Question

What is the correct dose of vitamin D?

Daily dosing has been shown to provide more sustainable improvements to vitamin D status than large intermittent doses (annual or quarterly doses).1,2 The NOS cautions3 large doses of vitamin D given intermittently may be ineffective and may increase fracture risk. 

In order to obtain an adequate level of vitamin D, individual patients may require very different doses.3 Dosing should therefore be tailored to the individual needs of each patient.

The reasons for the variance in patient response to oral vitamin D supplementation include: malabsorption, augmented speed of elimination due to certain drugs, compliance, as well as starting base-line level of 25(OH)D (calcidiol).2,4-6 Obesity has been suggested as a limiting factor as vitamin D may be sequestered in adipose tissue.3

Patients in need of rapid correction of vitamin D levels can be given a daily loading dose which should not exceed 4000IU per day7, to provide a total of approxiately 300,000IU over a 10 week period.3,7 e.g. 4000IU per day for 10 weeks (280,000IU) followed by 800IU - 2000IU daily one month after the loading dose has been completed.3

Patients who do not require such rapid correction of deficiency, for example those at risk of vitamin D insufficiency, can be prescribed a daily maintenance dose.3 e.g. 800 - 2,000IU daily.3 

References 

1. Sanders KM et al. JAMA. 2010;303:1815-22.
2. Pekkarinen T et al. Vitamin D3 treatment of elderly people. Clinical Endocrinology, 2010. 72(4):455-461.
3. National Osteoporosis Society. Vitamin D and bone health: A practical clinical guideline for patient management. April 2013.
4. Cannell JJ et al. Diagnosis and treatment of vitamin D deficiency. Expert Opinion. Pharmacotherapy, 2008; 9(1):1-12.
5. Pearce S & Cheetham T. Diagnosis and management of vitamin D deficiency. BMJ, 2010; 340:b5664.
6. Heaney RP et al. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am J Clin Nutr 2003; 77:204-10.
7. Scientific Opinion on the Tolerable Upper Intake Level of Vitamin D. EFSA Journal 2012;10(7):2813