The Adult Guinea Pig Health Rhythm: The Weekly Checks That Catch Problems

Quick answer

Guinea pigs are prey animals and they hide illness with real determination. By the time one looks unwell it has usually been unwell for a while, which is why adult guinea pig care is built around a routine rather than around noticing something.

The routine is short. A weekly weight on a kitchen scale, and a two-minute hands-on check from nose to tail. Between them they catch dental disease, bladder stones, ovarian cysts, sore feet, mites and the boar problems that nobody warns new owners about.

A guinea pig that looks well and a guinea pig that is well are not the same thing. The scale is what tells them apart.

• Weigh weekly, on the same scale, and write the number down. Nothing else is as informative.
• Hay intake is your window onto teeth you cannot see.
• Check the underside of all four feet every week. Sore hocks start as redness and end at the bone.
• Older boars need their perineal sac checked and often emptied. This is a routine job, not an emergency.
• Vitamin C must come from food. Adding it to the water is worse than not adding it.

Decide in 60 seconds

Why weight is the whole system

An adult guinea pig in good health holds a remarkably steady weight. There is little day-to-day variation, so the trend line means something even if the absolute number means nothing to you.

Almost every guinea pig illness reduces intake before it changes appearance. Dental pain stops hay first. Bladder pain reduces appetite. A respiratory infection makes an animal quiet and slow to come out for food. Sore feet stop it walking to the hay rack. Ovarian cysts change behaviour and appetite. All of them appear on the scale before they appear to you.

Weigh at the same time of day, on the same kitchen scale, with the guinea pig in a small tub that has been tared out. Write the number and the date down every time, including the boring weeks. What you are building is not a set of readings but a line, and the shape of that line is what a vet will use.

Think in trends rather than thresholds. A single low reading is noise. Two or three consecutive weekly readings heading downwards is a finding, and it justifies an appointment even in an animal that seems bright.

Soft, dry, non-slip flooring is the single biggest factor in preventing the foot problems that make adult guinea pigs stop moving.

The weekly hands-on check

Do it in the same order every time so nothing is skipped. Sit on the floor with the guinea pig on a towel on your lap.

Eyes.

Clear, bright, both the same. Look for discharge, cloudiness, or a white or grey film. Some guinea pigs have a small fleshy protrusion at the lower inner corner, sometimes called fatty eye or pea eye. It is a bulge of the conjunctival sac, it is usually harmless and lifelong, and it is worth having identified once so that you stop worrying about it.

Nose and front paws.

A clean dry nose. Then look at the inside of the front feet, because guinea pigs wipe their faces with them and crusting there is often the first evidence of nasal discharge.

Incisors.

The front teeth should meet evenly, with the uppers and lowers each of similar length side to side. If one is much longer, or they cross, that is a problem. The cheek teeth, which are the ones that usually cause trouble, cannot be seen at home at all. Hay intake is your proxy for them.

Chin and dewlap.

Run a finger under the jaw. Damp, matted or stained fur there means drooling, and drooling in a guinea pig means oral pain.

Throat and neck.

Feel gently along the underside of the jaw and neck for firm swellings. Enlarged, abscessed lymph nodes present as lumps here and need veterinary attention rather than watching.

Ears.

Look inside for wax, crust or debris. Note any head tilt, which is never normal.

Coat and skin.

Part the fur in several places and look at the skin itself, not the surface of the coat. Scurf, crusting, broken hairs, bald patches. Note the pattern: barbering leaves chewed-short fur where a mouth can reach, mites cause intense scratching and crusting, and symmetrical loss along both flanks in a sow suggests ovarian cysts.

Feet, all four, undersides up.

This is the check most often skipped and one of the most valuable. Healthy soles are smooth, pink or pigmented, and haired at the edges. Early pododermatitis is redness and hair loss on the weight-bearing surface. Later it becomes swollen, ulcerated and painful, and in advanced cases the infection reaches bone. It is caused by damp bedding, wire or hard flooring, obesity and inactivity, and it is far easier to prevent than to treat.

Nails.

Check length and curl. Overgrown nails twist and can grow into the pad. Learn where the quick is by looking at a pale nail in good light; on dark nails, take small amounts frequently rather than large amounts occasionally.

Grease gland.

At the base of the spine, just above the tail area. It secretes a waxy substance, and in some guinea pigs, particularly boars, it accumulates into a sticky crust that mats the fur. Soften with a small amount of a mild, guinea pig-safe cleanser recommended by your vet, leave it briefly, and comb it out gently. Never scrub.

Rear end.

Look at the perineal area, the anus and the genitals. Check for urine scald, matted caecotrophs, discharge and, in warm weather, any sign of fly eggs.

Watch how the animal moves as well as how it looks. Reluctance to walk to the hay is an early sign of both foot and dental problems.

The boar jobs nobody mentions

Perineal sac impaction.

As boars age, muscle tone in the sac just inside the anus declines, and soft faeces and bedding accumulate there instead of being passed. The area becomes distended and unpleasant, and the animal cannot clear it himself.

Check it weekly in any adult boar. If it is full, the sac is gently opened and the contents removed. Your vet or a knowledgeable rescue will show you the technique, which takes seconds once you have seen it done. Doing it regularly is routine husbandry; leaving it leads to inflammation, infection and flystrike.

Hair rings.

A ring of hair, either the boar's own or shed by a cagemate, can wrap around the penis inside the foreskin. It tightens as it accumulates, constricting the tissue, and it causes swelling, pain and difficulty urinating.

Check by gently extruding the penis during the weekly examination, as your vet can demonstrate. A hair ring is removed carefully with lubrication; a tight or established one is a job for a vet rather than for a determined owner.

Diet, and the two things that go wrong in adults

Hay is the diet.

Unlimited grass hay, available all the time, in more than one place. It is the fibre that keeps the gut moving, and it is the chewing that wears the cheek teeth. An adult guinea pig that is not eating a substantial amount of hay every day is heading for a dental or gut problem, whatever else it is eating.

Vitamin C, from food.

Guinea pigs cannot synthesise vitamin C and need a daily supply for life. Fresh sources such as bell pepper and leafy greens, plus a good-quality guinea pig pellet within its shelf life, generally cover it. Pellets lose vitamin C over time, so buy in quantities you will use and store them cool and dark.

Do not add vitamin C to the drinking water. It degrades within hours, it changes the taste, and guinea pigs drink less as a result, which is the opposite of what you want. If a supplement is needed, use a tablet or a direct oral product on veterinary advice.

Calcium and the bladder.

Bladder stones in guinea pigs are largely calcium carbonate and are common. High-calcium foods eaten routinely, alfalfa hay fed to adults rather than to growing or pregnant animals, and hard tap water all contribute. Grass hay rather than alfalfa for adults, moderation with the highest-calcium vegetables, and plenty of water intake all help. Understand that diet reduces risk rather than dissolving existing stones.

Pellets in proportion.

A measured daily amount rather than a full bowl, so that hay stays the bulk of intake.

What changes with age

Adult guinea pigs settle into a stable pattern from a few months old until roughly their fourth year, and the pattern of problems changes after that.

In the adult years, expect to be watching for dental disease from insufficient hay, bladder stones, ovarian cysts in unspayed sows, pododermatitis, and the boar problems above.

Sows that have never been bred commonly develop ovarian cysts in middle age. The picture is symmetrical hair loss along both flanks, crusty nipples, behaviour change including mounting and aggression, and sometimes a swollen abdomen. It is diagnosed on ultrasound and treated surgically or hormonally.

As guinea pigs move into their senior years, arthritis, cataracts, heart disease and reduced ability to reach a high hay rack all appear, and the routine shifts towards making food, water and litter accessible from where the animal now chooses to sit.

What never to do

Do not judge condition by appearance in a long-coated guinea pig. Weigh instead.

Do not add vitamin C to the drinking water.

Do not feed alfalfa hay to healthy adults as the main hay.

Do not clip nails without knowing where the quick is, and do not use human nail clippers on a wriggling animal.

Do not scrub the grease gland or use human degreasing products on it.

Do not ignore an adult boar's perineal sac because it is unpleasant.

Do not assume a guinea pig that eats pellets and vegetables enthusiastically has healthy teeth.

Do not wait for a guinea pig to look ill. By then you are late.

When to get help

Book an appointment for a downward weight trend across consecutive weeks, for a guinea pig that has stopped eating hay while still eating soft food, for drooling or a wet chin, for redness or swelling on the underside of a foot, for lumps under the jaw, or for symmetrical hair loss in a sow.

Go the same day for straining or crying while urinating, blood in the urine, no droppings, a tense abdomen, laboured breathing, or a guinea pig that has eaten nothing.

Go immediately for collapse, open-mouth breathing, or any maggots found on the skin in warm weather.

Steady weight, good hay intake, clean feet and free movement is what the routine is protecting.

Bring the weight record with dates, the monthly overhead photographs, exactly what is fed and how much, the hay type and how much is eaten, the bedding and flooring, and any change in behaviour, drinking or toileting. Expect a full examination including the cheek teeth, the feet, the abdomen and the chest, and expect the vet to want imaging if a bladder stone or an ovarian cyst is suspected.