Guinea pig diet: what to feed every day

What food do guinea pigs eat?

Guinea pigs are strict plant-eaters that graze day and night, so their diet is built like a pyramid: a huge base of hay, a smaller layer of fresh vegetables, a little pellet food on top, and fruit only now and then. The UK charities agree on the shape. PDSA and Burgess put hay and grass at 85 to 90% of the diet, and Woodgreen breaks it down as 85% hay, 10% greens and vegetables and 5% pellets.

Timothy hay for guinea pigs: which hay is best?

Timothy hay is the standard choice, and Oxbow calls it the staple grass hay for small plant-eaters. Orchard grass and meadow hay are just as good for everyday feeding. What matters is that it is a grass hay, not a legume hay such as alfalfa, and that it is fresh, sweet-smelling and dust-free.

Too much calcium in adults is linked to bladder stones, which is why Guinea Lynx, VCA and the University of Florida vets all keep adults on grass hay and keep alfalfa as a treat. If your guinea pig turns its nose up at one hay, try a different cut or type before you cut back on the amount. Fresh grazing grass counts too. The RSPCA says to offer it as often as you can, but never lawnmower clippings, which ferment and make guinea pigs ill. Our guide on whether guinea pigs can eat grass covers how to do it safely.

Do guinea pigs have to have hay?

Yes, all day and every day. Guinea pigs' teeth grow all their lives, and long hay is what grinds them down. The fibre in hay also keeps their gut moving. The MSD Veterinary Manual names too little hay as a cause of overgrown teeth and diarrhoea, and PDSA warns that a guinea pig that stops eating can go into gut stasis, which is life-threatening.

So the rule is simple: the hay rack should never be empty. Burgess and Woodgreen both say each guinea pig should eat a pile of hay roughly its own size every day. You cannot overfeed it. If yours is suddenly eating less hay or passing fewer or smaller droppings, ring your vet the same day. Our guinea pig health guide lists the other signs that cannot wait.

How many pellets should a guinea pig eat?

A small amount: about one tablespoon to one eggcup (around 20 g or 0.7 oz) per adult guinea pig a day, according to PDSA, Burgess and Woodgreen. US vets at the University of Florida and the Humane World for Animals say about 1/8 cup. PetMD and Purdue's vets give a larger figure of 1 to 2 oz (28 to 57 g).

We would follow the smaller UK figure for a healthy adult with unlimited hay and daily vegetables. Pellets are there for vitamin C and balance, not to fill them up, and the MSD Vet Manual links too many pellets with diarrhoea and too little hay chewing with dental disease. Growing, pregnant, nursing or underweight guinea pigs may need more, and the RSPCA says to ask your vet about portions for them. If pellets are still in the bowl the next day, you are feeding too many.

What is the best food for guinea pigs?

The best pellet is a plain, grass-based (usually timothy-based) pellet made for guinea pigs, with added vitamin C, where every piece looks the same. That uniform look matters: it stops your guinea pig picking out the tasty bits and leaving the rest. Check the bag before you buy:

• Made for guinea pigs, not rabbits or "small animals" in general
• Grass or timothy based, not alfalfa based, for adults over about 6 months
• Vitamin C added, ideally in a stabilised or protected form
• One kind of pellet, no seeds, nuts, dried fruit or coloured pieces
• A milling or best-before date you can use within about 3 months

Vitamin C fades with time, air, heat and light. VCA and the University of Florida say to use pellets within 90 days of milling, PDSA says within three months of buying, and Woodgreen notes that the vitamin C in an opened bag halves within three months. Buy small bags, keep them sealed, cool, dry and dark, and give a fresh portion each day rather than topping up.

Fresh vegetables: how much and which ones?

Give about one cup of fresh vegetables, greens and herbs per guinea pig per day. PDSA suggests five or six different kinds daily, including some high in vitamin C, and Guinea Lynx suggests splitting it into two or more servings and taking away what is not eaten. The Humane World for Animals gives a slightly smaller range of 1/2 to 1 cup, which suits a small or older guinea pig.

Leafy greens should make up most of it: romaine or other dark leaf lettuce, coriander (cilantro), parsley, rocket (arugula), spring greens and carrot tops. Add something rich in vitamin C, such as bell peppers, and rotate the rest. Our full list of what guinea pigs can eat sorts every common vegetable, fruit and herb into daily, sometimes and never.

How much vitamin C do guinea pigs need?

Most adults need about 10 to 30 mg of vitamin C a day, a figure the University of Florida gives as a daily total. PetMD puts it at 10 mg per kg of body weight for adults, about 20 to 25 mg a day, rising to 30 mg per kg for young and pregnant guinea pigs. VCA gives a wider 10 to 50 mg depending on age, health and stress.

Guinea pigs cannot make their own, so it must come from fresh pellets and vegetables daily. PetMD says signs of scurvy (rough coat, sore joints, poor appetite) can appear after only 2 to 3 weeks on a poor diet. Do not add it to the water: it breaks down fast and can put them off drinking. Our guide to vitamin C for guinea pigs has the best food sources and when a supplement helps.

Can guinea pigs eat bunny food?

No. Rabbit pellets do not contain the vitamin C guinea pigs need, says Burgess, and Guinea Lynx adds that some rabbit foods contain antibiotics that are toxic to guinea pigs. A guinea pig that steals a few mouthfuls from a rabbit's bowl will be fine, but it should never be its regular food. The same goes for "small animal" mixes that are not made for guinea pigs.

Can guinea pigs eat rat food?

No. Rats are omnivores, and rat food is made for them, not for a guinea pig's high-fibre, vitamin C-dependent gut, and many rat foods include grains, seeds or animal protein. VCA says seeds, oats and dry cereals are too high in carbohydrate and fat for guinea pigs, and Oxbow says they cannot digest animal protein well. No source covers rat food by name, so this verdict is reasoned from those points. A stolen mouthful is no emergency; just go back to hay and normal food.

Guinea pig treats: what counts as a good one?

The best treats are pieces of food they already eat: a favourite vegetable, a sprig of herb, a dandelion leaf or a small piece of fruit. PDSA says treats are fine once every week or two, with a little less of their normal food that day, and to skip the sugary, colourful treats sold in pet shops. The Humane World for Animals agrees that shop treats are unnecessary and suggests stuffing a small cardboard tube with fresh hay instead.

Fruit counts as a treat. Keep it to a small piece, once or twice a week, as Woodgreen and PetMD advise. Sugar can upset their gut, and VCA warns that too much fruit can cause serious diarrhoea. For more ways to turn food into play, see our guinea pig enrichment guide.

What food can guinea pigs not eat?

Never feed these. The list comes from PDSA, Burgess and Oxbow's vet-led guidance:

• Potatoes and potato skin, raw or cooked
• Onions, garlic, leeks and chives, which can damage red blood cells
• Avocado, which can harm the heart
• Chocolate, which can be fatal
• Rhubarb, raw and cooked, and its leaves
• Mushrooms
• Tomato leaves, stems and unripe green tomatoes (ripe tomato flesh is fine)
• Meat, eggs, cheese, milk and yoghurt drops
• Bread, pasta, rice, crackers, crisps (chips), biscuits (cookies) and cereal
• Nuts, seeds and peanut butter
• Iceberg and pale lettuce, which give little and can loosen droppings
• Fruit pips, stones (pits) and seeds
• Toxic garden flowers such as buttercups, daffodils, poppies and tulips

If your guinea pig has eaten something on this list, take the rest away, give fresh hay and water, and ring your vet for advice, especially for chocolate, avocado or anything from the onion family. Our page on whether guinea pigs can eat onions explains what to watch for.

How much water do guinea pigs need?

As much as they want, all the time. The RSPCA says to check the water twice a day and stop it freezing in winter, and VCA says to change it and clean the bottle or bowl daily. Burgess recommends a bottle with a solid sipper tube.

How to change your guinea pig's food

Any change, new pellets, a new hay or a new vegetable, should be slow. PDSA and Burgess suggest moving to new pellets over two to four weeks.

1. Start with a mix. Replace about a quarter of the old pellets with the new ones for the first week.
2. Step it up. Move to half and half in the second week, then three quarters new in the third, if droppings stay normal.
3. Finish the switch. Feed only the new food from week three or four. Keep the hay unlimited throughout.
4. Add new veg one at a time. Offer a small piece of one new vegetable and wait a day or two before the next, so you can tell what caused any upset.
5. Watch the droppings. They should stay firm and plentiful. If they turn soft, go back a step and cut back fresh produce for a few days, as the Humane World for Animals suggests.

For the rest of their routine, from cages to company, see our complete guinea pig care guide.