NHS Greater Glasgow & Clyde Area Drug and Therapeutics Committee
Greater Glasgow and Clyde Medicines
Medicines Update

Vitamin D: Prevention & Treatment of Deficiency

Key Points

  • Vitamin D levels should NOT be measured routinely.
  • Vitamin D loading doses may differ depending on indication.
  • Check NHSGGC Formulary for vitamin D preparation of choice prior to prescribing.

The NHSGGC guideline on “Vitamin D prevention and treatment of deficiency in adults” is available on StaffNet. There is a summary of this guideline in the GGC Adult Therapeutics Handbook.

In the general population, vitamin D levels and colecalciferol loading doses are not required, however prescribing of a vitamin D (colecalciferol) supplement may be indicated as detailed in Flowchart 1 of the guideline.

For patients with Chronic Kidney Disease (eGFR<30 ml/min/1.73m2), primary hypoparathyroidism, primary hyperparathyroidism or renal osteodystrophy seek specialist advice.

An audit (n=47) carried out at one NHSGGC hospital site in 2018 highlighted the following issues:

  • Vitamin D blood level – only 30% of levels requested were in accordance with the guideline
  • Loading dose – None of the vitamin D loading doses prescribed were as per guideline
  • Maintenance dose – only 60% of maintenance doses were as per guideline

Further education is required around these areas to improve compliance with the guidelines.


1.  When should Vitamin D levels be measured?

Routine vitamin D levels are not required. Vitamin D levels may be considered if:

a.  A patient has low adjusted serum calcium (<2.1mmol/L) and/or possible osteomalacia

b.  A patient has malabsorption syndrome

c.  Chronic Kidney Disease (eGFR<30ml/min/1.73m2) – only in specialist clinic

A vitamin D level >50nmol/L is considered ‘optimal’. Follow up levels are generally not required for patients with vitamin D deficiency, except for patients with malabsorption with suboptimal vitamin D; repeat testing is only appropriate following a minimum of 6 months of supplementation.  

Examples of vitamin D levels requested in the audit, not in accordance to guidance, included fatigue and back pain – measurement of vitamin D is NOT helpful in these situations.


2.   When is a vitamin D loading dose indicated and what maintenance doses should follow?

Recommended vitamin D loading and maintenance doses in the NHSGGC guideline are as follows (in the context of patients with, or at increased risk of osteoporosis, osteomalacia or fracture):

(If viewing table on a mobile device switch to landscape)


Patient Group


Vitamin  D level (nmol/L)


Colecalciferol loading dose


Colecalciferol maintenance dose

When a Vitamin D level has been checked for recommended indication:

Patients with osteomalacia



300,000 units

Single oral dose or
unlicensed intramuscular (IM) route

Oral doses may also be divided over  6-10 weeks (refer to Adult Therapeutics Handbook guideline)

As directed by specialists




1600-2000 units once daily for 3 months (oral)

800-1000 units once daily (oral)

When a Vitamin D level has been checked for an indication NOT on the recommended list:

Patients with fracture/osteoporosis and for IV zoledronic acid or SC denosumab




100,000 units once only (oral)


800-1000 units once daily (oral) in an appropriate calcium and vitamin D preparation (refer to Formulary).

If hypercalcaemia or if calcium contraindicated, prescribe colecalciferol 800-1000 units once daily (oral).

Any other patient



1600-2000 units once daily for 3 months (oral)

800-1000 units once daily (oral)


Refer to Flowchart 2 of the full guideline for maintenance doses for other indications.


3. What is the current NHSGGC preferred formulary vitamin D preparation of choice?

Formulary status can change, therefore, always check the NHSGGC Formulary prior to prescribing. Increased awareness and use of preferred formulary choices of colecalciferol and calcium/colecalciferol combination preparations is a potential area for cost saving.

Useful links


Published 03/06/2020. Medicines Update blogs are correct at the time of publication.