What Is Vitamin D Deficiency? Symptoms, Causes, & Treatment Options

Quick Health Scoop

• Vitamin D deficiency affects an estimated 25-40% of U.S. adults [1,2]
• A variety of factors can cause a lack of vitamin D, ranging from not getting enough vitamin D from food to trouble absorbing vitamin D
• Low vitamin D symptoms include fatigue, bone pain, muscle weakness, mood changes, weight gain, hair loss, and other signs
• Options for vitamin D deficiency treatment focus on increasing your vitamin D intake, primarily through supplements and food

While you might know that you can get vitamin D from the sun, you can also get it from a few foods and a vitamin D supplement. Yet 95% of Americans don’t consume enough Vitamin D from their diet alone.[3] In fact, research suggests that 25-40% of U.S. adults have a blood level indicating vitamin D deficiency.[1,2] 

What is vitamin d deficiency? Simply put, when you have low vitamin D, it means that your body doesn’t have enough vitamin D to stay healthy. Vitamin D, a fat-soluble vitamin, helps your body absorb calcium and works in tandem with it to help build strong bones and keep them healthy.[1] When you have weak bones, you’re more likely to develop  rickets.[4] Vitamin D also helps your muscles move, and helps support your immune system.[1]

Learn More: How Vitamin D Supports Your Immune System

But what are normal vitamin D levels and what level is too low? What causes vitamin D deficiency? What are vitamin d deficiency symptoms to look for? And how do you treat low vitamin D levels?

Let’s dig into this important topic that affects so many people in the United States.

Causes of Vitamin D Deficiency 

How do you know if you need vitamin D? Before determining if your level of vitamin D is too low, you need to know what is considered a normal vitamin D level. And the only way to check your vitamin D levels is by getting a blood test. Why do doctors check vitamin D levels? By running a simple blood test that measures the amount of certain nutrients (like vitamin D) in your blood, the doctor can assess if you’re deficient in these nutrients. The blood test measures a form of vitamin D (known as 25-hydroxyvitamin D, or the active form of vitamin D) in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL), where one nmol/L is the same as 0.4 ng/mL.[1]

• Vitamin D deficiency is defined as levels below 20 ng/ml (50 nmol/liter)[12]
• Vitamin D insufficiency is defined as levels from 21–29 ng/ml (525–725 nmol/liter)
• Levels above 125 nmol/L (50 ng/mL) are too high

Vitamin D deficiency may be caused by :[4,5]

• Not getting enough vitamin D from food in your diet
• Not absorbing enough vitamin D from food (a malabsorption issue)
• Not getting enough exposure to sunlight
• Having a liver or kidneys that cannot convert vitamin D to its active form
• Taking medication that interferes with your ability to convert or absorb vitamin D

Some people face a higher risk of vitamin D deficiency and may need more than the recommended dosages above. Who might be at greater risk? [5,6,7,8]

• Breastfed infants
• Older adults
• People who spend most of their time indoors and/or minimize exposure to sunlight
• People with darker skin
• People with certain medical conditions such as
• GI tract diseases (i.e., celiac disease, IBS, Crohn’s disease) 
• Fat malabsorption syndromes (i.e., cystic fibrosis)
• Hyperparathyroidism
• Chronic kidney and liver disease
• Osteoporosis
• Granulomatous diseases (i.e., histoplasmosis, sarcoidosis, tuberculosis)
• Certain lymphomas (i.e., types of cancer)
• People who are overweight or obes
• People who’ve had bariatric surgery
• People who take medication that affects vitamin D metabolism (i.e., cholesterol drugs), antifungal drugs, anti-seizure drugs, glucocorticoids, and HIV/AIDS medicines
• People with a magnesium deficiency 
• People who don’t consume foods that contain vitamin D, such as milk, eggs, and fatty fish (salmon, mackerel), those with lactose intolerance and those who eat a vegan diet
• Pregnant women

Of note, the 2020-2025 Dietary Guidelines for Americans acknowledge that meeting the needs of vitamin D may be especially important during pregnancy. Why? Because the fetus is  dependent on their mother for adequate vitamin D to develop its skeleton and assist calcium absorption. [9] Vitamin D deficiency in pregnancy may increase the risk of preeclampsia and cesarean section. If the mother has vitamin D deficiency, her baby may be at increased risk for rickets.[10] (See below for details.)

Symptoms of Vitamin D Deficiency 

It may be challenging to determine low vitamin D status or a vitamin D deficiency. What are the symptoms of low vitamin D?[4, 6]

• Fatigue 
• Bone or joint pain
• Muscle weakness, aches, or cramps
• Mood changes, such as depression, irritability, or anxiety
• History of falls or bone fractures without significant trauma
• Weight gain
• Hair loss

Vitamin D deficiency can lead to very serious health problems.[4,7,10] 

• Among infants and children, rickets is caused by the deficiency of vitamin D. This rare but serious condition is where bones fail to mineralize. Signs of rickets include delayed growth or incorrect growth patterns, delayed motor skills, muscle weakness, bone pain, and skeletal deformities.
• In adults, a vitamin D deficiency leads to a progressive loss of bone mineral, density resulting in a softening of bones (osteomalacia), bone pain, and increased risk of osteoporosis.
• In children and adults,  muscle weakness and pain are some physical signs that are often seen with vitamin D deficiency.  

Treatment Options for Vitamin D Deficiency 

If you’re diagnosed with vitamin D deficiency, one option is to take a vitamin D supplement.[5] But how much of this nutrient should you take to return to a normal vitamin D level? Check with your doctor or preferred health care provider, who can advise you on the correct dosage of vitamin D to supplement with to meet your individual needs. Another option is a prescription form of vitamin D, which your doctor may suggest. 

In generally healthy adults, the daily amount of vitamin D you need (measured in international units) depends on your age, with recommended amounts below: [12] 

• Birth to 12 months: 400 IU per day
• Children 1+ years: 600 IU per day
• Adults 19-70 years: 600 IU
• Adults 70+ years: 800 IU per day
• Pregnant and breastfeeding women: 600 IU per day

However, if you’ve got a vitamin D deficiency, you’ll likely need more than that. For patients at risk for vitamin D deficiency, the Endocrine Society recommends: [12]

• Birth to 12 months: 400-1,000 IU per day
• Children 1+ years: 600-1,000 IU per day
• Adults 19-70 years: 1,500-2,000 IU
• Adults 70+ years: 1,500-2,000 IU per day
• Pregnant and breastfeeding women 19-50 years: 1,500-2,000 IU per day

For more information, see the guidelines on vitamin D intake from the Endocrine Society in the table below. It is suggested to go back to your doctor for a blood test and have your level re-tested after supplementation.

See full chart of the Vitamin D intakes recommended by the IOM and the Endocrine Practice Guidelines Committee below:[12] 

How To Increase Vitamin D

How can I raise my vitamin D level quickly? First, talk with your health care provider about taking a vitamin D supplement. The recommended daily dose of vitamin D for most healthy adults is 1000-2000 IU, however remember to  keep your health care provider informed and be sure to have your vitamin D blood level re-checked regularly.[6]

In addition to taking a vitamin D supplement, you can also  include more foods containing vitamin D in your diet. Good sources include fatty fish (think mackerel, salmon, trout, and tuna), cod liver oils, beef liver, cheese, egg yolks, and mushrooms, as well as vitamin D-fortified foods (such as cereal, milk and orange juice).

Finally, you can increase your vitamin D intake by spending just 10-15 minutes in the sun without sunscreen, exposing your face, legs, and arms to sun’s ultraviolet B (UVB) rays. In the skin, vitamin D is converted into the active form of vitamin D3. [11]

How long does it take to reverse vitamin D deficiency? By getting your level checked and  supplementing with the right amount , you may see improvements in three to four months.[6] 

The Bottom Line

Up to 40% of U.S. adults have a vitamin D deficiency,[2] and certain people face an even greater risk. A variety of factors can cause a lack of vitamin D, such as an inadequate intake of vitamin D in the diet, malabsorption issues, and lack of sun exposure, to name a few. Symptoms of low vitamin D may include fatigue, bone pain, muscle weakness, and potentially mood changes and other signs. Your healthcare provider can guide you on getting more vitamin D through diet and supplementation.

Continue to check back on the Nature Made blog for the latest science-backed articles to help you take ownership of your health.

Learn More About Vitamins & Supplements:

• What is Folic Acid Deficiency?
• Biotin Deficiency: Everything You Need to Know
• Common Nutrient Shortfalls: Vitamins You Might Be Lacking & Why

This information is for educational purposes only and is not intended to serve as medical advice or a recommendation for any specific product. Consult your health care provider for more information. 

† These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

References 

1. National Institutes of Health. “Vitamin D.” March 22, 2021. Accessed on: September 6, 2021. https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
2. Nutrition Research. “Prevalence and correlates of vitamin D deficiency in US adults.” January 2011. Accessed on: May 28, 2021. https://pubmed.ncbi.nlm.nih.gov/21310306/
3. Nutrients. “Inadequacy of Immune Health Nutrients: Intakes in US Adults, the 2005-2016 NHANES.”  June 2020. Accessed on: September 5, 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7352522/
4. Cleveland Clinic. “Vitamin D Deficiency.” October 16, 2019. Accessed on: September 6, 2021. https://my.clevelandclinic.org/health/articles/15050-vitamin-d--vitamin-d-deficiency
5. MedlinePlus. “Vitamin D Deficiency.” February 28, 2017. Accessed on: September 6, 2021. https://medlineplus.gov/vitaminddeficiency.html
6. Unity Point Health. “How to Spot a Vitamin D Deficiency.” February 28, 2021. Accessed on: September 6, 2021. https://www.unitypoint.org/article.aspx?id=ca7f4766-8ba8-43a2-bbe7-0ef9efab5c6d
7. Oregon State University’s Linus Pauling Institute. “Vitamin D.” February 11, 2021. Accessed on: September 6, 2021. https://lpi.oregonstate.edu/mic/vitamins/vitamin-D#deficiency
8. Harvard T.H. Chan School of Public Health. “Vitamin D.” 2021. Accessed on: September 6, 2021. https://www.hsph.harvard.edu/nutritionsource/vitamin-d/
9. USDA. “2020-2025 Dietary Guidelines for Americans.” December 2020. Accessed on: September 6, 2021. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf
10. Mayo Clinic. “Rickets.” 2021. Accessed on: September 6, 2021.  https://www.mayoclinic.org/diseases-conditions/rickets/symptoms-causes/syc-20351943
11. Skin Cancer Foundation. “Sun Protection and Vitamin D.” May 14, 2018. Accessed on: May 28, 2021. https://www.skincancer.org/blog/sun-protection-and-vitamin-d/
12. 12. The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 7, “Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline.” 1 July 2011, Pages 1911–1930, https://doi.org/10.1210/jc.2011-0385