Feeling weak and tired may be caused by excessive exercise, lack of sleep and other physiological factors, but also due to acute hypertension, anemia, cerebral infarction and other causes. 1. Acute hypertension: Acute hypertension will enhance the tensile ability of blood vessels, causing an increase in intracranial blood pressure, which will lead to neurological dysfunction, and clinically manifest as a lack of energy and fatigue. 2. Anemia: Anemia is mainly caused by insufficient hemoglobin in the blood, which results in the weakening of hemoglobin oxygen capacity and insufficient supply of oxygen to the organs, and is often manifested as dizziness, lack of energy and fatigue in the clinic. 3. Cerebral infarction: cerebral infarction will cause localized death of brain tissues and abnormal function, which will lead to abnormal conduction function of the nervous system and loss of muscle regulation ability, and there will be fatigue and tiredness. In addition, some physiological factors, such as excessive exercise and lack of sleep, can also have the symptom of feeling weak and tired. Excluding physiological factors, if the symptoms recur, it is recommended to go to the hospital for examination, the doctor will give a corresponding diagnosis based on clinical symptoms, clear causes and timely treatment.