Feeling weak all the time can be seen in the following conditions: i. Colds, viral infections that invade the muscles can cause symptoms such as weakness of the limbs. Leukopenia, often caused by viral infections or reduced activity, other conditions are rare, such as leukemia, poisoning, etc. Viral infections can lead to leukopenia causing weakness, and reduced activity can lead to leukocyte wall attachment in the blood vessels, resulting in a decrease in the number of leukocytes flowing in the blood vessels and causing weakness. Anemia is caused by a decrease in the ability of red blood cells to carry oxygen due to a decrease in hemoglobin, resulting in a lack of oxygen in the body and causing general weakness. Hypothyroidism, due to the lack of thyroxine causes low metabolic state, weakness, reluctance to move, dry stools, slow heart rate, etc. Poor sleep, due to poor sleep, the body does not get enough rest will appear weakness. Sixth, other causes such as leukemia, tumors, etc.