What Happens If You Don't Have Enough Vitamin D2?

November 24, 2025 •

4 min read

According to the NIH, almost one in four people in the United States have inadequate vitamin D blood levels, highlighting a widespread nutritional issue. If you don't have enough vitamin D2, your body can experience a range of negative health consequences that affect more than just your bones.

Quick Summary

A lack of vitamin D2 can lead to serious health problems, including weakened bones, impaired immune function, and mood changes. A deficiency occurs when the body lacks sufficient ergocalciferol from food sources to support crucial bodily processes like calcium absorption and immune system regulation.

Key Points

Weakened Bones: A lack of vitamin D2 can cause your body to pull calcium from your bones, leading to osteomalacia in adults and rickets in children.
Muscle Weakness: Deficiency can lead to muscle pain and weakness, which may increase the risk of falls, especially in older adults.
Impaired Immunity: Vitamin D is vital for immune function, so inadequate levels can result in frequent infections and a slower recovery from illness.
Increased Fracture Risk: Weakened bones from prolonged deficiency are more susceptible to fractures and osteoporosis.
Mood Disorders: Low vitamin D levels have been linked to mood changes, including depression.
Common Symptoms: Watch for subtle signs like fatigue, bone pain, and muscle weakness, which can be indicators of a deficiency.
Plant-Based Source: Vitamin D2 (ergocalciferol) comes from plant sources like UV-treated mushrooms and fortified foods, distinguishing it from D3.

The Crucial Role of Vitamin D and What Vitamin D2 Is

Vitamin D is a fat-soluble nutrient that is essential for several key bodily functions, most famously for regulating calcium and phosphate levels to maintain strong bones. However, its role extends to supporting the immune system, modulating cell growth, and influencing mood. There are two main forms of this vitamin: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is primarily found in plant sources, such as mushrooms treated with UV light and fortified foods like cereals and plant-based milks. D3 is produced by the skin upon sun exposure and is also found in animal products like fatty fish and egg yolks. While both forms serve the same function, some research suggests D3 is more effective at raising and maintaining vitamin D levels in the blood. Understanding what happens when you don't have enough vitamin D2, or any form of vitamin D, is critical for your overall health.

Serious Health Consequences of Vitamin D2 Deficiency

When your body lacks sufficient vitamin D2, a cascade of health issues can occur. The most prominent consequences relate to bone health. Without enough vitamin D, the body cannot absorb calcium and phosphorus properly. To compensate, the body pulls calcium from its own bones, leading to a loss of bone density. In adults, this can result in osteomalacia, a painful condition characterized by weak, soft bones. In children, a severe deficiency can cause rickets, a rare disease that leads to bone deformities and improper growth. The weakened bones also increase the risk of fractures, especially in older adults.

Beyond bone health, a lack of vitamin D2 can affect other systems. The immune system requires adequate vitamin D to function correctly and fight off infections. A deficiency may therefore lead to a higher frequency of illnesses and slower wound healing. Furthermore, research has linked low vitamin D levels to an increased risk of chronic conditions, including cardiovascular disease and autoimmune disorders.

Recognizing the Subtle and Severe Symptoms

The symptoms of a vitamin D deficiency can be subtle at first and often go unnoticed. For adults, common signs include fatigue, muscle weakness and pain, and bone pain, particularly in the lower back. Individuals might also experience mood changes, such as depression. As the deficiency becomes more severe or chronic, symptoms become more pronounced. In children, signs may be more visible and include muscle weakness, bone pain, and skeletal deformities.

Common Symptoms of Vitamin D Deficiency

Chronic Fatigue: Persistent tiredness that doesn't improve with rest.
Bone and Joint Pain: Aches, especially in the back, that can sometimes be misdiagnosed as other conditions like arthritis.
Muscle Weakness and Aches: Often felt in the proximal muscles and can increase the risk of falls, particularly in the elderly.
Mood Changes: Low vitamin D has been associated with an increased risk of depression.
Impaired Wound Healing: Vitamin D is important for immune function, which plays a role in skin repair.
Frequent Infections: A weakened immune system can make one more susceptible to frequent illnesses.

Comparison of Vitamin D2 vs. D3

While this article focuses on D2, it is important to understand how it compares to D3. Both are crucial for health, but they differ in their origin and efficacy.


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Source	Plant-based sources like UV-exposed mushrooms, yeast, and fortified foods (e.g., some cereals and plant-based milks).	Primarily from animal products (fatty fish, fish liver oil, eggs) and produced in the skin upon sun exposure.
Availability	Can be found in supplements and is often used in fortified foods. Prescription-strength D2 is also available.	Widely available in over-the-counter supplements and is generally considered more bioavailable.
Effectiveness	Studies suggest it may be less effective at raising and maintaining blood vitamin D levels over time compared to D3.	Often more effective at increasing and sustaining overall vitamin D levels in the blood.
Absorption	Well-absorbed in the gut, but its utilization by the body can be less efficient than D3.	More efficiently utilized by the body, leading to more consistent blood levels.

How to Prevent and Treat a Deficiency

Preventing a vitamin D2 deficiency involves a combination of dietary adjustments and supplementation. Since D2 is found in plants and fortified foods, those on vegan or vegetarian diets should pay particular attention to their intake. Incorporating UV-treated mushrooms, fortified plant-based milks, and cereals can help. For those with diagnosed deficiencies, a healthcare provider might recommend high-dose supplementation with either D2 or D3 for a specified period, followed by a lower maintenance dose. Regular monitoring via a blood test is the most reliable way to track vitamin D status.

Another important aspect of managing vitamin D levels is sunlight exposure, which primarily helps the body produce D3. While not a direct source of D2, healthy sun exposure is essential for overall vitamin D status. However, skin cancer risks must be considered, and individuals with darker skin tones or those who spend most of their time indoors are less efficient at producing vitamin D from sunlight. In these cases, dietary intake and supplementation become even more crucial.

Conclusion

Ignoring a vitamin D2 deficiency can have profound and lasting effects on your health, from debilitating bone pain and weakness to impaired immune function and an increased risk of chronic diseases. Given the prevalence of inadequate vitamin D levels worldwide, proactive management is key. By paying attention to dietary sources like UV-treated mushrooms and fortified foods, and discussing supplementation with a healthcare provider, individuals can ensure they receive the necessary amounts. Regular check-ups can help monitor vitamin D levels and address any deficiencies early, safeguarding bone health, supporting immune function, and promoting overall well-being. By understanding the consequences of insufficient vitamin D2, you can take informed steps to protect your health.

Visit the NIH's Office of Dietary Supplements for more information on vitamin D

Frequently Asked Questions

The primary function of vitamin D2, like all forms of vitamin D, is to help the body absorb calcium and phosphorus from the gut. This process is crucial for the development and maintenance of strong, healthy bones.

Early signs of a vitamin D2 deficiency can be subtle and may include fatigue, general tiredness, muscle weakness, and bone or joint pain. In adults, these symptoms are often less obvious than in children.

Not having enough vitamin D2 can lead to weakened bones (osteomalacia in adults and rickets in children), an increased risk of fractures, impaired immune function, and a higher susceptibility to chronic diseases like cardiovascular disease.

You can increase your vitamin D2 intake by consuming plant-based foods rich in this vitamin, such as UV-treated mushrooms. It is also found in many fortified foods, including some plant-based milks and breakfast cereals.

A vitamin D deficiency is typically diagnosed through a blood test that measures the level of 25-hydroxyvitamin D in your serum. A healthcare provider will also perform a clinical assessment and review your symptoms and risk factors.

No, you cannot get vitamin D2 from sun exposure. The body produces vitamin D3 (cholecalciferol) when exposed to sunlight. Vitamin D2 (ergocalciferol) comes exclusively from dietary sources.

While both vitamin D2 and D3 can effectively increase blood vitamin D levels, research suggests that vitamin D3 is more potent and may be more effective at sustaining higher levels over a longer period.