Vitamin D deficiency occurs when the body does not get enough vitamin D, an essential nutrient that helps maintain healthy bones and supports the immune system. This deficiency can result from limited sun exposure, poor dietary intake, or certain medical conditions that affect absorption. Symptoms may include fatigue, bone pain, and muscle weakness. People at higher risk for vitamin D deficiency include those with darker skin, older adults, and individuals living in areas with little sunlight. To prevent deficiency, it is important to include sources of vitamin D in the diet, such as fatty fish, fortified foods, and supplements if necessary. Regular sun exposure can also help the body produce this vital vitamin.