New vitamin D deficiency thresholds recommended

The updated NOS guideline on vitamin D and bone health recommends testing plasma 25(OH)D levels only in patients with musculoskeletal symptoms that could be due to vitamin D deficiency, patients with bone diseases that may be improved with vitamin D treatment, and where correcting vitamin D deficiency prior to specific treatment would be appropriate. 

The guideline advises that routine vitamin D testing is generally unnecessary in patients with osteoporosis or fragility fracture where a decision has been made to co-prescribe vitamin D supplementation with an oral antiresorptive treatment.

New thresholds

In addition, the NOS has revised its definition of vitamin D deficiency. 

Plasma 25(OH)D less than 25nmol/L is considered deficiency and should be treated.

Plasma 25(OH)D of 25–50nmol/L may represent an inadequate vitamin D status and treatment is recommended in the setting of:

• fragility fracture, diagnosed osteoporosis or high fracture risk
• treatment with antiresorptive medication
• symptoms suggestive of vitamin D deficiency
• reduced sunlight exposure due to religious/cultural dress code, dark skin, etc.
• raised PTH
• treatment with antiepileptic drugs or oral glucocorticoids

Plasma 25(OH)D greater than 50nmol/L is considered sufficient. 

Prescribing vitamin D

The guideline reiterates that oral colecalciferol (vitamin D3) is the treatment of choice for vitamin D deficiency. Calcitriol and alfacalcidol are not recommended.

A fixed colecalciferol loading phase over 6 to 10 weeks, with a total dose of up to 300,000IU of vitamin D, is recommended for the treatment of symptomatic vitamin D deficiency, before treatment with potent antiresorptive drugs (zoledronate, denosumab or teriparatide), and in other situations requiring rapid correction of inadequate vitamin D status. This should be followed by maintenance therapy equivalent to 20 microgram (800IU) or more daily, given daily or intermittently.

If co-prescribing vitamin D with oral antiresorptive agents, loading is not required.

Adjusted plasma calcium should be checked one month after completing the loading regimen or after starting lower dose vitamin D supplementation. 

Routine monitoring of plasma 25(OH)D is generally unnecessary unless the patient has symptomatic vitamin D deficiency or malabsorption or poor medication adherence is suspected.