vitamin D excess
Last edited 05/2022
Excessive vitamin D may be the result of:
- excessive intake:
- self-medication, for example in women concerned about osteoporosis, supplementation during pregnancy (see notes)
- increased production of calcitriol:
- high 1-alpha-hydroxylase in kidney, for example in hyperparathyroidism
- extra-renal production of calcitriol - 1-alpha-hydroxylase activity in granuloma cells, for example in sarcoidosis, sarcomas, some lymphomas.
The features of vitamin D excess are those of hypercalcemia due to increased bone resorption (1).
- Early symptoms of toxicity include symptoms of hypercalcemia such as thirst, polyuria and constipation
- vitamin D toxicity can result in renal failure, which can rapidly become irreversible
- if vitamin D toxicity secondary to excessive supplementation is suspected then vitamin D must be withdrawn and serum calcium and renal function checked urgently, since emergency inpatient care with rehydration is usually indicated (1).
- the Food Standards Agency states that taking 25 mcg (1,000 IU) of vitamin D supplements daily is unlikely to cause any harm in the general population (1,2)
- up to 250 mcg (10,000 IU) can be taken daily for healthy people for up to 16 weeks without toxicity (1)
- pregnancy (2)
- excess vitamin D in animals has been shown to have teratogenic effects. High systemic doses of vitamin D should be avoided during pregnancy
- in consideration of all these factors in mind, the currently recommended dose for supplementation during pregnancy and breast-feeding (10 mcg [400 IU] daily) seems reasonable
vitamin D supplementation and risk of vitamin D excess (toxicity)