A healthy adult guinea pig needs unlimited grass hay, fresh water, suitable vegetables and a measured portion of guinea-pig pellets, with a reliable daily supply of vitamin C.
Hay is the foundation of the diet. Vegetables add variety and nutrients, while pellets supplement rather than replace hay. Growing, pregnant, nursing or unwell guinea pigs need feeding advice suited to their circumstances.
Keep grass hay available all day
Offer a continuous supply of good-quality grass hay, such as timothy or orchard grass. It provides fibre for digestion and encourages the prolonged chewing guinea pigs need. Replace hay that becomes wet, dirty or spoiled.
Alfalfa is richer in calcium and nutrients. It may be appropriate for growing, pregnant or nursing guinea pigs, but it is not the usual hay for a healthy adult. Discuss the choice with your vet if your guinea pig has urinary, dental or other health problems.
Offer a varied selection of vegetables
Suitable choices include romaine lettuce, arugula, turnip greens and red or green bell pepper. Leafy greens can form the main vegetable selection, with bell pepper contributing vitamin C.
Wash produce and remove spoiled leftovers. Introduce unfamiliar foods gradually rather than changing the whole menu at once. The amount should suit the animal’s size, body condition and overall diet; vegetables should not crowd out hay.
Fruit is unnecessary in the daily routine. Veterinary references differ on occasional fruit treats, but there is no need to rely on sugary foods to provide vitamin C.
Measure pellets instead of repeatedly topping up
Choose plain pellets formulated for guinea pigs and fortified with vitamin C. Avoid mixes containing nuts, seeds, dried fruit or coloured pieces that encourage selective eating. Rabbit food is not an equivalent substitute.
Published portions vary. The University of Florida describes about one-eighth of a cup daily as a usual pellet intake, while Merck’s professional guide gives approximately one to two teaspoons. These are different feeding recommendations, not amounts to combine.
Use the exact product’s instructions as a starting point and ask a guinea-pig-experienced vet to adjust the portion for your animal. Measure consistently and review the amount if weight or hay consumption changes.
Provide a dependable source of vitamin C
Guinea pigs cannot make their own vitamin C. Merck’s professional Housing and Nutrition of Guinea Pigs chapter gives daily requirements of approximately 10–25 mg per kilogram of body weight for adults, and 30 mg/kg or more for growing, pregnant, nursing or ill animals.
Those figures describe nutritional intake from the whole diet. They are not instructions to add that amount as a supplement or to treat a suspected deficiency.
Fresh fortified pellets and suitable vegetables contribute to intake. Check the pellet expiry date and storage instructions, because vitamin C deteriorates over time. Ask your vet whether a separate supplement is needed and which product and amount to use.
Do not rely on vitamin C added to drinking water: it degrades and may make the water less appealing. Avoid giving a multivitamin unless your vet recommends it; unnecessary additional vitamins can be harmful.
Check water and food access for every guinea pig
Provide fresh water continuously. Clean drinking equipment, replace the water daily and check that a bottle’s nozzle releases water properly.
In shared housing, watch each guinea pig eat. A bowl becoming empty does not tell you which animal ate the food. Keep an individual weight record and seek veterinary advice about a downward trend, drooling or difficulty chewing.
Act promptly when appetite changes
Contact a veterinarian immediately if a guinea pig stops eating, eats significantly less or produces markedly fewer droppings. Use the out-of-hours service when necessary. Digestive problems can deteriorate rapidly, and appetite loss may also reflect dental disease or another illness.
Do not delay assessment by repeatedly offering different foods or assuming the animal is being fussy. Bloating, weakness or breathing difficulty adds urgency. Begin assisted feeding, medication or supplements only under veterinary direction.
