Diabetes mellitus is a group of diseases characterized by elevated blood glucose. Persistent hyperglycemia and long-term metabolic disorders can lead to damage to tissues and organs throughout the body, especially the eyes, kidneys, cardiovascular and nervous systems, as well as their dysfunction and failure, but there are not always obvious clinical manifestations in the early stages. In the early stages of diabetes, elevated blood glucose is often found during physical examination and may have no clinical symptoms at all, but there are no specific indicators of how high blood glucose begins to show symptoms, and each patient has a great deal of specificity. Typical symptoms: It is also often referred to as the three symptoms of polyhydramnios, polyuria, polyphagia and lethargy. Most of them are caused by increased osmolarity due to high blood glucose in the blood, which causes thirst for water. Atypical symptoms: Some patients with type 2 diabetes have atypical symptoms, only dizziness and weakness, or even no symptoms. In some cases, early onset or pre-onset stage of diabetes, hypoglycemic symptoms may appear before lunch or dinner. The common feature is that there is no characteristic, and patients usually visit the doctor with other symptoms and find the abnormality of blood sugar by chance. Acute complications: Generally, high osmotic pressure is caused by the rapid increase of blood glucose under the stressful condition, followed by corresponding effects on different organs, which may include loss of appetite, nausea, vomiting, abdominal pain, aggravation of polyuria, dizziness, drowsiness, blurred vision, respiratory difficulty, coma, etc. Chronic complications: generally only appear in patients with long-term hyperglycemia, mainly focusing on other systems of heart, brain, kidney, eye, foot and nerve damage, but also in patients who come to the first consultation due to complications because the primary symptoms are not obvious. Commonly, diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, recurrent infections, diabetic foot, and pruritus of the skin. Therefore, the organs damaged by diabetes are very extensive, and the clinical manifestations vary at different stages, so it is generally difficult to rely on symptoms alone for early detection, and regular blood glucose checks are the key to early diagnosis and prevention of diabetes