How does your body feel when you're low on vitamin D?

October 8, 2025 •

5 min read

Globally, vitamin D deficiency is remarkably common, with numerous studies revealing a significant portion of the population has insufficient levels. So, how does your body feel when you're low on vitamin D? The effects can be wide-ranging, impacting your physical energy, mental health, and immune resilience.

Quick Summary

Low vitamin D often manifests as fatigue, bone pain, and muscle weakness. A deficiency can also affect mood, immune function, and increase the risk of certain chronic diseases over time.

Key Points

Fatigue and Tiredness: Persistent, unexplained fatigue that does not resolve with adequate sleep is a primary indicator of low vitamin D.
Bone and Muscle Pain: Aches and weakness in bones and muscles, especially in the back and legs, are common due to vitamin D's role in calcium absorption.
Mood Changes: Low vitamin D levels have been strongly linked to depression, anxiety, and overall mood fluctuations, possibly due to its effect on serotonin production.
Compromised Immunity: Frequent sickness, including colds and infections, can signal a deficiency, as vitamin D is vital for a strong immune response.
Slow Healing: If wounds and injuries take longer than usual to heal, it could be a sign of insufficient vitamin D affecting the skin's recovery processes.
Hair Loss: Severe deficiency is sometimes associated with hair loss, impacting the health of hair follicles.

The Hidden Effects of Low Vitamin D

Vitamin D is a crucial nutrient, often referred to as the "sunshine vitamin" because the body produces it in response to sunlight. While most people associate it with bone health and calcium absorption, vitamin D's roles are far more extensive, influencing the immune system, mood regulation, and muscle function. Unfortunately, many people are unaware they have a deficiency because symptoms can be subtle and easily mistaken for other conditions. This article explores the various ways your body signals that its vitamin D levels are insufficient.

Physical Manifestations of Vitamin D Deficiency

Feeling unwell due to low vitamin D often starts with general physical discomfort that can be difficult to pinpoint. These signs, while common, should not be ignored.

Chronic Fatigue and Tiredness: One of the most frequently reported and noticeable symptoms of low vitamin D is persistent fatigue that doesn't improve with rest. Research has shown a significant link between low vitamin D levels and fatigue, suggesting that supplementing can lead to improved energy levels.
Bone and Joint Pain: Vitamin D is essential for the body to absorb calcium, the primary building block of strong bones. When levels are low, calcium absorption is impaired, which can lead to bone pain, particularly in the back, hips, and legs. In severe cases, this can lead to conditions like osteomalacia (soft bones) in adults and rickets in children.
Muscle Aches and Weakness: Vitamin D plays a key role in muscle contraction and strength. A deficiency can result in muscle pain, weakness, or cramps, especially in the limbs and back. This can increase the risk of falls, particularly in older adults.
Hair Loss: While hair loss can be caused by many factors, a severe vitamin D deficiency has been linked to alopecia, an autoimmune condition causing patchy hair loss. Vitamin D supports hair follicle health, and inadequate levels may impact new hair growth.
Slow Wound Healing: If cuts and scrapes seem to take an unusually long time to heal, low vitamin D could be the culprit. The vitamin is involved in producing compounds critical for the formation of new skin, so a deficiency can slow the body's natural recovery process.

Mental and Emotional Impact

Vitamin D's influence extends beyond physical well-being and can significantly affect your mental state. Several studies have shown a connection between insufficient vitamin D and mood disorders.

Mood Swings and Depression: Research shows a strong correlation between low vitamin D and mood changes, anxiety, and depressive symptoms. Vitamin D helps elevate serotonin levels, the neurotransmitter responsible for mood, happiness, and overall well-being. When vitamin D is insufficient, serotonin production may be affected, contributing to feelings of sadness or depression.
Anxiety: As with depression, low vitamin D has been linked to anxiety. Its anti-inflammatory properties and its influence on brain function may help explain its role in managing anxiety symptoms.

Immune Function and Other Risks

Beyond bone health and mood, low vitamin D can compromise the immune system, making you more susceptible to illness.

Frequent Illness: Vitamin D plays a vital role in modulating the immune system, helping the body fight off bacteria and viruses. A deficiency can weaken your immune response, leading to more frequent colds, flu, or other infections. Studies have shown that vitamin D enhances the antimicrobial effects of immune cells, suggesting that adequate levels are crucial for maintaining a strong defense.
Increased Risk of Chronic Diseases: Long-term vitamin D deficiency is associated with an increased risk of developing various chronic conditions, including cardiovascular disease, autoimmune disorders (like rheumatoid arthritis and multiple sclerosis), and type 2 diabetes.

Understanding the Causes of Deficiency

Vitamin D deficiency is influenced by several factors, including lifestyle, geography, and diet. The primary cause is often a lack of adequate sun exposure, especially during winter months or for those living far from the equator. Age is another factor, as the skin's ability to produce vitamin D from sunlight decreases significantly over time. Other contributing factors include dark skin pigmentation, which reduces UV absorption, and certain medical conditions that affect fat absorption, as vitamin D is a fat-soluble vitamin.

Comparison of Mild vs. Severe Vitamin D Deficiency Symptoms


Symptom Category	Mild Deficiency	Severe Deficiency
Physical	Occasional fatigue, general aches, or discomfort	Chronic exhaustion, intense bone pain, significant muscle weakness, and cramps
Skeletal	May experience some aches, particularly in the back	Increased risk of fractures, osteomalacia (adults), rickets (children)
Neuromuscular	Vague muscle weakness or soreness	Waddling gait, muscle twitching, tremors, or spasms
Mental Health	Subtler mood changes, feeling a bit "down"	More pronounced depression, anxiety, and impaired cognitive function
Immune System	Tendency to get sick more often than usual	Frequent, lingering respiratory infections and compromised immunity

Steps to Address Low Vitamin D Levels

If you suspect you have a vitamin D deficiency, a simple blood test can confirm it. A healthcare provider can recommend an appropriate course of action, which typically involves a combination of the following strategies:

Increase Sun Exposure: Spending a limited, safe amount of time in the sun can boost your body's natural vitamin D production. However, this must be balanced with sun safety, including sunscreen, which blocks UVB rays and thus inhibits synthesis.
Dietary Intake: Include more vitamin D-rich foods in your diet. Excellent sources include fatty fish (salmon, tuna, mackerel), fortified milk and cereals, and egg yolks.
Supplementation: Vitamin D supplements are a reliable way to ensure adequate intake, especially for those with limited sun exposure or specific health conditions. Supplements are available in two forms, D2 and D3, with D3 generally considered more effective at raising blood levels.

Conclusion

Understanding how your body feels when you're low on vitamin D is the first step toward correcting the issue and improving your overall health. From persistent fatigue and aching joints to a low mood and frequent colds, the symptoms can often be vague and mistakenly attributed to other causes. By recognizing these signs and working with a healthcare professional, you can take proactive steps to raise your vitamin D levels through diet, sunlight, and supplements, thereby supporting bone health, bolstering your immune system, and enhancing your mental well-being.

For more in-depth information on vitamin D's effects on the body, refer to health resources such as the National Institutes of Health.(https://www.ncbi.nlm.nih.gov/books/NBK532266/)

Frequently Asked Questions

A doctor can diagnose vitamin D deficiency with a simple blood test that measures the level of 25-hydroxyvitamin D in your body. The normal range for this test can vary, but most experts agree that a level below 20 ng/mL indicates a deficiency.

The best dietary sources of vitamin D include fatty fish like salmon and tuna, cod liver oil, egg yolks, beef liver, and fortified foods such as milk, cereals, and some orange juices.

Sunlight exposure is a primary source of vitamin D, but it's often not enough on its own. Factors like season, latitude, skin pigmentation, and sunscreen use can limit production. Many people, especially in certain climates, will need dietary sources or supplements to maintain adequate levels.

Individuals at a higher risk include breastfed infants, older adults, people with darker skin, those with limited sun exposure, people with malabsorption issues (like Crohn's disease), and individuals with obesity.

Untreated deficiency can lead to serious long-term health issues, including osteoporosis and fractures in adults, rickets in children, muscle weakness, and an increased risk of chronic diseases like autoimmune disorders and cardiovascular disease.

While natural methods take time, combining moderate sun exposure with dietary changes and, most effectively, high-quality supplements under a doctor's guidance is the best way to raise your levels. A healthcare provider can recommend a dosage appropriate for your specific needs.

There are two main forms of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). D3 is the form naturally produced by the skin when exposed to sunlight and is generally considered more effective at raising and maintaining blood levels.