Vitamin D Deficiency - Causes

Not ready to share? Read other Patient Comments

If known, what were the causes of your vitamin D deficiency?

Share your story with others:

MedicineNet appreciates your comment. Your comment may be displayed on the site and will always be published anonymously.Patient Comments FAQs

Enter your Comment

Tell us a bit about your background to make your comments more useful to other MedicineNet users. (Optional)

Screen Name: *

Gender of Patient: Male Female

Age Range of Patient:

I am a: Patient Caregiver

* Screen Name will appear next to the published comment. Please do not include your full name or email address.

By submitting your comment, and other materials (collectively referred to as a "Submission") to MedicineNet, you grant MedicineNet permission to use, copy, transmit, publish, display, edit and modify your Submission in connection with its Web site. MedicineNet will not pay you for your Submission. You represent that you have all rights necessary for MedicineNet to use your Submission as set forth above.

Please keep these guidelines in mind when writing your comment:

  • Please make sure you address the question asked.
  • Due to the overwhelming number of comments received, not all comments will be published.
  • When selecting comments to publish, our staff will choose those that are educational and complement the topic. Please try to stay on topic.
  • Your comment may be edited. We would typically edit comments to make them clearer and more readable. We will remove personal information such as last names, email and web addresses, and other potentially harmful information.
  • We will not notify you if your comment has been published. We suggest that you check back on the topic article regularly.
  • We do not provide medical or healthcare advice, treatment, or diagnosis.

Thank you for participating!

I have read and agree to abide by the MedicineNet Terms and Conditions and the MedicineNet Privacy Policy (required).

To prevent our systems from spam, please complete the following prior to submitting your comment.

Please select the white circle:

What causes a vitamin D deficiency?

Do you know your vitamin D level? Do you think that you could be deficient in vitamin D? With plenty of sunshine available, it may surprise you to know that an estimated 1 billion people are deficient or insufficient in vitamin D. This is estimated because undiagnosed vitamin D deficiency is common worldwide.

Limited exposure to the sun

The major source of vitamin D is natural sun, so limiting our exposure to it has the biggest impact on vitamin D deficiency. We have all heard about the dangers of skin cancer and the need for sunscreen to protect us from this disease. Unfortunately, no one discusses the dangers of not getting vitamin D from the sun and ways to compensate for it. Using a sunscreen with SPF of 30 decreases vitamin D synthesis in the skin by more than 95%. Even if you do have some exposure to the sun, the total amount of vitamin D you can produce is affected by the season, time of day, ozone amount, latitude, and number of clouds in the sky. The important thing about using the sun for vitamin D production is to know that less is more. You are better off with short regular exposures to the sun rather than prolonged exposure for many reasons. The process is not as simple as the sun hitting your skin and vitamin D appearing in your blood. What actually happens is that vitamin D3 is first transformed by a process known as hydroxylation in the liver to 25-hydroxyvitamin D3, often written as (25(OH)D3), and then again in the kidney to its active form, 1,25-dihydroxyvitamin D3, written as (1,25(OH)2D3). The level that is checked in your blood is 25-hydroxyvitamin D, often written as 25(OH)D, which includes vitamin D2 and D3. By staying in the sun, you limit this process and can actually get less vitamin D. You also have a lower risk of burning and damaging your skin with short exposures. Getting 10 to 15 minutes of sun exposure a couple of times per week can be enough for many people.

Darker skin

Melanin is what gives skin its color. Lighter skin has less melanin than darker skin. Melanin is able to absorb UVB radiation from the sun and reduce the skin's capacity to produce vitamin D3. People with a naturally dark skin tone have natural sun protection and require at least three to five times longer exposures to make the same amount of vitamin D as a person with a white skin tone.


Research has begun to show a relationship between BMI and vitamin D deficiency. A study done on 2,187 overweight and obese subjects found that those with a BMI above 40 had 18% lower serum vitamin D levels than those with a BMI under 40. Another study done compared the vitamin D levels of 154 obese subjects to those of 148 nonobese subjects and found that the obese subjects' vitamin D levels were 23% lower. Some possible reasons for this are lower intakes of vitamin D, less exposure to sunlight (UV radiation), and a higher distribution volume of vitamin D. Even with exposure to sunlight, there remains a risk for a deficiency. One study tested the blood levels of vitamin D after sun exposure in both obese and nonobese subjects. It found that there was 57% less vitamin D in the blood of the obese subjects. The exact cause is not known. This emphasizes the importance of having your levels checked regardless of your sun exposure or dietary intake.


People with one of the fat malabsorption syndromes (for example, Crohn's disease, celiac disease) and people who have had bariatric surgery are often unable to absorb enough of the fat-soluble vitamin D.


It has been shown that as we age our body has a decreased ability to synthesize vitamin D from exposure to the sun.

Medications and medical conditions

A wide variety of medications, including antifungal medications, anticonvulsants, glucocorticoids, and medications to treat AIDS/HIV can enhance the breakdown of vitamin D and lead to low levels. There is also a loss of vitamin D for those with chronic kidney disease, primary hyperparathyroidism, chronic granuloma-forming disorders, and some lymphomas.

Return to Vitamin D Deficiency

See what others are saying

Comment from: Hadis, 25-34 Female (Patient) Published: April 01

I have vitamin D deficiency. I think it is because of my diet. I am on vegetarian diet and I have a little milk products allergy.

Was this comment helpful?Yes
Comment from: Christina, 45-54 Female (Patient) Published: April 16

I have hypothyroidism. I read people with this condition often are low on D vitamins. I asked my doctor to test me and yes, I"m low. I take 4,000 IU and will retest in 4 months.

Was this comment helpful?Yes


Get the latest health and medical information delivered direct to your inbox!