About feeding a guinea pig
Guinea pigs are herbivores with one crucial quirk: like humans, they cannot make their own vitamin C and must get it from their diet every single day. A hay-based diet plus a reliable vitamin-C source is the foundation of guinea pig health.
How much should a guinea pig eat?
Calorie needs use the veterinary formula 70 × weight(kg)0.75 (the Resting Energy Requirement), multiplied by a lifestyle factor of ×1.4 for a typical guinea pig at the life stage shown. Enter your own animal's details in the calculator for an exact figure.
| Body weight | Daily calories |
|---|---|
| 700 g | 75 kcal |
| 771 g | 81 kcal |
| 843 g | 86 kcal |
| 914 g | 92 kcal |
| 986 g | 97 kcal |
| 1.057 kg | 102 kcal |
| 1.129 kg | 107 kcal |
| 1.2 kg | 112 kcal |
What to feed
Unlimited grass hay forms the bulk of the diet, supplemented with a measured portion of vitamin-C-fortified guinea pig pellets and a daily serving of fresh vegetables high in vitamin C (bell pepper, leafy greens). Rabbit pellets are not a substitute — they lack the added vitamin C.
How often to feed
Hay is free-choice all day. Pellets and fresh veg are given in measured daily portions. Fresh water must always be available.
Common feeding mistakes
- Using rabbit food, which lacks the vitamin C guinea pigs need.
- Relying on vitamin-C drops in water (they degrade quickly) instead of fresh food.
- Feeding unlimited pellets, leading to obesity and selective eating.
- Not providing enough long-strand hay for dental wear.
Weight & health
Vitamin C deficiency (scurvy) causes a rough coat, swollen joints and reluctance to move. Obesity and dental overgrowth are the other common diet-related problems, both prevented by a hay-first diet.
Frequently asked questions
How much should I feed a guinea pig daily?
Unlimited grass hay, about 1/8 cup (roughly 30-40 g) of vitamin-C-fortified pellets, and around one cup of fresh vegetables per guinea pig per day.
How do guinea pigs get vitamin C?
From fresh vegetables (bell peppers are excellent) and fortified pellets. Guinea pigs need roughly 10-30 mg of vitamin C daily and cannot synthesise it themselves.
Can guinea pigs eat rabbit food?
No — rabbit pellets don't contain added vitamin C and may contain ingredients unsuitable for guinea pigs. Always use pellets formulated specifically for guinea pigs.
How much hay does a guinea pig need?
Unlimited timothy or other grass hay, available at all times. It should be the largest part of the diet, keeping teeth worn and the gut moving.