Adverse effects Health care providers should also be aware of adverse effects when supplementing with vitamin D. The three research groups that provided vitamin D supplementation reported no adverse events in their studies anaseki Holland et al., 2010; Manaseki Holland et al., 2012; Najada et al., 2001). Vitamin D is generally well tolerated, but toxicity causes hypercalcemia. The symptoms of hypercalcemia include constipation, anorexia, nausea, and vomiting initially, and then polyuria, nocturia, and polydipsia after renal impairment (Lewis, 2009). Symptoms of hypercalcemia can be avoided if 25(OH)D levels are monitored and vitamin D dosage is adjusted accordingly. Health care providers should aware of these potential toxicity symptoms and watch for them in their patients.