Vitamin D Prevention and Treatment of Deficiency in Adults 

This guidance gives a summary of how to treat adults who are at risk of or who are known to have deficient / insufficient levels of vitamin D. It is based on the full NHSGGC guidance, Vitamin D Prevention and Treatment of Deficiency in Adults. 


Deficiency of vitamin D can result in osteomalacia. The prime aim of vitamin D supplementation is to prevent this vitamin D deficiency syndrome and the long-term consequences of it i.e. osteoporosis and increased fracture risk.

In the asymptomatic general population there is no need to measure vitamin D levels, although supplementation may be considered. Refer to flowchart 1 from the NHSGGC guideline, Vitamin D Prevention and Treatment of Deficiency in Adults, for advice on supplementation in the general population.

Assessment and Monitoring

When to Measure Vitamin D

  • In patients with low serum adjusted calcium (<2.1mmol/L) and/or where other blood results suggest possible osteomalacia (see below)
  • Patients with malabsorption syndromes
  • CKD (eGFR <30ml/minute/1.73m2) - measurement of vitamin D in this context should usually be carried out by specialist clinics only.

Follow up measurements are rarely required – seek specialist advice before requesting.

Signs and Symptoms of Osteomalacia

Osteomalacia is clinically characterised by joint and bone pain, and is associated with abnormal biochemistry as follows:

  • high serum alkaline phosphatase
  • low serum phosphate 
  • low / low-normal serum calcium 
  • high plasma parathyroid hormone
  • low serum vitamin D, usually <25nmol/L.

Drug Therapy/Treatment Options

For recommended treatments and dosage regimes in patients with, or at increased risk of, osteomalacia, osteoporosis or increased risk of fracture, please refer to flowchart 2 from the guideline, Vitamin D Prevention and Treatment of Deficiency in Adults. Wherever possible, licensed products should be used in preference to unlicensed preparations. 

Loading Doses

For patients requiring a loading dose of colecalciferol 300,000 units, this can be given as a single dose orally or intramuscularly (IM preparation is unlicensed), but may also be given using one of the following oral regimes (as per Royal Osteoporosis Society Guidance "Vitamin D and Bone Health"): 

  • 50,000 units weekly for six weeks, or
  • 40,000 units weekly for 7 weeks, or
  • 4,000 units daily for 10 weeks.

Maintenance Doses

Where daily supplementation is recommended, the patient can be offered a weekly or twice weekly regime which provides approximately the same total daily dose if preferred.

Calcium and Vitamin D supplementation

From flowchart 2, if a combined calcium and vitamin D preparation is recommended then consult the NHSGGC Adult Formulary for choice.


Guideline reviewed: August 2023

Page last updated: December 2023