1. Health
You can opt-out at any time. Please refer to our privacy policy for contact information.

Vitamin D Side Effects


Updated May 16, 2014

  • People who can't properly absorb fat (fat malabsorption)
    Vitamin D requires some dietary fat in order to be absorbed in the small intestine. People with conditions that cause fat malabsorption, such as cystic fibrosis, celiac disease, Crohn's disease, whipple disease, and chronic liver disease, are more prone to vitamin D deficiency. People with kidney disease may not be able to convert vitamin D to its active form.
  • People who are obese
  • Infants who are exclusively breastfed
    Vitamin D requirements for infants can't be met by human breast milk alone. Consult your pediatrician before using vitamin D supplements in infants.

Side Effects

Vitamin D is a fat-soluble vitamin. This means that, if consumed in excess, it can build up in the body and cause toxic symptoms, unlike vitamin C and other water-soluble vitamins. Because the buildup is slow, it can take months or years before toxic levels are reached.

Too much vitamin D can result in high levels of calcium in the blood (hypercalcemia), which can lead to calcium deposits in soft tissues such as the lungs or heart, confusion, kidney damage, kidney stones, nausea, vomiting, constipation, weight loss, and poor appetite. 

Possible Drug Interactions

The combination of vitamin D and calcium should not be taken with thiazide diuretics, because it could lead to excess calcium levels in the body. People taking calcium-channel blockers should not take vitamin D and calcium, unless under a doctor's supervision, because it may interfere with the effect of the medication.

Anti-seizure medications and rifampin (for tuberculosis) may reduce vitamin D levels. 

People with low parathyroid function may be at higher risk of high blood calcium levels while taking vitamin D.

Steroids, laxatives, and cholesterol-lowering drugs may reduce the amount of vitamin D your body can absorb. Ideally, vitamin D should be taken several hours before or after consuming these drugs. 


Cannell JJ, Vieth R, Umhau JC, et al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006; 134:1129-40.

Carrillo AE1, Flynn MG, Pinkston C, Markofski MM, Jiang Y, Donkin SS, Teegarden D. Impact of vitamin D supplementation during a resistance training intervention on body composition, muscle function, and glucose tolerance in overweight and obese adults. Clin Nutr. 2013 Jun;32(3):375-81. doi: 10.1016/j.clnu.2012.08.014. Epub 2012 Aug 31.

Ginde AA, Mansbach JM, Camargo CA, Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009; 169:384-90.

Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. Am J Prev Med. 2007 Mar;32(3):210-6.

Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Arch Intern Med. 2008; 168:1174-80.

Heaney, Robert P. “The Vitamin D Requirement in Health and Disease.” The Journal of Steroid Biochemistry & Molecular Biology 97 (2005):13-9.

Holick MF. Vitamin D. In: Shils M, Olson J, Shike M, Ross AC, ed. Modern Nutrition in Health and Disease, 9th ed. Baltimore: Williams and Wilkins, 1999. 

National Institutes of Health Office of Dietary Supplements. Vitamin D: Dietary Supplement Fact Sheet. 
University of Ottawa Evidence-based Practice Center. Effectiveness and Safety of Vitamin D in Relation to Bone Health. Agency for Healthcare Research and Quality. Aug 2007: 07-E013.

Salehpour A1, Hosseinpanah F, Shidfar F, Vafa M, Razaghi M, Dehghani S, Hoshiarrad A, Gohari M. A 12-week double-blind randomized clinical trial of vitamin D₃ supplementation on body fat mass in healthy overweight and obese women. Nutr J. 2012 Sep 22;11:78. doi: 10.1186/1475-2891-11-78.

Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 91:1255-60. Epub 2010 Mar 10.

Wilkins, Consuelo H. and Yvette I. Sheline, et al. “Vitamin D Deficiency Is Associated with Low Mood and Worse Cognitive Performance in Older Adults.” American Journal of Geriatric Psychiatry 14 (2006): 1032-40.

©2014 About.com. All rights reserved.

We comply with the HONcode standard
for trustworthy health
information: verify here.