The constant weakness and nausea may be the early pregnancy reaction of women during pregnancy, or it may be the symptomatic manifestation of certain diseases, such as acute gastroenteritis, hypoglycemia, diabetic ketoacidosis, etc., which should be consulted in time to find out the cause of the disease. 1. Early pregnancy reaction: due to the rise in hormone levels, women in early pregnancy can appear a series of early pregnancy reaction, including nausea, fatigue, can also be accompanied by vomiting, drowsiness, anorexia greasy food, etc. These reactions usually in about 12 weeks of pregnancy can disappear naturally. 2. Acute gastroenteritis: due to acute inflammation of the gastrointestinal mucosa caused by viral and bacterial infections, patients may experience nausea and vomiting, accompanied by abdominal pain and diarrhea, which can lead to fatigue, dehydration and electrolyte disorders, and even cause shock and other symptoms due to frequent vomiting. 3. Hypoglycemia: Hypoglycemia is a disease caused by the reduction of plasma glucose due to various factors such as drugs, nutritional deficiencies and heredity. Patients often manifest nausea, fatigue, sweating, tremor, etc., and in severe cases, mental changes can also occur. 4. Diabetic ketoacidosis: due to the metabolic disorder syndrome caused by insufficient insulin secretion and too much antagonistic insulin, patients mainly manifested as polydrinking, polyphagia, polyuria and malaise, etc. With the development of the disease, fatigue, nausea and vomiting, loss of appetite, breath smell of rotten apples and other manifestations, and different degrees of impaired consciousness in the late stage can also occur. When patients have symptoms such as fatigue and nausea all the time, it is recommended to consult a doctor in time, improve relevant examinations, clarify the cause of the disease and carry out relevant treatment.