Diabetes mellitus (DM), commonly referred to as diabetes, is a group of metabolic disorders in which there are high blood sugar levels over a prolonged period.[10] Symptoms of high blood sugar include frequent urination, increased thirst, and increased hunger.[2] If left untreated, diabetes can cause many complications.[2] Acute complications can include diabetic ketoacidosis, hyperosmolar hyperglycemic state, or death.[3] Serious long-term complications include cardiovascular disease, stroke, chronic kidney disease, foot ulcers, and damage to the eyes.[2]
Jump up ^ Haw JS, Galaviz KI, Straus AN, Kowalski AJ, Magee MJ, Weber MB, Wei J, Narayan KM, Ali MK (December 2017). "Long-term Sustainability of Diabetes Prevention Approaches: A Systematic Review and Meta-analysis of Randomized Clinical Trials". JAMA Internal Medicine. 177 (12): 1808–1817. doi:10.1001/jamainternmed.2017.6040. PMC 5820728. PMID 29114778.
Retinopathy: If blood sugar levels are too high, they can damage the eyes and cause vision loss and blindness. Retinopathy causes the development and leaking of new blood vessels behind the eye. Other effects of diabetes, such as high blood pressure and high cholesterol, can make this worse. According to the CDC, early treatment can prevent or reduce the risk of blindness in an estimated 90 percent of people with diabetes.
Before you find yourself shocked by a diabetes diagnosis, make sure you know these 20 diabetes signs you shouldn’t ignore. If you identify with any of these warning signs on the list, be sure to visit your doctor ASAP to get your blood sugar tested. And if you want to reduce your risk of becoming diabetic in the first place, start with the 40 Tips That Double Weight Loss!
Diabetes mellitus is not a single disorder but a heterogeneous group of disorders. All forms are characterized by hyperglycemia and disturbances of carbohydrate, fat, and protein metabolism which are associated with absolute or relative deficiencies of insulin action and/or insulin secretion. The World Health Organization (WHO) developed a now widely accepted classification of the disorder, largely based on clinical characteristics (see Table 1, WHO, 1985).

Hemoglobin A1c or HbA1c is a protein on the surface of red blood cells. The HbA1c test is used to monitor blood sugar levels in people with type 1 and type 2 diabetes over time. Normal HbA1c levels are 6% or less. HbA1c levels can be affected by insulin use, fasting, glucose intake (oral or IV), or a combination of these and other factors. High hemoglobin A1c levels in the blood increases the risk of microvascular complications, for example, diabetic neuropathy, eye, and kidney disease.
According to the Mayo Clinic, doctors may use other tests to diagnose diabetes. For example, they may conduct a fasting blood glucose test, which is a blood glucose test done after a night of fasting. While a fasting blood sugar level of less than 100 milligrams per deciliter (mg/dL) is normal, one that is between 100 to 125 mg/dL signals prediabetes, and a reading that reaches 126 mg/dL on two separate occasions means you have diabetes.
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