Lethargy is a state of extreme tiredness, low energy, and lack of motivation that can affect daily life. It may be caused by lifestyle factors such as poor sleep, stress, or unhealthy diet, as well as medical conditions like anemia, thyroid problems, infections, or chronic fatigue syndrome. Learn about the common causes, symptoms, and treatment options for lethargy, along with practical tips for boosting energy levels, improving sleep quality, and knowing when to seek medical advice.