13 signs of widespread vitamin D deficiency

Vitamin D is essential for both mental and physical health, yet deficiencies are extremely common. Avoiding sun exposure, along with aging, dark skin, obesity, diabetes, and genetic variations can make it difficult to convert and activate vitamin D. The same applies to deficiencies in magnesium and zinc. Because active vitamin D is considered a steroid hormone, minor or major deficiencies may result in a wide range of symptoms and diseases.

Most of the body’s cells have vitamin D receptors that regulate around 10 percent of our genes. The form of vitamin D that we produce from sunlight or obtain from supplements is inactive. The liver must first convert it into the form that is stored and measured in the blood. When vitamin D is needed for its many functions, it is then converted into its active steroid form in the kidneys, immune cells, and other cells. However, the winter season, excessive use of high-SPF sunscreen, aging, dark skin, obesity, diabetes, and genetic variations can make it difficult for the body to produce and activate vitamin D. The same is the case with magnesium deficiency, since magnesium is involved in the enzymatic processes of vitamin D metabolism. Too little zinc is also a problem, because zinc functions as a kind of antenna on the cells’ vitamin D receptors. Below, you can read more about 13 signs and diseases that often occur when various cells and tissues lack active vitamin D.

1. Fatigue and sluggishness

It is not known exactly why vitamin D deficiency may cause fatigue and sluggishness. Nonetheless, vitamin D supplementation has shown a positive effect on energy levels in cases of deficiency. This is likely related to vitamin D’s role in the brain, nervous system, and blood sugar regulation.

2. Frequent infections

All white blood cells in the immune system have vitamin D receptors. Antimicrobial peptides in the airways also depend on vitamin D, which is why a deficiency may result in frequent infections. Also, respiratory infections such as colds, influenza, bronchitis, COVID-19, and pneumonia occur more frequently during the winter months, when vitamin D deficiency is more widespread.

3. Chronic inflammation and autoimmune diseases

Vitamin D also helps regulate inflammatory processes and prevent them from becoming unhinged or chronic. Vitamin D deficiency is commonly seen with chronic inflammation, which is associated with “inflammaging” and most chronic diseases. This also includes autoimmune intestinal diseases, rheumatoid arthritis, and multiple sclerosis.

4. Depression

Some studies have shown that vitamin D supplementation may reduce depressive symptoms when a deficiency is present. This is because the cells of the brain and nervous system have vitamin D receptors and are highly dependent on the vitamin. In addition, vitamin D counteracts chronic inflammation in the brain, which is often involved in depression.

5. Blood sugar imbalance, obesity, and diabetes

Stable blood sugar is important to ensure that cells receive a constant supply of energy. Vitamin D helps the pancreas produce insulin, which allows blood sugar to enter the cells. Vitamin D deficiency may therefore increase the risk of insulin resistance, which can lead to reduced satiety. This becomes a vicious cycle, as it increases the risk of obesity and metabolic syndrome, a precursor to type 2 diabetes. People who are overweight or diabetic also have difficulty utilizing and activating vitamin D due to storage in adipose tissue and impaired metabolism in the liver and kidneys.

6. Muscle weakness and muscle pain

Vitamin D is important for muscle function. A deficiency may therefore result in loss of muscle strength, loss of muscle mass, and muscle pain.

7. Neck and back pain

Loss of muscle strength may also affect the muscles of the neck and back, leading to tension and pain. Many patients with vitamin D deficiency specifically complain of lower back pain.

8. Osteoporosis and bone fractures

Vitamin D is important for calcium absorption and bone health. In adults, vitamin D deficiency may cause osteomalacia, which is characterized by soft and demineralized bones with a risk of deformities. The condition also increases the risk of osteoporosis and bone fractures. For reference, bone health also depends on magnesium and vitamin K2, which help clear calcium from the arteries and embed it in the bones.

9. Hair loss

Vitamin D plays a role in hair growth and the hair cycle, including the formation of new hair after natural shedding. Vitamin D deficiency may therefore result in slower hair growth and thinner hair. Alopecia areata is an autoimmune disease in which vitamin D supplementation has shown a positive effect on hair growth.

10. Eczema

Vitamin D is important for the skin and the skin’s immune cells, which act as a natural barrier. Vitamin D deficiency increases the risk of eczema, which is characterized by chronic inflammation, irritation, and swelling.

11. Dental and gum diseases

As mentioned, vitamin D is important for calcium absorption and immune function. This means that vitamin D deficiency increases the risk of poor dental health, cavities, periodontitis, and tooth loss.

12. Incontinence and prolapse

As mentioned, vitamin D is important for muscle function. Deficiency may therefore result in weakened pelvic floor muscles, which support the bladder, uterus, vagina, and rectum. This increases the risk of conditions such as incontinence and prolapse.

13. Rickets

Rickets is a rare childhood disease that causes soft, weak, and deformed bones. The disease, which is caused by prolonged vitamin D deficiency, was especially common among English children who grew up in dark alleyways or worked in mines and therefore did not get enough sunlight.

Facts about deficiency diseases and supplementation

• It is estimated that around half of the world’s population is deficient in vitamin D
• Rickets is considered the classic vitamin D deficiency disease
• As described above, minor or major vitamin D deficiencies may cause many other diseases
• If a vitamin D deficiency is suspected, a blood test may be warranted
• Supplements used to prevent or treat vitamin D deficiency should contain enough vitamin D to optimize blood levels of the nutrient (above 75 nmol/L)
• We also need magnesium and zinc in order to activate and utilize vitamin D.

References:

Dinayinie Ekannayake Mudiyanselage et al. Vitamin D deficiency and disease conditions relevant to: Orthopaedic translation. Journal of Orthopaedic Translation. 2026 Feb

Lauren Oster. 14 signs of vitamin D Deficiency. Health, December 2025

Vanderbilt Univsersty Medical Center. Why your D-vitamin supplements might not be working. ScienceDaily 2025

Tuomas Mikola, et al. The effect of vitamin D supplementation on depressive symptoms in adults: A systematic review and meta‐analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition, 2022.

Katharine Lang. Vitamin D deficiency: Supplements may lower risk of inflammatory diseases. MedicalNewsToday. July 18, 2023