There are many clinical causes that can cause dry mouth and generalized weakness, and the common ones are as follows: 1. Diabetes mellitus: Patients have symptoms of dry mouth accompanied by generalized weakness. If diabetes mellitus occurs, the symptoms of three more and one less may be seen, i.e., symptoms of drinking more, urinating more, eating more and losing weight, or there may be no symptoms of three more and one less, so it is necessary to do blood glucose testing to help diagnose whether dry mouth and generalized weakness are caused by increased blood glucose; 2. 3. Hyperparathyroidism: The lack of AVP (arginine pressor) in the body causes urine to be discharged continuously, resulting in dry mouth and general weakness; 4. Hyperthyroidism: Dry mouth and general weakness, which may be accompanied by irritability, panic, hand trembling, hunger and excessive sweating. Patients can have blood tests for three thyroid functions to help detect the presence of hyperthyroidism.