Bone pain and muscle weakness: Vitamin D is essential for maintaining healthy bones, and a deficiency can cause bone pain, muscle weakness, and an increased risk of fractures.br br Fatigue: Vitamin D plays a role in energy metabolism, and a deficiency can cause fatigue and a lack of energy.br br Mood changes: Vitamin D receptors are present in the brain, and a deficiency has been linked to an increased risk of depression and other mood disorders.br br Impaired immune function: Vitamin D plays a crucial role in maintaining a healthy immune system, and a deficiency can increase the risk of infections and autoimmune diseases.br br Delayed wound healing: Vitamin D is involved in the process of wound healing, and a deficiency can impair this process.br br Hair loss: While rare, severe vitamin D deficiency can cause hair loss.br vitamin d deficiency complications?br Vitamin D deficiency can lead to several complications, particularly if it is left untreated. Some of the potential complications of vitamin D deficiency include:br br Osteomalacia and rickets: Vitamin D is essential for healthy bone development, and a deficiency can cause softening of the bones (osteomalacia) in adults and rickets in children.