Thiamine deficiency occurs when the body does not get enough thiamine, also known as vitamin B1. This vitamin is essential for converting carbohydrates into energy and is crucial for the proper functioning of the nervous system. A lack of thiamine can lead to various health issues, including beriberi, which affects the cardiovascular and nervous systems, and Wernicke-Korsakoff syndrome, a serious brain disorder often associated with chronic alcohol consumption. Symptoms of thiamine deficiency may include fatigue, irritability, confusion, and muscle weakness. It can be caused by inadequate dietary intake, certain medical conditions, or excessive alcohol consumption. Treatment typically involves dietary changes and thiamine supplementation to restore healthy levels in the body.