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Do You Know the Signs of Vitamin D Deficiency?

A lack of the sunshine vitamin is linked to fatigue, aching muscles, and a dozen other symptoms.  

Vitamin D regulates the expression of hundreds of genes and is integral to biological functions that affect every bodily system. Vitamin D insufficiency or deficiency can trigger several generalized symptoms that you may have associated with other health conditions.  

It’s also called the sunshine vitamin since your skin makes vitamin D when exposed to ultraviolet light from the sun.[1] Vitamin D performs many functions within the body, including maintaining adequate levels of calcium and phosphate, essential for normal bone mineralization.[2]  

It helps reduce inflammation, which is necessary for the modulation of cell growth and immune function. Vitamin D also affects genes that help regulate cell differentiation and apoptosis (routine cell death).  

The main indicator of your vitamin D level is 25-hydroxyvitamin D (25OHD). Data collected from the National Health and Nutrition Examination Survey in 2005-2006 showed a deficiency prevalence of 41.6 percent in the U.S. population.[3] However, as I discuss later in this article, as many as 80 percent of people may be deficient in vitamin D.  

It’s important to note that how the measurement of insufficiency and deficiency is defined depends on the serum concentrations used. Some researchers use a level of 20 nanograms per milliliter (ng/mL) or 50 nanomoles per liter (nmol/L); the ng/mL is used most frequently in the United States and nmol/L is the standard in Europe.  

However, GrassrootsHealth Nutrient Research Institute recommends vitamin D serum concentration levels from 40 ng/mL to 60 ng/mL or 100 nmol/L to 150 nmol/L.[4] At this level, the number of people who are likely deficient in vitamin D would be significantly higher.  

14 Signs You Might Have a Vitamin D Deficiency

During cold and flu season, and the COVID-19 pandemic, it is essential to maintain healthy levels of vitamin D to help reduce your risk of viral and bacterial illness.[5,6] A blood test is the best way to determine your vitamin D levels, but here are some symptoms that may indicate your levels are low.  

1. Aching Muscles

Nearly half of all adults are affected by muscle pain.[7] Researchers believe most of those adults are deficient in vitamin D. Some studies have suggested that nerves have vitamin D receptors that affect the perception of pain. In one animal model, research demonstrated a vitamin D-deficient diet can induce deep muscle hypersensitivity that wasn’t connected to low levels of calcium.[8]  

2. Painful Bones

Vitamin D regulates the level of calcium in your body necessary to protect bone health.[9] Vitamin D deficiency can cause your bones to soften a condition called osteomalacia. This may be a precursor to osteoporosis.  

3. Fatigue

This is a common symptom of a variety of different health conditions, including sleep deprivation. Researchers have found that supplementing vitamin D can improve the symptoms of fatigue suffered by cancer patients.[10]  

4. Reduced Muscle Performance

Vitamin D deficiency is as common in athletes as in non-athletes. Vitamin D is crucial for muscle development, strength, and performance. Older adults taking a vitamin D supplement have a reduced risk of falls and improved muscle performance.[12]  

Correction through oral supplementation or sensible sun exposure may reduce symptoms of stress fractures, musculoskeletal pain, and frequent illness. Vitamin D also has a direct effect on muscle performance. In one paper from the Journal of the American Academy of Orthopaedic Surgeons, the author wrote:[13]  

“Higher serum levels of vitamin D are associated with reduced injury rates and improved sports performance. In a subset of the population, vitamin D appears to play a role in muscle strength, injury prevention, and sports performance.”  

5. Brain Health

Vitamin D is also essential for your brain health. Symptoms of deficiency can include dementia caused by an increase of soluble and insoluble beta-amyloid, a factor in Alzheimer’s disease.[14] Research has also found an association with depression15] that may be linked to the function of vitamin D buffering higher levels of calcium in the brain.[16]  

Vitamin D deficiency in pregnant women can increase the risk of autism and schizophrenic-like disorders in the baby.[17] One study of people with fibromyalgia found a vitamin D deficiency was more common in those who had anxiety and depression.[18] Another looked at vitamin D deficiency in obese subjects and found a relationship between low levels of vitamin D and depression.[19]  

6. Poor Sleep

The mechanism linking vitamin D and poor sleep quality hasn’t been identified. But research has found people with low levels of vitamin D have poor quality sleep and a higher risk of sleep disorders.[20]  

7. Sweaty Head

Excessive sweating, especially on your head, or a change in your pattern of sweating, can indicate a vitamin D deficiency.[21]  

8. Hair Loss

Vitamin D is crucial to the proliferation of keratinocytes and plays an important role in your hair cycle. The vitamin D receptor appears to play a role in the anagen phase of hair growth, leading researchers to conclude, “Treatments that upregulate the vitamin D receptor may be successful in treating hair disorders and are a potential area of further study,” they wrote in a study published in Dermatology Online Journal in 2010.[22]  

9. Slow-Healing Wounds

Chronic wounds are a major public health challenge.[23] In the United States, 2 percent of the population is affected by chronic wounds and it is estimated to account for 5.5 percent of the cost of health care in the United Kingdom’s National Health Service (NHS). Vitamin D promotes wound healing and the creation of cathelicidin, a peptide that fights wound infections.[24]  

10. Dizziness

Evidence from animal models suggests that vitamin D is critical in the development of the inner ear,[25] which affects balance and coordination. Analysis of people with vestibular neuritis, characterized by vertigo, showed lower serum vitamin D levels than in people without vestibular neuritis.[26]  

11. Heart Problems

Clinical studies have shown that vitamin D3 improves circulation and can help improve high blood pressure.[27] In one study,[28] researchers discovered that vitamin D3 also has a significant effect on the endothelial cells that line your cardiovascular system. They found that it helped balance concentrations of nitric oxide and peroxynitrite, which improved endothelial function.  

12. Excess Weight

How vitamin D affects obesity hasn’t been identified. However, data do show there is a high probability of deficiency in people who are obese.[29]  

13. Recurring Infections

There have been multiple epidemiological studies that show vitamin D deficiency can increase the risk of infection and raise the severity, particularly in respiratory tract infections.[30] Multiple studies have demonstrated that vitamin D deficiency increases the potential risk for severe disease and mortality, especially in those who are critically ill.[31]  

14. Reduced Cognitive Function

Data shows that vitamin D deficiency increases your risk of dementia twofold[32] and raises your risk of impaired cognitive function.[33]  

COVID-19 and Vitamin D Deficiency

Around 80 percent of people with COVID-19 are deficient in vitamin D.  

Vitamin D plays an important role in the development and severity of many diseases. This is why, from the very beginning of the COVID-19 pandemic, I suspected that optimizing vitamin D levels would significantly lower the incidence of infection and death in the general population.  

Since then, mounting evidence has revealed this is indeed the case as researchers have repeatedly found that higher levels of vitamin D reduce the rate of positive tests, hospitalizations, and mortality related to this infection.  

One study,[34] released in late 2020, assessed the serum 25OHD levels of patients hospitalized with COVID-19 to evaluate the influence it might have on the severity of the disease. The researchers found 82.2 percent of those with COVID-19 were vitamin D deficient (levels lower than 20 ng/mL).  

Interestingly, they also found those who were deficient had a greater prevalence of cardiovascular disease, high blood pressure, high iron levels, and longer hospital stays. A second study[35] found similar results for people who only tested positive for COVID-19.  

It is worth noting, these patients were tested for the illness using the PCR test, which gives notoriously high false-positive results. They didn’t necessarily have symptoms of the illness.  

Recently, data showed people who received supplemental vitamin D3 while hospitalized with COVID-19 had reduced admissions to the ICU by 82 percent and reduced mortality by 64 percent.[36]  

Editor’s note: This preprint study has since been pulled due to “concerns about the description of the research in this paper,”[37] but an archived version is still available. You can read more about the study, from information published before being pulled, at “Vitamin D Supplementation Reduces COVID-19 Deaths by 64%” on  

Dr. Joseph Mercola is the founder of An osteopathic physician, best-selling author, and recipient of multiple awards in the field of natural health, his primary vision is to change the modern health paradigm by providing people with a valuable resource to help them take control of their health. This article was originally published on  

Sources and References

  • [1] National Institutes of Health, Vitamin D    
  • [2] Oregon State University, Vitamin D  
  • [3] Cureus, 2018;10(6)  
  • [4] [42] [44] GrassrootsHealth Magnesium and Vitamin K2 Combined Important for Vitamin D Levels  
  • [5] Harvard Gazette, February 15, 2017  
  • [6] DermatoEndocrinology, 2012;4(2)  
  • [7] [8] Journal of Neuroscience, 2011;31(39)    
  • [9] U.S. Pharmacist, 2009;34(3)  
  • [10] [11] North American Journal of Medical Sciences, 2014;6(8)  
  • [12] Current Opinions in Clinical Nutrition and Metabolic Care, 2009;12(6)  
  • [13] Journal of the American Academy of Orthopaedic Surgeons, 2018;26(8)  
  • [14] Cureus, 2018;10(7) Abstract  
  • [15] Neuropsychiatry, 2017;7(5)    
  • [16] [17] Cureus, 2018;10(7)  
  • [18] Clinical Rheumatology, 2007;26:551  
  • [19] Journal of Internal Medicine, 2008;  
  • [20] Nutrients, 2018;10(10)  
  • [21] Science Care, January 10, 2017  
  • [22] Dermatology Online Journal, 2010;16(2):3    
  • [23] Advances in Wound Care, 2019;8(2)  
  • [24] Today’s Wound Clinic, 2016;10(11)  
  • [25] Biochemical and Biophysical Research Communications, 2016;478(2)  
  • [26] Frontiers in Neurology, 2019;  
  • [27] Science Daily, April 3, 2011  
  • [28] International Journal of Nanomedicine, 2018;13:455    
  • [29] Medicina, 2019;55(9)  
  • [30] Inflammation and Allergy – Drug Targets, 2013;12(4)  
  • [31] Critical Care, 2014;8(6)  
  • [32] University of Exeter, August 6, 2014  
  • [33] JAMA Neurology, 2015;72(11)  
  • [34] The Journal of Clinical Endocrinology and Metabolism, 2020;    
  • [35] JAMA, 2020;3(9):e2019722  
  • [36] Preprints, The Lancet, January 22, 2021;  
  • [37] Europe PMC January 21, 2021  
  • [38] The Sun, February 14, 2021  
  • [39] Irish Times, February 15, 2021  
  • [40] Scandinavian Journal of Rheumatology, 2009;38(2):149  
  • [41] Journal of Nutrition and Metabolism, 2017;2017:6254836  
  • [43]  

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