Radishes contain sodium and calcium, which could pose high risk to their digestive system. When guinea pigs eat radishes too much, it is not good for their health. So as much as you want to give the guinea pigs radishes, you shouldn’t do so daily.
You can adopt radishes as a snack for the guinea pigs, occasionally serving the radishes at most two times a week in low quantity and less than ten times a month. When you feed the guinea pig with too many radishes it would only result in health problems.

So while serving the guinea pigs radishes, you should only give them one small radish each, or a half-cup, and when it’s a bigger radish, you should reduce the amount reasonably. Make sure that the radish is served alongside other fresh vegetables that are much richer in vitamin C and contain lesser amounts of sodium and calcium.
While feeding the guinea pig with leaves of radishes, be sure to make it at most two leaves, as the leaves have been found to also contain a substantial amount of calcium. Taking these steps would guarantee your guinea pigs get all the necessary nutrients that are also beneficial to their health.