Common signs of nutritional deficiencies vary based on which nutrient is lacking but can include symptoms such as fatigue, muscle weakness, hair loss, and compromised immune function. For example, a deficiency in iron may cause anemia, leading to fatigue and weakness, while insufficient vitamin D can result in bone pain or muscle weakness. Skin issues might indicate a lack of essential fatty acids or vitamin E. Being aware of these signs helps individuals address potential deficiencies through diet or supplementation.