Vitamin D3 Deficiency: 6 Signs and Symptoms

Understanding Vitamin D3 and Vitamin D3 Deficiency

What is Vitamin D3?

Vitamin D3 is an essential nutrient that supports multiple body systems, including bones, muscles, and the immune system. Vitamin D3 deficiency occurs when blood levels are too low, which can lead to symptoms such as muscle weakness, bone pain, and increased risk of chronic diseases.

The prohormone group that includes vitamin D2 (calciferol) and vitamin D3 (cholecalciferol) acts to support and increase the effects of other hormones in the body. While vitamin D3 can be synthesized by the body with sunlight, it can also be obtained through diet and supplements.

Normal levels of vitamin D3 are between 10 ng/ml and 50 ng/ml, with optimal levels around 30 ng/ml in order to ensure necessary calcium absorption and bone mineralization.

Dietary Sources of Vitamin D3

Vitamin D3 can be found in fatty fish, liver, cheese, and eggs and is also added to the U.S. milk supply and many breakfast cereals.

Why Deficiency is Common

Even with dietary sources, due to limited sunlight levels and durations in winter months in northern regions, 25% to 50% of those tested in clinical settings are deficient in vitamin D3.

Vitamin D3 supplementation is recommended not only from November through April when sunlight intensity is lowest, but also year-round, because sunscreen use and indoor lifestyles limit natural vitamin D production. Vitamin D3 deficiency is particularly common in winter months and in individuals with limited sun exposure or higher risk factors.

Emerging research shows that maintaining optimal vitamin D3 levels supports immune function, cardiometabolic health, and may help slow cellular aging.

Signs and Symptoms of Vitamin D3 Deficiency

Vitamin D3 is necessary for normal functioning in many of the body’s systems. Deficiencies in vitamin D3 have been associated with several symptoms and conditions:

1. Fibromyalgia and Chronic Fatigue Disease

Generalized muscle pain and symptoms like bone pain and unexplained muscle weakness might be a sign of vitamin D3 deficiency. Often, these symptoms are mistaken for fibromyalgia and chronic fatigue disease, and both of these conditions have been shown to have a high correlation with D3 deficiency with up to 70% of sufferers testing low in D3.

2. Osteoporosis

In addition to generalized muscle and bone pain, actual demineralization of bone can occur when deficiencies in vitamin D3 interfere with proper calcium absorption. Bones can become brittle and fractures may occur, especially in older people.

3. Kidney Disease

Those with chronic kidney disease should be checked for low vitamin D3 levels, as studies show impaired renal activity results in decreased conversion to D3.

4. Cardiovascular Disease

Studies have shown a high correlation between higher risk of cardiovascular disease and vitamin D3 deficiencies. Anyone with cardiovascular disease should be tested to ensure they are at normal D3 levels.

Recent research suggests that vitamin D deficiency in childhood may increase the risk of developing cardiovascular disease later in life, emphasizing the importance of maintaining adequate levels from an early age.

5. Asthma

An increase in the symptoms of asthma are also associated with D3 deficiencies, especially in children. Asthma sufferers in the northern climates tend to suffer more symptoms during the winter months from cold, and potentially from the lower levels of D3 resulting from lower levels and duration of sunlight.

6. Cancer

Vitamin D3 offers protection against several types of cancer including colon, breast, ovarian and prostate cancers. Vitamin D3 inhibits tumor growth and the proliferation of cancer cells. Cancer rates have been shown to be 67% higher among those with low levels of vitamin D3.

Risk Factors for Vitamin D3 Deficiency

• Limited sun exposure due to geography, indoor lifestyles, or sunscreen use. Daily high-SPF sunscreen use has been linked to higher rates of vitamin D deficiency, so supplementation may be necessary for those with low sun exposure.
• Older age or chronic kidney disease reducing vitamin D conversion
• Darker skin pigmentation, obesity, or fat malabsorption disorders
• Certain chronic illnesses affecting the immune system, bone, or cardiovascular health

Maintaining Healthy Vitamin D3 Levels to Prevent Deficiency

Dietary Sources

Include fatty fish (salmon, mackerel), fortified dairy, eggs, and mushrooms.

Sunlight Exposure

Moderate sun exposure is important for natural vitamin D3 production, typically 10–20 minutes several times per week on face and arms.

Supplementation

Vitamin D3 supplements are generally more effective than D2 at raising blood levels, as D2 can lower D3 concentrations.

Vitamin D3 supplements may be necessary, particularly for individuals at risk or during winter months. Consult a healthcare provider for dosing based on blood tests.

Monitoring and Testing

Regular 25(OH)D blood tests can ensure optimal levels and help prevent deficiency-related conditions.

Vitamin D3 has long been known for its relationship with calcium absorption and bone health, and recent research confirms its broader impact on immune function, cardiometabolic health, and aging. Ensuring adequate levels is essential for overall wellness

Originally posted May 2016. Updated October 23, 2025.