Guinea pig care: vitamin C, diet, cage size and daily routine

Guinea pigs are gentle, vocal and long-lived for their size, but they have one quirk that drives most of their care: like people, they cannot make their own vitamin C. Get that right, add plenty of hay and a roomy, clean pen, and you have solved most of the problems vets see in pet guinea pigs. This guide is based mainly on the Merck Veterinary Manual pet owner pages, with hygiene advice from the CDC. For the whole family of small pets, see our small pets library.

Why do guinea pigs need vitamin C every day?

Most mammals make vitamin C in the liver. Guinea pigs lack the enzyme to do so, and they do not store much of it, so a few weeks of a poor diet can lead to deficiency — commonly called scurvy. According to Merck’s page on nutritional problems of guinea pigs, guinea pigs need at least 10 mg of vitamin C per kg of body weight per day, and pregnant females need 30 mg/kg. Because most adults weigh about 1 kg (2.2 lb), about 10 mg per pig per day is a practical floor.

How much vitamin C is in common foods?

You do not need to calculate milligrams at every meal, but it helps to know which foods carry the load. Merck names bell peppers, oranges, strawberries, broccoli, parsley, red cabbage, turnip greens and kale as vitamin C-rich produce. A small strip of sweet bell pepper each day is the easiest habit for most owners, because it is low in sugar and well accepted.

Food	Role in the diet	Note
Bell pepper (red, yellow, green)	Daily vitamin C staple	Low sugar; rotate colors
Broccoli, red cabbage	Occasional vitamin C source	Can cause gas in large amounts
Parsley, kale, turnip greens	Rich in vitamin C	Also high in calcium — not daily
Orange, strawberry	Treat	High sugar; small pieces only
Fortified guinea pig pellets	Backup source	Loses potency as the bag ages

Why pellets alone are not enough

Merck notes that vitamin C breaks down with heat, light and moisture, so fortified pellets can lose a substantial amount within a few months. Buy small bags, check the milling date, store them cool and dry, and treat pellets as a backup rather than your only source. Merck also advises not adding supplements to drinking water and not using routine multivitamins, since some added vitamins can harm guinea pigs. If your vet wants extra vitamin C, they will prescribe a measured dose.

What should a guinea pig eat each day?

Merck’s diet for a guinea pig page lays out a simple structure:

Item	Daily amount	Why
Grass hay (timothy, orchard grass)	Unlimited, available at all times	Fiber for digestion; wears down teeth
Guinea pig pellets	About 2 tablespoons (1/8 cup)	Balanced nutrients and vitamin C
Fresh vegetables	Daily, varied	Vitamin C, moisture, enrichment
Fruit and carrot	Occasional small treat	High in sugar
Fresh water	Always	Clean bottle or heavy bowl

Alfalfa-based pellets, which are higher in calcium, are meant for young, growing or pregnant guinea pigs. Adults usually do better on timothy-based pellets. Merck also lists things to avoid: iceberg lettuce (mostly water), frequent high-calcium greens such as parsley, kale and spinach (excess calcium may contribute to bladder stones), rabbit pellets (not enough vitamin C), and distilled or very mineral-heavy water.

Hay deserves special emphasis. Guinea pig teeth grow continuously, and long-stem hay is what keeps them worn and aligned. A pig that stops eating hay is a pig to watch closely.

Introducing new foods

Change the diet gradually. Add one new vegetable at a time in a small amount, watch the droppings for a day or two, then increase. Sudden changes can upset the gut bacteria guinea pigs depend on.

How big should a guinea pig cage be?

Commercial “starter” cages are often far too small. Merck’s page on providing a home for a guinea pig recommends:

• At least 7 sq ft for one guinea pig — about 42 x 24 inches (106 x 61 cm)
• 2–4 sq ft more for each additional guinea pig
• About 18 inches (46 cm) of height
• A smooth, solid floor — guinea pigs have delicate feet, and wire floors can injure them
• A room temperature of 65–75°F, out of direct sunlight and drafts

Guinea pigs do not jump or climb much, so floor space matters far more than height. A large open pen with a hide box for each animal is better than a tall multi-level cage.

Bedding that is safe

Merck prefers paper-based bedding or kiln-dried pine. Avoid cedar and raw pine shavings (their oils can irritate the lungs), sawdust (a respiratory hazard) and cat litter (indigestible if eaten). Whatever you use, keep it dry — damp, dirty bedding is linked to foot sores and respiratory problems.

Do guinea pigs need a companion?

Guinea pigs are herd animals and are generally happier with another guinea pig. Pairs of females, or a neutered male with females, are common combinations. Introduce new animals on neutral ground with plenty of hay and hiding spots, and supervise the first meetings. Ask your vet about sexing young animals before housing them together — unplanned litters are common.

What does a healthy daily and weekly routine look like?

Merck’s routine care guidance suggests spot-cleaning the cage daily and cleaning it thoroughly every week, plus a checkup at least once a year with a veterinarian experienced with guinea pigs.

Frequency	Task
Daily	Refill hay, serve vegetables with vitamin C, measure pellets, change water, remove wet bedding
Daily	Watch each pig eat, drink, pass normal droppings and move freely
Weekly	Full cage clean, wash bowls and bottle, weigh each pig on a kitchen scale
Monthly	Check nails, teeth (front incisors), coat and feet
Yearly	Veterinary exam with an exotics-experienced vet

Weekly weighing is the single best early-warning tool. A steady drop in weight often shows up before any other sign of illness.

What are the warning signs of illness?

Guinea pigs are prey animals and hide illness well. Contact a veterinarian promptly if you notice:

• Reduced appetite, or not eating hay
• Drooling, overgrown teeth or swelling around the jaw
• Weight loss on the weekly weigh-in
• Swollen joints, limping or reluctance to move (possible vitamin C deficiency)
• Rough coat, small bruises or bleeding under the skin
• Diarrhea or very small, few droppings
• Sneezing, crusty eyes or noisy breathing
• Sore, red feet

Merck lists loss of appetite, dental problems, swollen joints, lameness, rough coat, weight loss, diarrhea and bleeding as signs of vitamin C deficiency. Treatment usually means vitamin C prescribed by a vet, by mouth or injection, plus correcting the diet. A guinea pig that has stopped eating is an emergency — do not wait to see if it improves.

How do you keep your family safe around guinea pigs?

Healthy-looking small mammals can still carry germs such as Salmonella. The CDC’s small mammal guidance recommends washing hands with soap and water after handling the animal, its cage or bedding; keeping pets and their supplies out of the kitchen; cleaning equipment outdoors or in a laundry sink or tub (then disinfecting it); and avoiding kissing or snuggling pets near your face. Children under 5, adults 65 and older and people with weakened immune systems are at higher risk, so supervise handwashing for kids.

Is a guinea pig the right small pet for you?

Guinea pigs suit families who want an interactive pet that is awake during the day and rarely bites. They do need daily fresh food, space and a companion. If you are still comparing species, read our guides to pet rabbit care, which share the hay-first diet but need more room and exercise, and hamster care, a smaller, mostly nocturnal and solitary option. For first-aid basics that apply across species, the toxic foods list is a useful reminder that many household foods are unsafe for pets, and our pet first aid quick guide helps you prepare for emergencies.

Quick checklist for new guinea pig owners

1. Set up a solid-floored pen of at least 7 sq ft per pig before you bring them home.
2. Stock timothy or orchard grass hay, fresh guinea pig pellets and paper bedding.
3. Plan one daily vitamin C vegetable, such as bell pepper.
4. Buy a kitchen scale and record weights weekly.
5. Find a veterinarian who sees guinea pigs before you need one.
6. Teach everyone in the home to wash hands after handling the pets or the cage.

With fresh hay, a daily vitamin C source and a clean, spacious home, guinea pigs are sturdy, social companions that reward a consistent routine.