The most common type of kidney stone is calcium stones. This is a stone that forms when calcium binds with oxalic acid or oxalates. These stones tend to occur because of elevated levels of calcium, oxalates, or both. In order to manage and treat calcium oxalate kidney stones, it's recommended that you reduce your calcium intake and make adjustments to your diet to avoid foods with high oxalate content. This includes foods like iced tea, coffee, spinach, various nuts, and more. But sometimes it's not a dietary issue.