Vitamin D Insufficiency

By: Kimberly Dent-Ferguson, MBS, MPH, Research Analyst
Reviewed by: Geetha Bhat, MD Cooper University Hospital and Tara Schmidlen, MS, LCGC, Coriell Institute for Medical Research

What is Vitamin D Insufficiency?

Vitamin D is a fat soluble vitamin which has several important functions in the body. A normal level of Vitamin D is defined as a concentration of 25 hydroxy vitamin D greater than 30ng/ml (75nmol/L)1. Vitamin D also helps absorb calcium and phosphorus from our intestines to maintain strong bones and suppresses the release of the parathyroid hormone, a hormone that in excess can cause bone loss.

Vitamin D insufficiency is defined as having 25 hydroxy vitamin D levels of 20 to 30 ng/ml (50 to 75 nmol/L)1. Vitamin D insufficiency has been associated with decreased bone density called osteopenia and osteoporosis – low bone mass with thinning and fragility of bone which increases the risk for fractures2. Vitamin D insufficiency is related to a number of other disorders, such as type 2 diabetes, cardiovascular disease, increased risk of falls, and cancers of the breast, colon, and prostate.

Vitamin D deficiency is when the level of 25 hydroxy vitamin D in the body is less than 20 ng/ml (50nmol/L)1. Without sufficient vitatmin D, bones can become thin, brittle, or misshapen3.

Vitamin D can be found naturally in foods like salmon, mackerel, cheese and egg yolk, and can be added to others like milk, yogurt, ready-to-eat breakfast cereals, and orange juice. It is also available as a dietary supplement. However, the best source of vitamin D is exposure to sunlight. The body makes vitamin D when sunlight hits the skin. When ultravoilet B light rays penetrate your skin, it converts a form of steroid called a sterol present in the cells, into pre-vitamin D3. Vitamin D3 is carried to your liver and then to your kidneys where it is transformed into its active form of vitamin D. People who don't get enough sunlight or who cover their bodies with sunscreen or clothing are at increased risk of vitamin D insufficiency and should include good sources of vitamin D in their diets or take a high quality vitamin D supplement2.

How Common is Vitamin D Insufficiency?

According to the Institute of Medicine, about 24% of the U.S. population was at risk for vitamin D insufficiency from 2001-20064.

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Learn more about Vitamin D Insufficiency, from symptoms to understanding your risk, through the links below.

Page References

1. Holick, M.F., et al., Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab, 2011. 96(7): p. 1911-30.
2. Harvard Medical School, Vitamin D and your health: Breaking old rules, raising new hopes. Harvard Health Publications, 2009.
3. Zeratsky, K. What are the risks of vitamin D deficiency? 2012; Available from:
4. Looker, A., et al., Vitamin D Status: United States, 2001-2006. U.S. Department of Health and Human Services, 2011. NCHS Data Brief, no. 59.

Symptoms, Diagnosis, Treatment

Learn more about Vitamin D Insufficiency [ Learn More › ]

Risk Factors

Both genetic and non-genetic factors play a role in Vitamin D Insufficiency Learn More› ]

Reduce Your Risk

Risk-reducing behaviors for Vitamin D Insufficiency Learn More› ]

The CPMC Study

Learn how the CPMC Study identifies your risk for Vitamin D Insufficiency Learn More› ]