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)
    • iatrogenic
  • 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    • if vitamin D toxicity secondary to excessive supplementation is suspected then vitamin D must be withdrawn and serum calcium and renal function checked urgently, since emergency inpatient care with rehydration is usually indicated (1).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