Nausea and weakness are usually caused by brain diseases, mental factors or digestive system: 1. Brain diseases, cerebral arteriosclerosis or brain tumors can lead to insufficient blood supply to the brain, resulting in nausea and weakness. Patients with hypertension are also prone to dizziness, nausea, vomiting and weakness when their blood pressure rises, especially in the early morning. 2. Mental factors, long-term tension, anxiety or mood changes easily stimulate the cerebral cortex causing neurological disorders. This phenomenon can also occur when you read books, watch TV, or play with your cell phone for a long time, resulting in excessive brain use. 3, digestive system diseases, suffering from acute and chronic gastroenteritis, gastric ulcer, duodenal ulcer, pyloric obstruction and other diseases, the spleen and stomach digestive function is reduced, there will be abdominal pain, nausea, belching, vomiting and other symptoms, usually recurring, easily leading to physical wasting and weakness.