Many dialysis patients have low intakes of calcium due to avoidance of foods containing phosphorus and potassium. Lack of calcium can lead to renal osteodystrophy (bone weakening). On the other hand, too much calcium can cause calcification or calciphylaxis (calcium deposits in places such as the heart.[14] Vitamin D is a fat-soluble vitamin, meaning that excessive amounts can be damaging so it should be prescribed and monitored by a doctor.