Vitamin deficiency occurs when the body does not get enough vitamins, which are essential nutrients needed for various bodily functions. This can happen due to poor diet, certain medical conditions, or absorption issues. Common vitamins that people may lack include vitamin C, vitamin D, and vitamin B12. Symptoms of vitamin deficiency can vary widely, including fatigue, weakened immunity, and skin problems. If left untreated, these deficiencies can lead to more serious health issues, such as scurvy from lack of vitamin C or rickets from insufficient vitamin D. A balanced diet is crucial for preventing these deficiencies.