Weakness in an 80 year old man on dialysis needs to be identified and treated for the cause. Common causes include malnutrition, electrolyte disorders, hypotension and so on. 1. Malnutrition: During dialysis, the energy consumption of the human body is large, and some patients will also suffer from loss of water-soluble vitamins, which will lead to weakness. After dialysis, some protein-rich foods can be taken in, such as lean meat, milk and fish, etc., and the weakness can be reduced through dietary adjustment. 2. Electrolyte disorders: Hypokalemia may result in weakness after dialysis, so the patient’s blood potassium level can be monitored and appropriate amount of potassium can be added to improve the symptoms of weakness. 3. Hypotension: if too much water is removed in the process of dialysis, it may lead to hypotension, and the patient may have the symptom of weakness, so the patient can be infused with saline, and human albumin can be used if necessary. When the 80-year-old dialysis weakness may also have other reasons, it is recommended that patients go to the regular hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.