Serum vitamin D levels are classified as:

• < 25 nmol/l = deficient
• 25-50 nmol/l = insufficient
• > 50 nmol/l = adequate

There is marked seasonal variation with lowest levels in winter and spring.

In winter and spring:

• 92% of the Scottish population have a vitamin D level less that 75 nmol/l and
• 24% have a level below 25 nmol/l.

This rises to 75% and 8% in the summer and autumn. 

Only treat deficient levels. Over the counter supplements are recommended for all in the winter and spring.

Note

• Check calcium after 4 weeks of loading dose as can unmask hypercalcaemia
• Avoid loading dose if hypercalcaemia or known renal stones
• If planning to start bisphosphonates, wait until loading course complete
• Stop calcium and vitamin D supplements during loading course
• Repeat vitamin D measurement not needed
• Long term calcium supplements not needed except:
  • frail, elderly, housebound
  • patients with diet low in calcium (can use diet calculator to assess)

When to check vitamin D levels

• All patients beginning osteoporosis treatment should have vitamin D checked at baseline unless decision to give loading dose vitamin D in any case.
• If already receiving treatment for osteoporosis +/- calcium and vitamin D supplements measurement only required if new fracture or hypocalcaemia.

How to treat deficiency

Loading dose course

• Given as above ideally prior to commencing treatment such as bisphosphonates
• If already receiving calcium and vitamin D supplements these must be stopped during loading course (6 weeks)
• Repeat vitamin D level not required following loading course

Maintenance following loading dose course

• For those whose diet is low in calcium or absorption likely to be poor recommend calcium and vitamin D - Adcal D3 2 caplets twice daily or Theical D3 once daily. Consider in:
  • age over 70
  • frail
  • housebound
• Younger, fit active patients whose diet is plentiful in calcium do not require additional calcium - long term excessive calcium can be harmful. Treat with standard vitamin D preparations above.
• You can use diet calculator to assess adequate calcium intake.

Chronic kidney disease

Treatment is generally as above but for patients with eGFR < 30 with secondary hyperparathyroidism, renal may suggest Alfacalcidol instead.

Drug treatments that may cause or exacerbate deficiency

• Anti-convulsants, Corticosteroids. Cholestyramine, HAART, Rifampicin.
• Parenteral treatments for osteoporosis – recheck vitamin D prior to each IV Zoledronic acid and once a year if on Denosumab and compliance of supplements uncertain

Intramuscular vitamin D

For those with deficiency unable to take oral supplements (eg severe malabsorption or liver disease) recommend Ergocalciferol 300.000 units intramuscularly every 6 months.

Because of potentially exorbitant costs and short shelf life ideally this is given in OPD. If given in primary care obtain from hospital pharmacy by request on headed note paper.

When to repeat vitamin D measurement

Not required on treatment unless specific circumstances (eg malabsorption, suspected poor compliance, new low trauma fracture, drug treatments that may cause deficiency). Levels plateau slowly - repeat testing in < 6 months after starting treatment never indicated.