Lack of vitamin c causes scurvy. This is very rare and generally only occurs in guinea pigs who are not cared for and not fed properly.
Pellets are fortified with vit c and it is in every vegetable so you are highly unlikely to have any problems with vitamin c issues in a cared for piggy on a good diet.
Excess vit c is simply excreted in the urine.
Long term overdosing of vit c through supplementation can cause health problems. If the levels that they become used to through long term supplementation drops (even if the levels are consideres within normal levels for any other piggy) then that can cause a scurvy.
Excess calcium is excreted in the urine. This is normal and seeing patches of white powdery urine is not a problem provided it doesn’t happen a lot and the urine doesn’t feel gritty.
Too much calcium can lead to grit in the urine and formation of bladder stones.
Keeping pellets to just one tablespoon and filtering water is the main thing you can do here. High calcium veg such as spinach, kale and parsley should be kept limited - only small amounts and no more than once a week.
If a piggy had bladder stones symptoms such as pain when peeing and blood in urine would be present (however this is also the symptoms of a simple UTI). Stones would need to be excluded via scans and x rays when symptoms are present. Usually a UTI is treated first though.
Feeding too little calcium can also cause white urine. The balance gets knocked out the other way.
Feed in accordance with our diet guide and you won’t go far wrong.
Long Term Balanced General And Special Needs Guinea Pig Diets