Feeding your Guinea Pigs - A Balanced Diet (incl. Ca: P Ratio)

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Senior Guinea Pig
Nov 4, 2008
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Cambs, UK
Fresh Fruits & Vegetables for Guinea Pigs
What to feed, and how often.​

Guinea pigs require at least one handful of fresh fruit/vegetables every day. The most well-known reason for this is to ensure an adequate Vitamin C intake, but there are a number of other vitamins and minerals that guineas acquire from their fresh diet that are also important. Understanding the levels of what each food contains is not necessary, so to speak; it is actually very easy to meet your guinea pigs nutritional needs. However there are some things to bear in mind when deciding what’s on your guineas menu.

The key to a healthy fresh diet is to feed a wide variety, and to give everything in moderation. Variety is achieved by feeding at least four different fresh foods each day - this not only covers a wider range of nutrients, but it will also reduce boredom and discourage fussiness. Moderation is achieved simply by being sensible about how much you feed - limiting the amounts of fruit and high sugar/high water foods, only giving a select few sprigs of parsley etc. Do not indulge your guinea too much on one particular food; this may seem a nice idea, but too much of one fresh food (or too much of many foods) can upset the digestive system, leading to softened poops or diarrhea.

There are one or two concerns about some fruits and vegetables that it is worth being aware of (I have put a note beside each of these foods on the list that follows). I have gathered the foods mentioned in TGPF Shopping List and listed them in different categories, which should make choosing your guinea pigs’ diet much simpler.

The optimal selection method is:
2 or 3 foods from the high calcium ranges
2 or 3 foods from the low calcium ranges

Aim for a minimum of 4 different fresh fruits/vegetables daily. It is best to decide on your 4-6 staple foods for the week from the “Daily†list, and if you wish to add some variety, choose one high and one low food from the “Routinely†list. Keep those foods on the “Rarely†list as special treats, given only occasionally.

It is important to work out a diet that suits your guinea pigs. Be aware that it is normal for guineas to have milky/cloudy urine, and for it to dry resembling a powdery substance. The warning signs of far too much calcium in the diet is a thickening of this powder to a sludgy-type substance, and when it feels gritty to the touch. If your guineas are displaying signs of having too much calcium in their diets, limit the high calcium foods to just 1 or 2, keeping the low calcium selection at 2 or 3.

Another point to remember is that dietary factors can influence the colour of the urine. I have highlighted those foods commonly know to turn the urine a orange/red colour. Red urine is often assumed to be a cystitis problem, but consider if your guinea has had any of the foods known to discolour the urine before deciding your course of action.

The information about Fresh Fruits & Vegetables for Guinea Pigs is based on various nutritional factors such as Calcium-Phosphorus Ratio (information below), Vitamin A, sugar and oxalates.

High Calcium Ranges
Cabbage (can lead to gas/bloat in susceptible pigs)
Dandelion Greens
Pak Choi
Red Cabbage (can lead to gas/bloat in susceptible pigs)
Rocket Lettuce
Round Lettuce
Winter Squash

Low Calcium Range
Baby Carrot
Beetroot (can discolour the urine)
Belgian Endive
Broccoli (can lead to gas/bloat in susceptible pigs)
Brussels Sprouts (can lead to gas/bloat in susceptible pigs)
Carrot (can discolour the urine)
Cauliflower (can lead to gas/bloat in susceptible pigs)
Peas in Pods
Peppers (sweet/bell peppers) - red/yellow/green (red pepper can discolour the urine)
Romaine/Cos Lettuce
Savoy Cabbage (can lead to gas/bloat in susceptible pigs)
Summer Squash
Sweet corn (fattening)
Tomato (acid can lead to mouth sores)

Routinely - 2-3 x a week
High Calcium Ranges
Apple (acid can lead to mouth sores)
Broccoli Rabe (can lead to gas/bloat in susceptible pigs)
Garden Cress
Grapefruit (acid can lead to mouth sores)
Kale (can lead to gas/bloat in susceptible pigs)
Lime (acid can lead to mouth sores)
Mustard Greens
Orange (acid can lead to mouth sores)
Tangerine (acid can lead to mouth sores)

Low Calcium Range
Asian Pear
Banana (can lead to “constipationâ€)
Cantaloupe Melon
Honeydew Melon
Nectarine (acid can lead to mouth sores)

High Calcium Ranges
Beet Greens
Collard Greens

Low Calcium Range
Sweet Onion
Sweet Potato

Remember: variety and moderation.


The Calcium-Phosphorus Ratio Explained

Having got a grip on the issues surrounding the calcium-phosphorus ratios in a guinea pig diet myself, I hope to explain it in the simplest way possible to others in order to provide a quick but detailed reference for those looking to discover what foods can be given, and how often. Owners of guinea pigs with bladder issues or similar health concerns in particular may find this interesting and worthwhile reading due to the relevance of "low calcium diets", but please be aware that I do not make any actual medical claims with this article. It is worth being aware of the ratio and how it is calculated; I have already applied it to the food lists above so there is no need to do so yourself, provided to stick to the recommended selection method.

What is the ideal calcium-phosphorus (Ca: P) ratio for guinea pigs?

The ideal ratio for guinea pigs is around 1.3:1. Up to 1.6:1 is also fine. This is to be achieved through the entire fresh fruit and vegetable diet; it is a ratio that is achieved by the overall fresh diet, not individual foods.

A diet too low in calcium can be as bad as a diet too high in calcium. If the ratio is inverted (less calcium than phosphorus), the guinea pigs bone and dental health can suffer. However, too much calcium and the renal system may be overrun by unnecessary, excess calcium.

Why is this ratio relevant to guinea pigs with bladder stones and similar issues?

I can make no medical claims that this diet will directly impact on the formation of renal stones; I can only pass on some of the information I have learned from others. As yet, it is still not fully understood how stones are formed and what aspects may play a part in the formation of them.

What is believed is that stones aren't just formed by excess calcium sitting in the bladder; excess phosphorus can also contribute to the development of stones. In truth, unless a stone is analysed, it shouldn't be assumed to be a calcified substance, as many can turn out to be phosphate stones, or stones containing other substances. To advise a "low calcium diet" if a guinea pig has bladder difficulties (as I, admittedly, have done many a time) is actually incorrect. The advice should to be to address the ratio to ensure the guinea pig has neither too much calcium, nor too much phosphorus, in the diet.

How do you know what the ratio of individual fruits and vegetables are?

By analysing nutritional charts for each of the fruits and vegetables guinea pigs can have, you have access to the levels of the calcium and phosphorus in the foods. You need to be consistent in the weights though - there is no point getting a ratio for 50g of one food and 100g of another - all foods need to have the ratio worked out based on equal weights (all 100g, or all 50g etc.). To find the Ca: P ratio, the basic method is to divide the calcium by the phosphorus.

100g of carrot contains 33mg of calcium, and 35mg of phosphorus.
33 divided by 35 = 0.9.
The Ca: P ratio for carrot is approximately 0.9:1

How do you add up the individual ratios and work out the correct overall ratio?

When you give a variety of fruit and vegetables to your guinea pigs, the Ca: P ratio changes. If you were to feed five different foods daily, you would add up all the figures, then divide the calcium by the number of foods at the end to get the overall ratio.

Carrot - 0.9:1
Cucumber - 0.7:1
Kale - 2.4:1
Broccoli - 0.7:1
Apple - 1.0:1

Add all the calcium numbers up (0.9 + 0.7 + 2.4 etc) and all the phosphorus (1 + 1 + 1 etc.).
The total for the above diet is 5.7:5.

Now divide the calcium by the phosphorus.
5.7 divided by 5 = 1.14.

The Ca: P ratio for the above diet is 1.14:1.

What else should I know?

You do not need to get the ratio perfect - as long as it is somewhere within the range of 1.3:1 to 1.6:1, and you are feeding a good variety and everything in moderation, you can do little more to ensure a balanced diet.


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