Guinea pigs are gentle, talkative rodents that rarely bite and handle well, which makes them a popular first pet for families. They are also one of the few small mammals with a dietary requirement you cannot improvise: like humans, guinea pigs cannot make their own vitamin C. Get the hay and the vitamin C right and most other things fall into place. Get them wrong and problems appear quietly, because guinea pigs are prey animals that hide illness until it is advanced.
The Vitamin C Requirement
Guinea pigs lack the enzyme needed to synthesize vitamin C, so it must come entirely from the diet, every day. The commonly cited requirement is 10 to 30 mg per kilogram of body weight per day, and sick guinea pigs need more. A deficiency causes scurvy, which shows up as swollen joints, reluctance to walk, bleeding gums, poor coat condition, and a weakened immune system. Untreated, it can be fatal.
- Best food sources: red bell pepper has the highest vitamin C content, followed by parsley, kale, and broccoli. Offer dark leafy greens daily.
- Pellets: guinea pig specific pellets fortified with vitamin C, in small amounts only.
- Storage matters: vitamin C degrades with heat, light, damp, and time, so keep pellets dark and fresh and do not buy in bulk.
- Skip water additives. Vitamin C drops in a bottle degrade within hours and change the taste of the water, which can reduce how much your guinea pig drinks.
Hay Is About 80 Percent of the Diet
Unlimited grass hay is the foundation, not a garnish. It provides the fiber guinea pigs need for digestion and wears down teeth that grow continuously for life. Timothy, oaten, wheaten, meadow, and ryegrass hays are all suitable.
Alfalfa and clover hay are too high in calcium and protein for adults and should be reserved for juvenile animals. Around 15 percent of the diet can be fresh vegetables, roughly half a cup a day of dark leafy greens and peppers, with pellets making up only about 5 percent. Avoid muesli-style mixes, which encourage selective feeding and tend to be low in fiber and high in calories. Never feed iceberg lettuce, potato, onion, chocolate, or dairy. Introduce any dietary change slowly to avoid digestive upset.
Housing: Space, Companions, and Temperature
- Never house a guinea pig alone. They are highly social and become stressed without company. Pairs or small single-sex groups work well.
- Do not house them with rabbits. The dietary needs differ, rabbits can injure or bully a guinea pig, and they can pass infections that are dangerous to guinea pigs.
- Space: a minimum of about 120 x 60 cm for a pair, with one square meter per animal being ideal. Guinea pigs are poor climbers, so length matters far more than height.
- Solid flooring only. Wire-bottom cages cause foot ulcers, a painful condition known as bumblefoot.
- Bedding: paper, hay, straw, or fleece liners. Avoid cedar and pine shavings, which are toxic to small rodents.
- Hiding places: at least one per guinea pig. As prey animals hunted from above, they feel exposed and unsafe without cover.
- Temperature: 18 to 24 degrees Celsius. Guinea pigs are heat sensitive and should not be kept above about 28 degrees, nor in drafts or damp areas.
- Noise: keep them away from loud mechanical noise such as fridges and washing machines.
Daily and Weekly Health Checks
Handling your guinea pig daily makes early problems visible. Check weight weekly and keep a record, since weight loss is often the first sign of illness. Adults normally weigh 700 to 1200 grams.
- Eating, drinking, and passing droppings
- Teeth: drooling, misalignment, or overgrowth
- Eyes and nose: any discharge, sneezing, or labored breathing
- Feet: red or sore foot pads
- Coat: hair loss, matting, or a dull appearance
- Nails: curling or overgrown
- Rear end: keep it clean, especially in older boars
When to Call an Exotic Vet the Same Day
| Sign | Urgency |
|---|---|
| Not eating, or no droppings for 12 to 24 hours | Emergency |
| Diarrhea or soft stool lasting more than a day | Emergency |
| Difficulty breathing, sneezing, or nasal discharge | Same day |
| Swollen joints, reluctance to walk | Same day, possible scurvy |
| Drooling or overgrown teeth | Same day |
| Excessive scratching or patchy hair loss | Soon, likely mites or lice |
An annual check-up with a veterinarian who treats exotics is worth the effort, and any new guinea pig should be examined before being introduced to existing ones. Feed the hay, supply the vitamin C daily, keep the environment stable, and a guinea pig can be a healthy companion for five to eight years.