Tools for Practice Outils pour la pratique

#106 Vitamin D Levels: Vitamin Do or Vitamin Don’t

In adults, what is the evidence to test serum vitamin D levels?

Routine testing of vitamin D levels is unnecessary.  Laboratories often report serum levels between 50 and 7580 nmol/L as insufficient but this is not supported by consistent or reliable evidence. Additionally, large variability in the test limits interpretation of repeat measurements.  

CFPCLearn Logo

Reading Tools for Practice Article can earn you MainPro+ Credits

La lecture d'articles d'outils de pratique peut vous permettre de gagner des crédits MainPro+

Join Now S’inscrire maintenant

Already a CFPCLearn Member? Log in

Déjà abonné à CMFCApprendre? Ouvrir une session

Target serum level: 
  • An extensive systematic review1 on serum 25-hydroxyvitamin D (25-OHD) suggests levels: 
    • >75 nmol/L “are not consistently associated with increased benefit.” 
    • Above 50 nmol/L are “practically sufficient for all persons.”    
    • Between 30–50 nmol/L places some, but not all, persons at risk for inadequacy.” 
    • <30 nmol/L places one at risk relative to bone health.   
No randomized controlled trials in falls or fractures have investigated treating specific vitamin D level targets  Proportion of population with various levels: 
  • Levels <75–80 nmol/L for Canada, USA, and UK are 97%, 77%, and 87%, respectively.2-4 These are not necessarily concerning based on above systematic review. 
  • Canadian results of potentially concerning levels showed 61% are <50 nmol/L2 and 13% below 40 nmol/L.1 
  • While levels ≤74 nmol/L are considered “insufficient” by some provincial laboratories,5 this is not supported by the evidence. 
  • Every 800 IU of vitamin D increases 25-OHD by 816 nmol/L; however, the dose-response relationship is not directly linear and is affected by many factors such as season, adiposity, and skin pigmentation.1,6 
  • Vitamin D assays have a coefficient of variation that may be as high as 10–20%,1 meaning changes in levels with doses of 800 IU/day may not be discernable due to variability in the test.  
  • TOP guidelines suggest supplementing without testing and exceptions where testing may be helpful are also provided in these guidelines.7   
  • Mega doses of vitamin D (i.e. 150,000 IU every three months) have been associated with increased adverse events, including falls and fractures.8,9  
  • Enrolment in many vitamin D supplementation trials was not based on vitamin D levels and treating on speculation was beneficial.10-12 
  • Vitamin D doses in most trials were not adjusted based on vitamin D levels.13-19 
  • A 25-OHD assay costs $61.32.20 

Latest Tools for Practice
Derniers outils pour la pratique

#367 Oral Calcitonin Gene-related Peptide Antagonists: A painfully long name for the acute treatment of migraines

What are the risks and benefits of ubrogepant for the acute treatment of episodic migraines?
Read Lire 0.25 credits available Crédits disponibles

#366 Looking for Closure: Managing simple excisions or wounds efficiently

What are some options for efficiency in wound closure?
Read Lire 0.25 credits available Crédits disponibles

#365 Shrooms for Glooms: Evidence for psilocybin for depression

What are the benefits and harms of psilocybin for treatment-resistant/recurrent depression?
Read Lire 0.25 credits available Crédits disponibles

This content is certified for MainPro+ Credits, log in to access

Ce contenu est certifié pour les crédits MainPro+, Ouvrir une session

  • Adrienne J Lindblad BSP ACPR PharmD
  • James McCormack BSc(Pharm) PharmD
  • Scott Garrison MD PhD

1. IOM (Institute of Medicine). 2011. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press.

2. Rucker D, Allan JA, Fick GH, et al. CMAJ. 2002; 166(12):1517–24.

3. Hyppönen E, Power C. Am J Clin Nutr. 2007; 85:860–8.

4. Ginde AA, Liu MC, Camargo CAJ. Arch Intern Med. 2009; 169(6):626–32.

5. BC Biomedical Laboratories Adult Reference Ranges. Available at: Last accessed November 18, 2013.

6. Moyad M. Dermatol Nurs. 2009; 21(1):25–30,55.

7. Toward Optimized Practice. Vitamin D Guideline. Available at: Last accessed November 18, 2013.

8. Sanders KM, Stuart AC, Williamson EJ, et al. JAMA. 2010; 303(18):1815–22.

9. Glendenning P, Zhu K, Indjerjeeth C, et al. J Bone Miner Res. 2012; 27(1):170–6.

10. Bischoff-Ferrari HA, Willett WC, Wong JB, et al. Arch Intern Med. 2009; 169(6):551–61.

11. Bischoff-Ferrari HA, Dawson-Hughes B, Willett WC, et al. JAMA. 2004; 291(16):1999–2006.

12. Autier P, Gandini S. Arch Intern Med. 2007; 167(16):1730–7.

13. Chapuy MC, Arlot ME, Duboeuf F, et al. N Engl J Med. 1992; 327(23):1637–42.

14. Meyer HE, Smedshaug GB, Kvaavik E, et al. J Bone Miner Res. 2002; 17(4):709–15.

15. Trivedi DP, Doll R, Khaw KT. BMJ. 2003; 326(7387):469–72.

16. Lips P, Graafmans WC, Ooms ME, et al. Ann Intern Med. 1996; 124(4):400–6.

17. Grant AM, Avenell A, Campbell MK, et al. Lancet. 2005; 365(9471):1621–8.

18. Porthouse J, Cockayne S, King C, et al. BMJ. 2005; 330(7498):1003.

19. Jackson RD, LaCroix AZ, Gass M, et al. N Engl J Med. 2006; 354(7):669–83.

20. British Columbia Medical Association. Vitamin D Testing Protocol. Available at: Last accessed November 18, 2013.

21. Allan GM, Korownyk C. Tools for Practice. Available at: Last accessed January 21, 2014.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.