The causes of old people’s lack of energy and fatigue may be malnutrition, cardiovascular diseases such as cardiac insufficiency and low blood pressure, endocrine system diseases such as hypothyroidism, etc., which need to be analyzed specifically. 1. malnutrition: the elderly due to reduced food intake, gastrointestinal digestion and absorption function is weakened and other reasons are prone to malnutrition, which can be manifested as hypoglycemia, anemia, hypoproteinemia, and so on, there will be a lack of energy and fatigue of the performance of the body, blood routine, biochemistry and other tests can assist in the definitive diagnosis. 2. cardiovascular diseases: cardiovascular diseases such as cardiac insufficiency, hypotension, etc., due to insufficient perfusion of organs and tissues may appear weak and tired, blood pressure measurement, cardiac ultrasound and other tests can assist in making a clear diagnosis. 3. Endocrine system diseases: endocrine system diseases such as hypothyroidism, due to the decline in the level of thyroid hormone or resistance, the body’s metabolic rate decline, thus appearing weak and fatigue, thyroid function and ultrasound and other tests can assist in the definitive diagnosis. Thyroid function and ultrasound tests can help to clarify the diagnosis. It is recommended to consult a doctor in time for a clear diagnosis and early treatment to avoid delaying the condition.