Neck melanosis is not usually a precursor to diabetes and may be caused by physiologic factors or by disease factors such as acanthosis nigricans. Although neck melanosis is not a precursor of diabetes, diabetes may induce acanthosis nigricans leading to neck melanosis. Early diabetes may have no obvious clinical manifestations, and some patients may have symptoms such as excessive drinking, excessive eating, excessive urination, weight loss, etc., and usually do not show symptoms of neck melanosis. Therefore, neck melanosis is usually not a precursor of diabetes. The main physiologic factor that can cause neck melanosis is long-term exposure of the neck to ultraviolet light. In addition, acanthosis nigricans, a skin disease characterized by deepening of skin color and papillary thickening of the skin, can also cause neck melanosis. And, diabetic patients are often associated with insulin resistance, which may trigger the development of acanthosis nigricans. It is advisable to go to the hospital and ask the doctor to make a judgment after eliminating physiological factors and not to make a blind judgment on your own when you have a case of neck melanosis.