What Happens if You Have Low Vitamin D?

December 1, 2025 •

3 min read

According to the National Institutes of Health, nearly one in four people in the United States has vitamin D levels considered too low or inadequate for bone and overall health. This widespread issue, known as vitamin D deficiency, can lead to a surprising array of health problems that many people don't recognize as related to this 'sunshine vitamin'.

Quick Summary

This article explores the consequences of low vitamin D levels, detailing the wide range of symptoms and significant health risks, from impaired bone health and muscle weakness to increased risk of chronic conditions like autoimmune disorders and cardiovascular disease.

Key Points

Bone Weakening: Low vitamin D impairs calcium absorption, leading to weak, soft, or brittle bones and increasing fracture risk.
Chronic Fatigue: Persistent tiredness and fatigue are common signs of a vitamin D deficiency.
Muscle Issues: Insufficient vitamin D can cause muscle aches, weakness, and cramps.
Impaired Immunity: The vitamin is crucial for immune function, and low levels can lead to more frequent infections.
Increased Risk of Falls: In older adults, low vitamin D contributes to muscle weakness and a higher risk of falling.
Systemic Inflammation: Chronic deficiency is linked to higher inflammatory markers and an increased risk of autoimmune diseases.
Mental Health: Links have been found between low vitamin D levels and an increased risk of anxiety and depression.
Treatment is Effective: Deficiency is treatable with supplements, dietary changes, and proper sun exposure under medical guidance.

The Importance of Vitamin D in the Body

Vitamin D is a fat-soluble nutrient essential for regulating calcium and phosphate, crucial minerals for strong bones, teeth, and muscles. Without enough vitamin D, the body struggles to absorb calcium from food, leading it to take calcium from the bones, weakening them over time. Beyond bone health, it supports immune, muscle, and cellular functions.

Immediate and Chronic Symptoms of Low Vitamin D

Symptoms of low vitamin D can vary greatly. Some people might have no noticeable signs, while others experience a range of issues, from mild to severe. Chronic or severe deficiency can lead to more serious effects.

Common Manifestations of Deficiency

Fatigue: Feeling persistently tired.
Bone and Back Pain: Often occurs due to impaired calcium absorption.
Muscle Weakness, Aches, or Cramps: Vitamin D is important for muscle function.
Frequent Illness: Linked to a weakened immune response.
Mood Changes: Potential association with depression.
Impaired Wound Healing: May slow recovery.
Hair Loss: Can be related to autoimmune conditions linked to deficiency.

Severe Health Complications for Adults and Children

Untreated low vitamin D can lead to more serious health issues, with different conditions affecting children and adults.

Comparison of Deficiency Consequences


Condition	Affected Population	Primary Symptoms	Outcome	Risk Factors
Rickets	Children	Bowed legs, delayed walking, bone pain, muscle weakness	Permanent bone deformities if untreated	Lack of sun exposure, low vitamin D in breast milk
Osteomalacia	Adults	Chronic bone pain, muscle weakness, risk of fractures	Softening and weakening of bones	Inadequate sun exposure, malabsorption issues
Osteoporosis	Primarily older adults	Weakened bones, increased fracture risk	Fragile bones prone to breakage	Low vitamin D worsens the condition

Long-Term Systemic Health Risks

Research suggests that low vitamin D affects more than just bones, potentially increasing the risk of several other health issues.

Autoimmune and Inflammatory Conditions

Studies indicate a link between low vitamin D and a higher risk of autoimmune diseases like multiple sclerosis and rheumatoid arthritis. Deficiency is also associated with increased inflammatory markers.

Cardiovascular Disease

Some studies suggest a connection between low vitamin D and heart disease risk factors, including high blood pressure. Severe deficiency has been linked to worse outcomes in patients with acute coronary syndrome.

Mental Health Implications

Links have been observed between low vitamin D and conditions like anxiety and depression. The vitamin is thought to be important for brain function.

Increased Risk of Falls

In older adults, the muscle weakness and poor balance associated with severe vitamin D deficiency can increase the likelihood of falls, leading to potential injuries like hip fractures.

How to Address a Vitamin D Deficiency

If a deficiency is suspected, a blood test by a healthcare professional can confirm it. Treatment options typically include:

Sunlight: Skin exposure to sunlight allows the body to produce vitamin D. However, this method is influenced by many factors and carries skin cancer risks.
Diet: Foods like fatty fish, fish liver oils, egg yolks, and fortified products (milk, cereals) contain some vitamin D.
Supplements: Over-the-counter D2 and D3 supplements are common. Severe cases may require higher doses or injections prescribed by a doctor.

Conclusion

Low vitamin D is a widespread issue with significant health implications. It can cause bone problems like osteoporosis, muscle weakness, increased risk of falls, and may be linked to autoimmune conditions and cardiovascular disease. Identifying and treating a deficiency through supplements, diet, and safe sun exposure, guided by a healthcare provider, is crucial for preventing long-term health complications. Understanding what happens if you have low vitamin D allows for proactive management to protect overall health.

Additional Reading

The National Institutes of Health Office of Dietary Supplements offers a detailed fact sheet on vitamin D.(https://ods.od.nih.gov/factsheets/VitaminD-Consumer/)

Frequently Asked Questions

Some of the earliest signs can be vague, such as persistent fatigue, general muscle aches, and bone pain, especially in the lower back. Many people may not have any noticeable symptoms at all.

A healthcare professional can check your vitamin D levels with a simple blood test, which measures the amount of 25-hydroxyvitamin D in your blood.

Research has linked low vitamin D levels to an increased risk of mood disorders, including anxiety and depression, though the evidence is mixed and further studies are needed to understand the connection fully.

The fastest way is typically through dietary supplements, especially higher-dose options that a doctor may prescribe for a short period. Safe sun exposure and consuming fortified foods also help, but supplements are the most targeted approach.

While bone and back pain are common symptoms, they can be caused by many other conditions. However, vitamin D deficiency impairs calcium absorption, which is a direct cause of bone pain and weakness.

Those at highest risk include older adults, people with darker skin pigmentation, breastfed infants, individuals with limited sun exposure, and people with conditions that limit fat absorption.

Both are bone disorders caused by low vitamin D. Rickets affects children, whose bones are still growing, causing bowed or bent bones. Osteomalacia affects adults, causing soft and weakened bones.