Guinea pig first 72 hours: what to check daily, and what to leave alone

Quick answer

A new guinea pig should hide. What it should not do is stop eating. Those two facts do most of the work in the first three days.

A guinea pig arriving in a new home is a prey animal in an unfamiliar burrow. It will hide, freeze, and do most of its eating and moving when you are not in the room. All of that is normal and needs no intervention.

What is not normal is a guinea pig that does not eat. A guinea pig gut has to keep moving continuously, and a stressed animal that stops eating can be in genuine gut stasis within a day. That is why the first 72 hours are about quiet monitoring rather than quiet neglect.

• Weigh on the day of arrival, then daily. This is the single most useful thing you will do.
• Keep feeding exactly what the animal was eating before, and change it slowly over the following weeks.
• Provide unlimited grass hay and a daily source of vitamin C from the first hour.
• Do not introduce a new guinea pig to resident guinea pigs in the first days. Quarantine first.
• Check the sex yourself, or have a vet do it, before an unplanned litter becomes the problem.

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A guinea pig that has not eaten for several hours is not sulking.

Guinea pigs are hindgut fermenters that need near-continuous fibre intake, and they cannot vomit. When intake stops, gut movement slows, gas accumulates and the animal deteriorates quickly. A newly arrived guinea pig that is not eating hay, not drinking and not passing droppings by the end of its first day needs veterinary attention, not another night to settle in.
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Decide in 60 seconds

Before the animal arrives

Set the enclosure up completely the day before.

Floor space matters more than height. A guinea pig needs room to run in a straight line, and cages sold as guinea pig cages are frequently too small. Two hides at minimum, one per pig plus a spare, each with two exits so a pig can never be cornered.

Site it out of the sun and away from draughts and speakers.

Guinea pigs tolerate cold far better than heat, and heat stress is a genuine cause of death. A cage in a sunny window is a hazard even in mild weather. Away from a television or speaker matters too, because guinea pig hearing extends well above ours and constant sound is a stressor you cannot hear.

Get the food they are already on.

Ask the shop, breeder or rescue exactly what pellets and what hay the animal has been eating, and buy some. You will change it later, gradually.

Have a gram scale ready.

Kitchen scales with a bowl on top work. This is a piece of medical equipment for a guinea pig, not an optional extra.

Set up quarantine if you already have guinea pigs.

A separate cage in a separate room, ideally with separate air, and hands washed and clothes changed between them. Several guinea pig problems incubate: respiratory infection, ringworm and mites can all be silently present in an animal that looks perfectly well on collection day.

Day one

Transport quietly and get straight home.

A carrier with a towel and a handful of the hay it is used to. No detours.

Weigh before it goes into the enclosure.

Write the number down. Everything else you do this week is measured against it.

Put the animal in, and then leave the room.

Do not sit and watch. A prey animal will not eat while something large is looking at it. Let it find its hide.

Offer the familiar food, plus unlimited hay and water.

Hay should be the largest thing in the enclosure by volume. If the pig arrived on a coloured muesli mix, keep offering it for now, because an abrupt change to a better food is a common cause of a new pig eating nothing at all.

Provide vitamin C from day one.

Guinea pigs cannot synthesise vitamin C, and shop stock often arrives with reserves already low. Fresh sources such as bell pepper, or a supplement your vet recommends, from the first day. Do not rely on vitamin C added to pellets alone, because it degrades in storage.

Do not bath, brush hard, or handle repeatedly.

There is time for all of that. Handling on day one buys nothing and costs a great deal of trust.

Water available in the form the animal already knows, hay within reach, and a hide it can get into without crossing open ground. That is the whole day one specification.

What normal settling looks like, hour by hour

First few hours. Freezing, hiding, possibly not moving at all. Some pigs will not come out while you are in the room for the first day or two.

First evening and night. Most eating happens now. Check the hay level and the droppings in the morning rather than expecting to watch it eat.

Day two. Should be eating hay reliably, drinking, and producing a normal quantity of droppings. May still bolt for the hide whenever you appear.

Day three. Often the first popcorning, wheeking at the fridge door, or coming out while you are in the room. Some pigs take a fortnight to reach this point, which is fine as long as eating and weight are normal.

What is not a settling-in period

Not eating. Not drinking. No droppings. Laboured or noisy breathing. Diarrhoea. A hunched posture with the eyes half closed. None of these resolve with more time.

The checks that actually matter

Weight, every day, at the same time.

A guinea pig's weight falls before anything else becomes obvious. A downward trend over two consecutive days is a reason to book an appointment even if the animal looks fine. Weigh before feeding, on the same scale, and write it down.

Droppings, counted rather than glanced at.

You are looking for quantity and size, not just presence. Fewer and smaller means less fibre is going through. Soft, stuck or liquid droppings need a vet the same day, because diarrhoea in a guinea pig is dangerous rather than inconvenient.

Hay disappearance.

More reliable than watching the pig eat. If the hay pile is untouched in the morning, something is wrong.

Breathing, listened to in a quiet room.

Guinea pigs are normally silent when breathing. Clicking, crackling, wheezing, or an audible effort are all abnormal, and respiratory infection is one of the most common serious problems in newly acquired guinea pigs. It moves fast.

Eyes, nose and chin.

Crusting around the eyes or nose, or a wet chin and chest, both matter. A wet chin in a new pig can mean dental pain rather than settling in.

The coat and skin.

Hard scratching, thinning hair, scurf or crusty edges to the ears. Mites and ringworm are common in group-housed stock, and ringworm passes to people.

Hay should outweigh everything else in the enclosure. Many guinea pigs arrive eating a coloured mix like this, and the switch to plain pellets is done gradually over weeks, not on the first day.

Sexing, and the pregnancy nobody planned

This is the single most consequential thing to sort out in the first days.

Mixed-sex groups are common in the supply chain, guinea pigs reach sexual maturity young, and sows are frequently sold already pregnant. Owners routinely discover this several weeks later.

Confirm the sex yourself, or have a vet do it.

Do not rely on the label on the pen. If you have taken two animals and you are not certain, separate them now. Separating on day three costs nothing. Separating after the fact does not undo anything.

Why an accidental pregnancy is serious.

Guinea pig pregnancy carries a real risk of pregnancy toxaemia and of difficult birth, particularly in a sow that is very young or that has never bred, and it is not something to manage at home. If a new sow may be pregnant, tell the vet at the first appointment.

Two sows or two boars.

Both can work. Boar pairs are more likely to need space and duplicated resources to stay stable. Neither pairing should be introduced during quarantine.

Company, and why it still waits

Guinea pigs are herd animals. A single guinea pig living alone is under chronic stress, and companionship is not optional enrichment.

But the introduction does not happen this week. Quarantine exists because a newly arrived animal can be incubating respiratory infection, mites or ringworm, and introducing it immediately risks the health of animals that were already fine.

Use the quarantine period to let the new pig settle, establish that it is eating and gaining, and get the first veterinary check done. Then introduce properly, on neutral ground, with the time that requires.

Age and background change the plan

A young pup.

Growing, so weight should be climbing. Needs more energy and more protein than an adult. Also the group most likely to be mis-sexed.

An adult from a shop or breeder.

The standard case. Expect a stable weight and watch for incubating infection.

A rescue or rehomed adult.

Often arrives with an unknown history and sometimes with existing dental disease or a settled vitamin C deficit. Ask for records and get a vet check early. Behavioural settling may take much longer, and that is not a problem as long as eating is normal.

A senior.

Less resilient to a change of diet or environment, more likely to have dental disease, and more likely to lose weight during the transition. Weigh daily for longer than three days.

A pig arriving alone after losing a companion.

Grief-like behaviour is real, and reduced appetite in the first days is common. Monitor intake closely, because the same rules apply regardless of the reason.

The routine for the first three days

A pig that comes out into the open, eats in front of you and explores has settled. Some reach this in three days and some take a fortnight, and both are fine as long as weight holds.

What never to do in the first week

Do not switch the diet abruptly, even to a better one. Improve the food gradually over weeks while the animal is eating reliably.

Do not bathe a new guinea pig. It is stressful, it chills a small animal, and there is almost never a reason.

Do not introduce it to resident guinea pigs, or to a dog or cat, during quarantine.

Do not handle repeatedly to build a bond. Trust is built by predictability and food, not by contact.

Do not assume not eating is shyness. It is the one sign that never gets the benefit of the doubt.

Do not accept a pen label as proof of sex. Check, or have it checked.

Do not house a guinea pig with a rabbit. Different dietary needs, different disease risks, and a rabbit kick can seriously injure a guinea pig.

Do not use a wire-floored cage or a wheel. Guinea pig spines and feet are not built for either.

What the vet will want to know at the first check

When to get help

Contact an exotics or small mammal vet the same day if the guinea pig has not eaten for several hours, is passing no droppings, has diarrhoea, is hunched and quiet, or has any noise or effort in its breathing.

Go urgently for a pig that is cold to the touch, unresponsive, or bloated with a tight abdomen.

Book a routine appointment within the first week for every new guinea pig regardless of how well it seems, to confirm the sex, check the teeth, check for parasites, and set a health baseline while the animal is well.