What are the effects of hypervitaminosis D (Vitamin D toxicity)?

From the Guidelines

Hypervitaminosis D is a condition that should be treated immediately by stopping vitamin D supplementation and limiting dietary calcium, with a daily intake not exceeding 4,000 IU unless specifically directed by a healthcare provider for a medical condition. The condition typically occurs when someone takes extremely high doses of vitamin D supplements, usually over 10,000 IU daily for extended periods, rather than from sun exposure or food sources. Symptoms of hypervitaminosis D include nausea, vomiting, weakness, frequent urination, kidney problems, bone pain, and calcium deposits in soft tissues due to elevated calcium levels in the blood (hypercalcemia) 1. Treatment involves immediately stopping vitamin D supplementation, limiting dietary calcium, increasing fluid intake, and in severe cases, using medications like bisphosphonates or corticosteroids to lower calcium levels. In extreme situations, hospitalization may be necessary for IV fluids and medications. The condition occurs because vitamin D is fat-soluble and accumulates in the body, enhancing calcium absorption from the intestines and mobilizing calcium from bones, which can lead to dangerously high blood calcium levels. Some key points to consider in the management and prevention of hypervitaminosis D include:

• Daily vitamin D intake should not exceed 4,000 IU unless specifically directed by a healthcare provider for a medical condition 1.
• Preterm infants on parenteral nutrition (PN) should receive 200-1000 IU/day of vitamin D, term infants up to 12 months of age 400 IU/day, and older children 400-600 IU/day 1.
• Paediatric patients receiving long-term PN should be monitored periodically for vitamin D deficiency, and additional supplementation with vitamin D should be provided if 25(OH) vitamin D serum concentrations are < 50 nmol/L 1.
• Oral supplementation of vitamin D should be considered in patients on partial PN as well as during weaning from PN 1. It is essential to be aware of the risks associated with excessive vitamin D intake and to follow recommended guidelines for supplementation to prevent hypervitaminosis D and its potential complications.

From the Research

Definition and Causes of Hypervitaminosis D

• Hypervitaminosis D is a condition caused by excessive intake of vitamin D, leading to hypercalcemia and other symptoms 2, 3, 4.
• The condition can occur due to prolonged and disproportionate consumption of vitamin D supplements, even without developing hypervitaminosis D 3.
• Exogenous hypervitaminosis D is usually caused by the inadvertent or improper intake of extremely high doses of pharmacological preparations of vitamin D, while endogenous hypervitaminosis D may develop from excessive production of an active vitamin D metabolite or reduced degradation of that metabolite 4.

Symptoms and Diagnosis of Hypervitaminosis D

• Clinical symptoms of vitamin D toxicity include confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration 4.
• Severe hypercalcemia is a hallmark of hypervitaminosis D, and serum 25-hydroxyvitamin D [25(OH)D] concentrations higher than 150 ng/ml (375 nmol/l) are indicative of vitamin D overdosing 4.
• Laboratory testing may reveal asymptomatic hypercalcemia caused by the intake of vitamin D, even in doses recommended for the general population and considered safe 4.

Treatment and Management of Hypervitaminosis D

• Treatment of hypervitaminosis D-induced hypercalcaemia may involve the use of glucocorticoids and bisphosphonates 2.
• Cessation of vitamin D supplements can lead to a decline and normalization of 25(OH)D and urine calcium levels 5.
• Individual responses to supraphysiologic concentrations of vitamin D for extended periods of time vary widely, and defining a toxic concentration of this vitamin is difficult 6.

Prevention and Risks of Hypervitaminosis D

• Increased public awareness of vitamin D-related health benefits may increase the risk of hypervitaminosis D due to self-administration of vitamin D in doses higher than recommended 4.
• Over-the-counter medications would benefit from regulation by the Food and Drug Administration to prevent incidental toxicity 5.
• Prolonged consumption of vitamin D supplementation may induce hypercalcemia, hypercalciuria, and hyperphosphatemia, which are considered to be the initial signs of vitamin D intoxication 3.