General physical symptoms of vitamin B12 deficiency can include: Feeling very tired or weak. Experiencing nausea, vomiting or diarrhea. Not feeling as hungry as usual. Weight loss. Having a sore mouth or tongue. Having yellowish skin. Neurological symptoms of vitamin B12 deficiency can include: Numbness or tingling in your hands and feet Vitamin deficiency can cause a number of symptoms, including fatigue, dry skin and hair, depression, poor wound healing, and more. While they can vary between deficiencies, many of them overlap. Usually, noticeable effects don't begin to develop until you've had low levels for several months. bone loss depression type 2 diabetes heart disease multiple sclerosis An estimated 1 billion people around the globe have low blood levels of the vitamin ( 4 ). One research review found that 1. Fatigue, bone pain, muscle weakness Feeling tired? Experiencing bone pain? Having muscle weakness? It could be a sign that you're lacking vitamin D.  This vitamin is important for bone health along with the health of your nervous, musculoskeletal and immune systems. Older adults are at higher risk for being D deficient. 67pgK.