The use of pharmacological or nutraceutical vitamin d and/or even excessive dietary intake of vitamin d is contraindicated in patients with hypercalcemia, malabsorption syndrome, abnormal sensitivity to the toxic effects of vitamin d, and hypervitaminosis D FDA Label.

Hypersensitivity to vitamin d is one plausible etiologic factor in infants with idiopathic hypercalcemia - a case in which vitamin d use must be strictly restricted FDA Label.

As vitamin d intake is available via fortified foods, dietary supplements, and clinical drug sources, serum concentrations and therapeutic dosages should be reviewed regularly and readjusted as soon as there is clinical improvement FDA Label. Dosage levels are required to be individualized on an individual patient by patient basis as caution must be exercised to prevent the presence of too much vitamin d in the body and the various potentially serious toxic effects associated with such circumstances FDA Label.

In particular, the range between therapeutic and toxic doses is quite narrow in vitamin d resistant rickets FDA Label. When high therapeutic doses are used, progress should be followed with frequent blood calcium determinations FDA Label.

When treating hypoparathyroidism, intravenous calcium, parathyroid hormone, and/or dihydrotachysterol may be required FDA Label.

Maintenance of normal serum phosphorus levels by dietary phosphate restriction and/or administration of aluminum gels as intestinal phosphate binders in those patients with hyperphosphatemia as frequently seen in renal osteodystrophy is essential to prevent metastatic calcification FDA Label.

Mineral oil interferes with the absorption of lipid-soluble vitamins, including vitamin d preparations FDA Label.

The administration of thiazide diuretics to hypoparathyroid patients who are concurrently being treated with vitamin d can result in hypercalcemia FDA Label.

At this time, no long term animal studies have been performed to evaluate vitamin potential for carcinogens, mutagenesis, or fertility FDA Label.

As various animal reproduction studies have demonstrated fetal abnormalities in several species associated with hypervitaminosis D, the use of vitamin d in excess of the recommended dietary allowance during normal pregnancy should be avoided FDA Label. The safety in excess of 400 USP units of vitamin d daily during pregnancy has not been established FDA Label. The abnormalities observed are similar to the supravalvular aortic stenosis syndrome described in infants that is characterized by supravalvular aortic stenosis, elfin facies, and mental retardation FDA Label.

In a nursing mother given large doses of vitamin D, 25-hydroxycholecalciferol appeared in the milk and caused hypercalcemia in her child. Caution is subsequently required when contemplating the use of vitamin d in a nursing woman, and the necessity of monitoring infants' serum calcium concentration if vitamin d is administered to a breastfeeding woman FDA Label.

Adverse reactions associated with the use of vitamin d are primarily linked to having hypervitaminosis D occurring FDA Lanel. In particular, hypervitaminosis D is characterized by effects specific effects on specific organ systems. At the renal system, hypervitaminosis D can cause impairment of renal function with polyuria, nocturne, polydipsia, hypercalciuria, reversible asotemia, hypertension, nephrocalcinosis, generalized vascular calcification, or even irreversible renal insufficiency which may result in death FDA Label. Elsewhere, hypervitaminosis D can also cause CNS mental retardation FDA Label. At the level of soft tissues, it can widespread calcification of the soft tissues, including the heart, blood vessels, renal tubules, and lungs FDA Label. In the skeletal system, bone demineralization (osteoporosis) in adults can occur while a decline in the average rate of linear growth and increased mineralization of bones, dwarfism, vague aches, stiffness, and weakness can occur in infants and children FDA Label. Finally, hypervitaminosis D can also lead to nausea, anorexia, and constipation at the gastrointestinal level as well as mild acidosis, anemia, or weight loss via metabolic processes FDA Label.

The LD(50) in animals is unknown FDA Label.