vitamin d deficiency

Vitamin D Deficiency: Causes, Symptoms and Treatment

March 28, 2016

Vitamin D is the vitamin everyone is talking about these days, especially in the world of bariatric surgery.  Vitamin D is one of four fat-soluble vitamins (the others are vitamins A, E, and K) and is important in bone metabolism and has recently been observed to have anti-inflammatory and immune-supporting properties. Recent findings suggest that low vitamin D levels may increase incidence and mortality from cardiovascular disease and cancer. Current research is studying possible connections between vitamin D levels and medical problems like diabetes, high blood pressure, and autoimmune conditions like multiple sclerosis (MS).

Your muscles need vitamin D to move
Your nerves need vitamin D to help carry information between your brain and all of your body parts
Your immune system needs vitamin D to aid in fighting off bacteria and viruses

Considering all the bodily functions that need Vitamin D, it is important to make sure you are never deficient!

What Causes Vitamin D Deficiency?

Vitamin D deficiency can occur for a variety of reasons

  • Dietary intake is lower than recommended intake over time
  • Sunlight exposure is limited
  • The kidneys cannot convert vitamin D from its inactive to active form
  • Absorption of vitamin D in the digestive tract is inadequate

Obesity may also increase the risk of a vitamin D deficiency. Greater amounts of subcutaneous fat hold on to more vitamin D and also alter its release into circulation, which results in lower vitamin D levels. Post-gastric bypass patients can become vitamin D deficient over time because the part of the upper small intestine where vitamin D is absorbed is bypassed.

Rickets (in children) and osteomalacia (adults) are the most common vitamin D deficiency diseases. Osteomalacia results in weak bones and symptoms include bone pain and muscle weakness. Tiredness and general achiness and pain are the most common symptoms of vitamin D deficiency, although some do not experience any symptoms.

How is Vitamin D Deficiency Diagnosed?

The best way to check your vitamin D status is through laboratory work, specifically the form of vitamin D found in the blood, 25-hydroxyvitamin D. This value is expressed in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL). 1 nmol/L = 0.4 ng/mL. Your primary care physician or your bariatric surgeon can order this for you.

Generally, levels below 30 nmol/L (12 ng/mL) are too low for overall or bone health, and levels above 125 nmol/L (50 ng/mL) are likely too high. A value of 50 nmol/L or higher (20 ng/mL or higher) is sufficient for most people. Please keep in mind these are general guidelines, your surgeon or the laboratory where you get your laboratory work done may vary slightly from these values. Many Americans are vitamin D deficient while almost no one has a vitamin D level that is too high.

What is the Treatment for Vitamin D Deficiency?

Typically, treatment for vitamin D deficiency is a 50,000 International Units (IUs) vitamin D2 supplement given once weekly for eight weeks. This is only available as a prescription. Lower dose supplements, ranging from 400-5000 IUs are available over the counter. Most bariatric surgeons recommend 2000-5000 IUs daily to maintain adequate vitamin D levels. You can obtain vitamin D in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is present in some plants and fatty fish. Vitamin D3 is synthesized in the skin by sunlight.

Food Sources of Vitamin D

The flesh of fatty fish (salmon, tuna, and mackerel) is one of the best food sources of naturally occurring vitamin D. Beef liver, cheeses, and egg yolks also provide small amounts of vitamin D. However, fortified foods provide most of the vitamin D in the American diet, most notably the addition of vitamin D to milk and orange juice. Vitamin D can also be found added to many breakfast cereals and to some brands of yogurt, margarine, and soy products. Check food labels of these foods when at the grocery store to see if vitamin D has been added to them!

Sunlight as a Source of Vitamin D

As mentioned previously, vitamin D may also be obtained by direct sunlight exposure. In fact, many people meet at least part of their vitamin D needs this way! However, skin exposed to the sun while indoors through a window will not produce vitamin D, so you have to be outside for vitamin D to be synthesized by your skin. Cloudiness, shade, and having a dark skin can limit the amount of vitamin D the skin is able to produce. It is also to important to remember that too much sun exposure can lead to skin cancer, so it is a good idea to include food sources with vitamin D and/or a vitamin D supplement to get adequate amounts daily.


Vitamin D is an important (and often overlooked) supplement that is necessary for overall health. Many people (especially post-bariatric surgery patients) are vitamin D deficient, so it is important to work with your bariatric surgeon or healthcare provider to get your vitamin D levels checked and work to get your vitamin D to an adequate level through a combination of food sources, supplements, and limited sun exposure. It is of the utmost importance to check for any deficiencies after bariatric surgery.


Kulie, T et al (2009). Vitamin D: An evidence-based review. J Am Board Fam Med. 22: 698-706.
National Institutes of Health (2016). Vitamin D: Fact sheet for health professionals.
National Institutes of Health (2011). Vitamin D: Fact sheet for consumers.

Lauren Robinson


Lauren Robinson, RD is the Lead Dietitian and Manager at Bariatric Dietitian Services. She earned her BS in Nutritional Sciences with an emphasis in Exercise from Oklahoma State University and her MS in Nutrition from Texas Woman’s University. She has worked with over 5000 patients since beginning her career in bariatrics, and especially enjoys helping post-weight loss surgery patients get back on track! Read more articles by Lauren!