Key Takeaways
- •Rats are masters at hiding illness — by the time symptoms are obvious, the problem is often advanced
- •A weekly health check takes 5 minutes and catches most common problems early
- •Every rat should see an exotic vet shortly after acquisition for a baseline
- •The three most common rat health issues: respiratory disease, tumors, and hind leg degeneration
- •Porphyrin (red discharge around eyes or nose) is a stress/illness indicator, not blood
- •An exotic vet who sees rats regularly is essential — general practice vets often lack rat-specific knowledge
The Challenge With Rat Health
Rats are prey animals. Prey animals are under strong evolutionary pressure to conceal illness — a visibly sick animal is more likely to be targeted by predators. This instinct, while irrelevant in your living room, is deeply embedded. Rats can be significantly ill before you see obvious signs.
This has two implications:
- When you do see obvious illness, take it seriously — it's been developing longer than it looks
- Regular proactive health checks are essential to catch problems before they become obvious
Weekly Health Check Protocol
Once a week, during a handling session, run through this physical assessment. It takes about 5 minutes per rat once you know what you're looking for.
Eyes
Clear and bright. No discharge. Pupils roughly equal.
Watch for:
- Porphyrin: A reddish-orange discharge that looks like blood but is actually a natural secretion from the Harderian gland (behind the eye). Some porphyrin is normal; significant amounts around the eyes and nose are a stress or illness signal.
- Cloudiness (cataracts, common in older rats)
- Swelling around the eye socket
Nose
Moist but not runny. No discharge.
Watch for:
- Porphyrin (see above)
- Clear or colored discharge (infection)
- Sneezing — occasional sneezing is fine; frequent sneezing combined with other signs indicates respiratory disease
Respiratory
Watch the chest while the rat is calm. Breathing should be regular and effortless.
Watch for:
- Labored breathing — visible effort with each breath
- Clicking or crackling sounds (put your ear near their back — this should be silent)
- Fast breathing at rest
- Any audible wheezing or rattling
Respiratory disease is the number one killer of pet rats. Catch it early.
Weight
Handle your rats enough to know what "normal" feels like for each individual. Feel along the spine and ribs.
Watch for:
- Ribs or spine becoming more prominent (weight loss)
- Unusual lumps or masses (tumors)
- Asymmetry (one side swollen)
Weigh your rats monthly on a food scale if possible — small weight changes are hard to feel and easy to track with a number.
Coat
Smooth, clean, and evenly covered. Minimal barbering (the dominant rat sometimes over-grooms others, leaving patches).
Watch for:
- Hair loss beyond normal barbering
- Dull or unkempt appearance (rats who stop grooming are unwell)
- Wounds, scratches, or bite marks from cage-mate conflict
Mobility
Watch them move around during handling and free-roaming.
Watch for:
- Stumbling or loss of coordination
- Dragging hind legs
- Head tilt or circling
- Reluctance to climb or any change in movement patterns
Teeth
Visible incisors should be short, orange-yellow, and even.
Watch for:
- Overgrowth (teeth that have grown past normal length)
- Drooling or dropped food while eating (often a dental sign)
The Most Common Rat Health Issues
Respiratory Disease (Mycoplasma pulmonis)
Nearly all pet rats carry Mycoplasma pulmonis — a bacterial pathogen that lives in the respiratory tract. Most rats coexist with it without obvious symptoms, but stress, immune compromise, or secondary infections can trigger active disease.
Signs: Sneezing, chattering or clicking sounds from the chest, labored breathing, porphyrin discharge, reduced activity.
Treatment: Antibiotics (typically doxycycline and/or azithromycin) can control but not cure mycoplasma. Early treatment during flare-ups significantly extends quality of life.
Tumors
Covered in depth in the tumors guide. Summary: check for lumps every week, especially in females over 18 months. Early detection significantly improves surgical outcomes.
Hind Leg Degeneration (HLD)
A progressive neurological condition that begins with hind leg weakness and eventually renders the hind limbs non-functional. HLD is not painful and progresses over months. Management focuses on maintaining quality of life: easy access to food and water, soft bedding, and monitoring for secondary issues.
Finding an Exotic Vet
Not all vets are created equal when it comes to rats. General practice vets often have limited experience with small mammal medicine, and a vet who treats mostly dogs and cats may not be familiar with rat-specific disease patterns, appropriate antibiotic choices for respiratory disease, or rat surgical techniques.
What to look for:
- A vet who specifically mentions treating rats, ferrets, and other small exotic mammals
- Membership in the Association of Exotic Mammal Veterinarians (AEMV)
- Ask directly: "How many rats do you see in a typical month?" — a vet who sees rats regularly will have a very different skill set
First vet visit: Bring new rats for a baseline examination within the first few weeks of ownership. Establish the relationship before there's an emergency. Know where your exotic vet is before you need them urgently.