The kidneys are safely able to excrete excess calcium when citrates are present. Lemons are rich in citrates , and they will safely transport calcium out of the kidneys and into the bladder. Cranberry juice will make the walls of the bladder smooth, so that they are not irritated.
I have a medical condition which causes me to pass a lot of calcium through my kidneys, too, and a holistic nephrologist told me about these. They are working well for me.