Airways: the lifelong rat issue
Ask rat vets what they treat most and the answer is breathing. Most pet rats acquire airway bacteria early in life and carry them for life, so the goal is managing flare-ups rather than expecting a permanently silent chest. Early signs are sneezing more than usual, a rusty red-brown discharge crusting around the eyes and nose — this is porphyrin, a normal rat secretion that increases when a rat is unwell or stressed — and a coat that looks rough because grooming slips.
Progression is what you are watching for: breathing that becomes audible at rest, crackling or wheezing, sides working visibly, weight loss, and a rat that stops greeting you at the cage door. A rat gasping, mouth-breathing, or hunched and struggling for air is an emergency. Persistent noisy breathing earns a booked vet visit even in a bright rat, because early treatment of a flare-up protects lungs that have to last the rat's whole life. Low-dust bedding, no scented cage sprays, and good ventilation reduce how often airways are provoked.
Lumps: measure first, then show the vet
Female rats commonly develop mammary lumps, which can appear anywhere along the broad band of mammary tissue from neck to groin. Many grow slowly and stay mobile under the skin for a long time; some grow fast, and any lump can eventually ulcerate or grow large enough to impede walking. Size and speed are the information that matters, and both are impossible to judge from memory.
When you find a lump, note the date, the location, and its size against a consistent comparison, then book a vet visit while it is still small — removal, where a vet advises it, is a far smaller procedure on a pea-sized lump than on one that has been watched for months. Any lump that grows quickly, feels fixed rather than movable, breaks the skin, or changes the rat's movement jumps the queue to a prompt visit.
Ageing rats: back legs, kidneys, and balance
Rats age visibly in their final stretch of life. Hind-leg weakness is common in older rats — dragging toes, struggling to climb, scuffed nails — and while it is often a gradual spinal ageing change, sudden weakness or one-sided weakness is different and should be examined. A rat that tilts its head, circles, or loses balance may have an ear infection or, particularly in older rats, a growth affecting balance, and either way it needs a vet assessment rather than assumption.
Older males can lose weight and condition as kidney function declines, sometimes drinking more; gradual weight loss in any senior rat deserves a check rather than being written off as age, because dental problems, lumps inside the body, and airway disease all hide behind the same thinning shape. Check teeth during weekly handling too — a rat dropping food or eating only soft items may have uneven incisors.
The weekly rat check
Rats are social and observant, and the rat that stops appearing for food, stops bruxing and boggling when content, or sleeps through the cage's active hour is giving you a symptom. Weigh weekly, run hands over each rat for lumps during out-of-cage time, listen to breathing in a quiet room, and check eyes for porphyrin build-up. Keep the weights, lump measurements, and breathing notes for each rat in their KinsLe Pet Passport — with several rats in a mischief, the written record is how the quietly declining individual gets noticed in time.