“Guinea pigs should eat unlimited grass hay, about one cup of fresh vegetables per pig each day, a small portion of plain guinea pig pellets, and a daily source of vitamin C such as bell pepper. Fruit is an occasional treat. Never feed onions, garlic, potatoes, chocolate, meat, dairy, or iceberg lettuce.”
Feeding a guinea pig well is simple once you understand one thing: guinea pigs are grazers built to eat grass all day, just like their giant cousin, the capybara. Their teeth never stop growing, their digestive systems need constant fiber, and they can’t make their own vitamin C. Get those three things right and you’ve solved most guinea pig diet questions. This guide gives you the full list of safe foods, portion sizes, and what to avoid.
The Ideal Guinea Pig Diet
| Food | How Much | Why |
|---|---|---|
| Grass hay | Unlimited, about 80% of the diet | Fiber for digestion and tooth wear |
| Fresh vegetables | About 1 cup per pig per day | Vitamins, hydration, variety |
| Guinea pig pellets | About 1/8 cup per pig per day | Balanced vitamins and minerals |
| Fruit | A few small pieces a week | Treats and extra vitamin C |
| Fresh water | Always available | Hydration |
Hay: The Foundation
Hay should always be available. Good choices include timothy hay, orchard grass, meadow hay, oat hay, and brome. Mixing types keeps things interesting. Alfalfa hay is higher in calcium and protein, so it’s best for guinea pigs under about six months old and for pregnant or nursing sows. For adults, too much calcium can contribute to bladder stones.
Fresh, green, sweet-smelling hay is best. Avoid hay that’s dusty, moldy, or brown and brittle.
Vitamin C: Non-Negotiable
Guinea pigs, like humans and capybaras, can’t produce vitamin C and must get it from food. A deficiency causes scurvy, with symptoms like swollen joints, a rough coat, lethargy, and poor appetite. Veterinary guidance often suggests roughly 10 to 30 mg of vitamin C per kilogram of body weight per day, more during pregnancy or illness. Ask your vet what’s right for your guinea pig.
The best vitamin C vegetables include:
- Red, yellow, and green bell peppers
- Parsley (in moderation)
- Kale (in moderation)
- Broccoli (small amounts)
- Brussels sprouts (small amounts)
We explain the same vitamin C issue in capybaras in our capybara health guide.
Safe Vegetables for Daily Feeding
- Romaine, green leaf, and red leaf lettuce
- Bell peppers (any color)
- Cilantro
- Cucumber
- Zucchini
- Carrot tops
- Bok choy
- Endive and escarole
- Fennel
- Celery (cut into short pieces to avoid stringy fibers)
Vegetables to Feed in Moderation
These are healthy but high in calcium, oxalates, sugar, or gas-producing compounds. Offer them a few times a week:
- Carrots (sugary)
- Kale, spinach, and parsley (calcium and oxalates)
- Broccoli, cauliflower, and cabbage (can cause gas)
- Tomato flesh (never the leaves or stems)
- Sweet corn and corn husks
- Peas and snap peas
Safe Fruits (Treats Only)
- Apple, without seeds
- Strawberries
- Blueberries
- Orange segments (small amounts)
- Kiwi
- Pear, without seeds
- Melon
- Banana (very small pieces)
Fruit is high in sugar, so keep portions tiny, around a thumbnail-sized piece a couple of times a week.
Foods Guinea Pigs Should Never Eat
- Onions, garlic, leeks, and chives: can damage red blood cells.
- Potatoes and potato peels: contain harmful compounds.
- Avocado: high fat and potentially toxic.
- Chocolate, candy, and sweets.
- Meat, eggs, and dairy: guinea pigs are strict herbivores.
- Bread, crackers, cereal, and pasta.
- Nuts and seeds: choking risk and too fatty.
- Iceberg lettuce: low nutrition and can cause diarrhea.
- Rhubarb and tomato leaves.
- Mushrooms.
- Houseplants and garden plants unless you know they’re safe.
Choosing Pellets
Look for plain, uniform pellets made for guinea pigs, ideally timothy-based for adults and fortified with stabilized vitamin C. Avoid colorful mixes with seeds, nuts, corn, and dried fruit. Guinea pigs pick out the sugary bits and leave the healthy parts behind. Never feed rabbit pellets, which lack the vitamin C guinea pigs need.
Can Guinea Pigs Eat Grass?
Yes, fresh grass is a natural and healthy food. Only offer grass from areas that haven’t been treated with pesticides or fertilizers and that dogs haven’t used. Introduce it gradually, since sudden large amounts can upset digestion. Never feed lawnmower clippings, which ferment quickly.
How to Introduce New Foods
Add one new vegetable at a time in small amounts, and watch droppings for 24 hours. Soft stools mean you should cut back. Wash all produce and serve it at room temperature.
Sample Daily Menu for One Guinea Pig
- All day: unlimited timothy hay
- Morning: 1/8 cup plain pellets
- Evening: a handful of romaine, a few strips of bell pepper, a sprig of cilantro, and a slice of cucumber
- Twice a week: a small strawberry or a thin apple slice
Water
Fresh water should be available at all times. Guinea pigs can use bottles or bowls. Our water bottle vs bowl comparison explains which works best.
How Guinea Pig Diets Compare with Capybaras
Guinea pigs and capybaras share a family and a diet built on grass. Both need constant fiber and both depend on vitamin C from food. Capybaras just eat far more, up to 6 to 8 pounds of vegetation a day. See what capybaras eat and capybara vs guinea pig.
For the rest of your guinea pig’s needs, read our complete guinea pig care guide. If your guinea pig stops eating, it’s an emergency; see guinea pig health problems.
Common Feeding Mistakes
- Running out of hay: even a few hours without hay can upset digestion.
- Too many pellets: leads to obesity and less hay eating.
- Too much fruit: sugar can cause digestive upset and weight gain.
- Too much calcium: heavy daily servings of spinach, kale, or parsley can contribute to bladder sludge and stones in some guinea pigs.
- Sudden diet changes: always switch foods gradually over a week or two.
- Feeding “treat sticks” and yogurt drops: these store-bought treats are often full of sugar and dairy.
Frequently Asked Questions
Can guinea pigs eat carrots every day?
It’s better not to. Carrots are sugary, so a few small pieces a week is plenty.
Can guinea pigs eat bananas?
Yes, but only tiny pieces occasionally because of the sugar.
Can guinea pigs eat cucumber?
Yes. Cucumber is a safe, hydrating vegetable they can eat regularly.
Do guinea pigs need vitamin C supplements?
Many get enough from fresh vegetables and fortified pellets. Ask your vet if a supplement is needed.