicines for the cause, and a full cage clean
Fight wounds Scabs or wounds on the tail, back and rump, mostly in males Clean, drain and treat infection; separate mice that keep fighting
Ringtail Tight rings round the tail, sometimes the feet Often surgery; caused by dry air, heat and draughts

Only give medicines a vet has prescribed for your mouse. The RSPCA warns that medicines for people and other animals are dangerous to mice, and RSPCA Australia notes some painkillers can kill them. Flea and mite products for dogs and cats are never safe to guess with.

Breathing problems in mice

Breathing infections are among the most common illnesses in pet mice. The MSD Veterinary Manual names mycoplasma as a frequent cause, spread through the air, by contact and from mother to babies. Signs are sneezing, sniffling, chattering, laboured breathing and weight loss, and it can turn into pneumonia. Woodgreen says stress, poor airflow, dusty bedding, temperature changes, bullying and old age all make it worse.

  • Use dust-free, unscented paper bedding, never sawdust or pine or cedar shavings. See our mouse bedding guide.
  • Keep the cage well aired; the PDSA prefers barred cages over glass or plastic.
  • Clean often so ammonia from urine does not build up.
  • Keep the room steady at 18 to 22°C (64 to 72°F), as the PDSA advises, away from draughts. Our pet mouse temperature guide covers hot and cold spells.

Skin problems, mites and hair loss

Scratching, scabs and bald patches are usually mites, but can also be barbering, boredom or an allergy. Woodgreen lists the signs of fur mites as hair loss, red skin, heavy dandruff, ear scratching and scratches round the neck that become open sores. The MSD manual says mites build up when a mouse is stressed or cannot groom properly, and that mouse mites do not infect people.

A vet can confirm mites and prescribe a treatment sized for a mouse. Treat every mouse in the group, and deep clean the cage, as our mouse cage cleaning routine explains. The Crittery notes that boredom can cause scratching too, and some mice react to certain beddings, so if mites are ruled out, add enrichment or change bedding.

Lumps, tumours and older mice

Lumps are very common, especially mammary (breast) tumours in females, say the PDSA and the MSD manual. The MSD manual says they can appear almost anywhere under the skin, not just on the belly. It also says early removal gives the best outcome, though these tumours often spread and the outlook is often poor. The PDSA warns surgery on such a small animal carries risk and tumours often come back.

The Crittery notes that not every lump is cancer: abscesses from bites are often softer, and a mouse with a slow lump can live comfortably for months. A vet can help you decide what is kindest.

Older mice can also get arthritis, heart disease, cataracts and failing sight, says the MSD manual. Blind mice adapt well using smell and touch if you keep the layout the same. Mice usually live 1.5 to 2.5 years, and our guide to how long pet mice live covers gentle care in old age.

How to do a weekly health check

Once a week, handle each mouse and look it over from nose to tail. Woodgreen advises a weekly check, and RSPCA Australia suggests running your fingers gently over each mouse to feel for lumps.

  1. Watch first. Before you open the cage, spend a few minutes watching. RSPCA Australia says sitting quietly reveals more than handling, because mice hide illness.
  2. Weigh. Pop each mouse in a small tub on kitchen scales and write the weight down. Steady loss is often the first sign of trouble.
  3. Eyes, nose and ears. Look for discharge, crusting, redness or squinting.
  4. Teeth. Gently lift the lip. The front teeth should meet neatly and be yellow to orange.
  5. Coat and skin. Part the fur on the neck and shoulders for scabs, specks or redness.
  6. Feel all over. Run your fingers along the body, belly and legs for lumps or tender spots.
  7. Bottom, feet and tail. Check for a dirty bottom, sore feet and rings or wounds on the tail.

Take a cage mate to every vet visit. RSPCA Australia warns that a mouse coming home smelling of the vet can be attacked by its own group, and The Crittery says company helps a sick mouse recover.

How do you keep pet mice healthy?

Most illness in mice is prevented by a good home. The MSD Veterinary Manual says mice rarely get sick when housing, diet and hygiene are right.

  • A complete nugget diet, about 3 to 5 g (0.1 to 0.2 oz) each a day, as in our pet mouse diet guide; obesity is a common problem.
  • Things to gnaw every day, so front teeth wear down.
  • Stable groups of the same sex, since stress and fighting both cause illness.
  • A temperature of 18 to 26°C (64 to 79°F) and humidity of 30 to 70%, says the MSD manual; above 30°C (86°F) risks heat stroke.
  • No grapes, raisins, rhubarb, houseplants or household chemicals within reach.
  • New mice from a good rescue or breeder, checked by a vet before they meet your group.
  • Hands washed before and after handling and between cages.

For the full picture, see our pet mouse care guide.

Mouse health questions

What does it mean when a mouse makes noise when breathing?

Clicking, chattering, wheezing or squeaky breaths usually mean a breathing infection, and the RSPCA lists them as a reason to see a vet. Repeated sneezing, more than a few times in an hour or two, is a warning sign too, says RSPCA Australia. Book a vet the same day, as mice decline fast.

How do I know if my mouse is dying?

A mouse that is very still, cold to the touch, not eating or drinking, breathing slowly or with effort, or no longer moving when touched is seriously ill. Ring a vet straight away. Sometimes a vet can help; if not, they can make sure the mouse is not suffering. Keep it warm, quiet and with its cage mates while you wait.

Can a sick mouse get better?

Many can, especially when seen early. Vets treat breathing infections, mites, wounds, abscesses, overgrown teeth and many lumps. Some conditions, such as mycoplasma infection, are never fully cured but can be kept under control. The MSD Veterinary Manual stresses that early treatment gives the best outcome.

Should I separate a sick mouse from the others?

Usually not. The Crittery warns that loneliness can slow recovery, and RSPCA Australia advises taking cage mates to the vet so scent changes do not cause fighting later. The MSD manual suggests separating mice with some infections, such as Sendai virus or diarrhoea, so follow your vet's advice for each case.

What kind of cage keeps mice healthy?

A large, well-aired barred cage with bars no more than 6 mm apart and a solid floor, kept at 18 to 22°C (64 to 72°F). The MSD Veterinary Manual says reducing damp, draughts and dust may cut breathing infections, and the PDSA warns glass and plastic tanks hold stale air. Use dust-free paper bedding.

Can pet mice make people ill?

Rarely, but it can happen. PetMD notes small animals can carry rat bite fever and salmonella, and the MSD manual lists ringworm and the dwarf tapeworm as able to pass to people. Wash your hands before and after handling, clean cages regularly and see a doctor if a bite becomes red, hot or swollen.

How often should a pet mouse see a vet?

RSPCA Australia advises a vet check soon after you get your mice and then at least once a year, and PetMD suggests a few times a year. In between, check each mouse at home every week. Find a vet who sees mice before you need one, as not all practices do.

Sources

Read next

Pet mouse care: the complete guide

Keep mice in same-sex groups in a big barred cage with deep paper bedding, hides, a solid wheel, about 5 g of mouse nuggets each a day and daily spot cleans.

How long do pet mice live? Lifespan and life stages

Pet mice usually live 1.5 to 2.5 years, a few reach 3; wild house mice average about a year. Good food, company and a cool, clean cage help most.

Pet mouse behaviour and body language explained

Mice talk mostly in ultrasound; the squeaks, chirps, hisses and tail rattles we hear signal mood, and new or repeated noises can mean pain or illness.

Pet mouse temperature guide: too hot, too cold and just right

A mouse's body runs at 36 to 38°C (98 to 101°F). Keep its room at 18 to 22°C (64 to 72°F), never above 26°C (79°F); over 30°C (86°F) risks heatstroke.

Best bedding for pet mice: what is safe and what to avoid

Dust-free, unscented paper or card bedding is best for pet mice, with plain tissue or hay to nest in. Avoid sawdust, cedar, pine, scented types and cotton wool.

Pet mouse diet: what to feed every day

Feed each mouse 3 to 5 g (a level teaspoon) of complete nuggets a day, with small bits of veg inside that allowance, a little protein and fresh water always.