Guinea pigs eat mostly hay, with fresh vegetables and a small daily portion of pellets. They need vitamin C added to their diet every day.
What food is it?
Can it eat this?
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Vitamin C every day
Guinea pigs need vitamin C in their diet every day (RSPCA Australia). VCA says guinea pigs need 10 to 50 mg of vitamin C a day. It comes from fresh vegetables and herbs and from pellets made for guinea pigs. Vitamin C in pellets doesn’t last: once a bag is opened it halves within three months (Woodgreen), and RSPCA gives a fresh portion each day and uses pellets by their best before date.
How much hay
Woodgreen gives a pile of hay as big as the guinea pig every day, and RSPCA Australia twice its size. RVC’s care sheet suggests a pellet share of 5–10%, and Woodgreen’s 5%, about 20 g a day.
Foods to avoid, by source
RSPCA: iceberg lettuce, potato, garlic, avocado, coconut and citrus fruits, and never lawnmower clippings.
Woodgreen: avocado, canned or frozen fruit and vegetables, chives, coconut, fruit seeds and pips, garlic, hot peppers, leek, onions, onion grass, pineapple leaves, any part of the potato or rhubarb plant, tomato leaves or stalks, and acidic citrus such as limes, lemons and grapefruit.
RSPCA Australia: avocados, chives, coconuts, garlic, grapes, onions, raisins, bread, biscuits and cakes, and grains, seeds and nuts.
VCA: iceberg or head lettuce, oats, seeds, nuts and dry cereals.
RVC's own sheets differ. Its feeding guide says most guinea pigs don't need one, as they get vitamin C from pellets and fresh vegetables, while its care sheet adds a small pinch of crushed vitamin C tablet to the food each day.
Can guinea pigs eat tomatoes?
Woodgreen says the tomato fruit itself is fine, but not the leaves or stalks.
Diet advice comes from RSPCA, RSPCA Australia, Woodgreen (a UK pet charity), the Royal Veterinary College and VCA Animal Hospitals. Checked against published data from RSPCA, Woodgreen Pets Charity, RSPCA Australia, Royal Veterinary College and VCA Animal Hospitals.
See all 5 sources
RSPCA, Guinea pigs: environment, diet and company
Woodgreen Pets Charity, Guinea pigs: housing, day-to-day guide, and poisonous food and plants
RSPCA Australia knowledgebase, Where should I keep my guinea pigs?; What should I feed my guinea pigs?
Royal Veterinary College, Guinea pig care; Guinea pig feeding guidelines, December 2022 (PDFs)
VCA Animal Hospitals, Feeding guinea pigs
General care guidance from animal welfare charities, vets and makers' published sizes. It isn't veterinary advice: if your pet seems unwell or has eaten something it shouldn't, call your vet.