How does low vitamin D and B12 make you feel? Understanding the Impact of Deficiency

October 9, 2025 •

3 min read

According to Cleveland Clinic, vitamin deficiencies are common worldwide, with vitamin D and B12 among the most prevalent. So, how does low vitamin D and B12 make you feel? The effects can range from persistent fatigue and mood disturbances to more serious neurological issues, significantly impacting daily life.

Quick Summary

Insufficient vitamin D can lead to bone pain, muscle weakness, and mood changes, while low B12 can cause severe fatigue, nerve damage, and cognitive issues due to poor red blood cell production and nerve function.

Key Points

Shared Symptoms: Both low vitamin D and B12 can cause significant fatigue and mood changes, often making them difficult to differentiate without testing.
Distinct Neurological Impact: B12 deficiency is known for specific neurological symptoms like 'pins and needles' (paresthesia), poor balance, and cognitive issues, unlike Vitamin D deficiency.
Bone Health vs. Nerve Health: While low vitamin D primarily impacts bone health, leading to pain and weakness, low B12 directly affects nerve function and red blood cell production.
Multiple Causes: Deficiencies can result from dietary choices (especially veganism for B12), malabsorption disorders (like Crohn's), lack of sun exposure (for Vitamin D), and age.
Diagnosis is Key: Blood tests are necessary to accurately diagnose a deficiency in either vitamin and to determine the most appropriate course of treatment.
Treatments Vary: Treatment can range from oral supplements to injections for B12, depending on the severity and cause, with regular monitoring often required.

The Essential Roles of Vitamin D and Vitamin B12

To understand how does low vitamin D and B12 make you feel, it's crucial to first recognize the vital roles these micronutrients play in the body. Vitamin D is primarily known for its role in bone health by aiding calcium and phosphorus absorption, but it also supports immune function, cell growth, and mood regulation. A deficiency can impact musculoskeletal and mental health.

Vitamin B12 is essential for neurological health and red blood cell formation. It's involved in DNA synthesis and nerve function, affecting every cell. Deficiency impairs nerve function and oxygen transport, causing symptoms that can develop gradually.

Specific Symptoms of Vitamin D Deficiency

A lack of vitamin D may have subtle early symptoms that worsen over time. Common signs include fatigue, bone and muscle pain, mood changes, impaired wound healing, frequent infections, and potentially hair loss.

Specific Symptoms of Vitamin B12 Deficiency

B12 deficiency affects nerve function and red blood cells, leading to distinct symptoms. These include extreme fatigue, pins and needles sensation, cognitive impairment, psychological problems like irritability and confusion, a sore tongue (glossitis), and balance problems.

Distinguishing Between Vitamin D and B12 Deficiency Symptoms

While some symptoms overlap, certain signs help differentiate these deficiencies. Blood tests are essential for confirmation.


Symptom	Vitamin D Deficiency	Vitamin B12 Deficiency
Fatigue	Mild to moderate.	Severe and debilitating.
Pain	Bone and muscle pain.	Tingling, numbness, nerve pain.
Mood	Depressed mood.	Irritability, confusion, severe depression.
Neurological	General muscle weakness.	Paresthesia, poor balance, cognitive decline.
Physical Appearance	None specific.	Pale/yellowish skin, sore red tongue.
Other	Weakened bones, hair loss.	GI issues, appetite loss.

Causes and Risk Factors

Deficiencies stem from various factors, from diet to medical conditions. Lack of sunlight, poor diet, and malabsorption can cause low vitamin D. Causes of low B12 include pernicious anemia, vegan/vegetarian diets, gastric surgery, age, and certain medications.

Diagnosis and Treatment Options

Consult a healthcare provider if deficiency is suspected. Diagnosis involves reviewing symptoms and blood tests for vitamin D (25-hydroxyvitamin D) and B12 levels. Treatment includes diet, sun exposure, and supplements for vitamin D. For B12, treatment depends on the cause and may involve injections or oral supplements. Dietary changes are also important for both.

Prevention Strategies

Prevention is crucial and often involves lifestyle and diet changes. Maintaining a balanced diet rich in sources of both vitamins, getting moderate sun exposure (for vitamin D), and considering supplementation if needed are key strategies. Regular check-ups and blood tests are also beneficial, especially for high-risk individuals. Responsible supplementation should be discussed with a doctor.

Conclusion

Low vitamin D and B12 can significantly impact how you feel, causing fatigue, mood changes, and specific neurological or musculoskeletal issues. While fatigue and low mood are shared, bone pain points to low vitamin D, and tingling to low B12. Diagnosis is made through blood tests, and treatment with injections, supplements, and diet changes is effective. Promptly addressing deficiencies prevents long-term complications and improves well-being.

For more information on the specific roles of B vitamins in nerve health, a resource from {Link: Neurobion https://www.neurobion.com/en-ph/nerve-health/b-vitamins/b1-b6-b12-vitamins-for-healthy-nervous-system} can provide further detail.

Frequently Asked Questions

Yes, deficiencies in both vitamins have been linked to mood changes, including feelings of depression and irritability. Vitamin D is important for brain function, while B12 influences neurotransmitter synthesis, both of which can impact mental health.

Vitamin D can be found in fortified foods like milk and cereals, as well as fatty fish (salmon, tuna) and eggs. B12 is primarily found in animal products such as meat, fish, dairy, and eggs. Fortified cereals and nutritional yeast are options for those on plant-based diets.

Both are typically diagnosed through a simple blood test. For vitamin D, a 25-hydroxy vitamin D test measures levels. For B12, blood levels are checked, and sometimes additional tests for metabolic byproducts are ordered, especially if levels are borderline.

Yes, it is possible and not uncommon to have both deficiencies simultaneously, particularly in older adults, individuals with malabsorption disorders, or those with restricted diets.

Supplements can effectively treat and reverse deficiencies, but the effectiveness depends on the underlying cause. In cases of malabsorption, such as pernicious anemia, B12 injections may be necessary, and lifelong supplementation could be required.

Neurological symptoms of B12 deficiency can include tingling or numbness in the hands and feet (paresthesia), balance problems, cognitive issues like memory loss or confusion, and even changes in mood and behavior.

Improvement varies depending on the severity and duration of the deficiency. Symptoms like fatigue may improve within weeks of starting treatment, but nerve damage and more serious neurological issues can take longer to resolve and may sometimes be irreversible.