Jump up ^ Rubino, F; Nathan, DM; Eckel, RH; Schauer, PR; Alberti, KG; Zimmet, PZ; Del Prato, S; Ji, L; Sadikot, SM; Herman, WH; Amiel, SA; Kaplan, LM; Taroncher-Oldenburg, G; Cummings, DE; Delegates of the 2nd Diabetes Surgery, Summit (June 2016). "Metabolic Surgery in the Treatment Algorithm for Type 2 Diabetes: A Joint Statement by International Diabetes Organizations". Diabetes Care. 39 (6): 861–77. doi:10.2337/dc16-0236. PMID 27222544.
The term "diabetes" or "to pass through" was first used in 230 BCE by the Greek Apollonius of Memphis. The disease was considered rare during the time of the Roman empire, with Galen commenting he had only seen two cases during his career. This is possibly due to the diet and lifestyle of the ancients, or because the clinical symptoms were observed during the advanced stage of the disease. Galen named the disease "diarrhea of the urine" (diarrhea urinosa).
While many experts believe that most type 1 genes have been identified, the situation with type 2 diabetes is much different. A recent study found that the known genetic links to type 2 probably account for only about 6 percent of the genetic predisposition for that form of diabetes. This could mean either that some of the genes discovered have a bigger effect than is currently believed or that "we are still missing 94 percent of the genes," says Atul Butte, MD, PhD, an assistant professor of pediatrics at Stanford University.
People with diabetes either don't make insulin or their body's cells no longer are able to use the insulin, leading to high blood sugars. By definition, diabetes is having a blood glucose level of greater than or equal to126 milligrams per deciliter (mg/dL) after an 8-hour fast (not eating anything), or by having a non-fasting glucose level greater than or equal to 200 mg/dL along with symptoms of diabetes, or a glucose level of greater than or equal to 200 mg/dL on a 2-hour glucose tolerance test, or an A1C greater than or equal to 6.5%. Unless the person is having obvious symptoms of diabetes or is in a diabetic crisis, the diagnosis must be confirmed with a repeat test.
When the glucose concentration in the blood remains high over time, the kidneys will reach a threshold of reabsorption, and glucose will be excreted in the urine (glycosuria). This increases the osmotic pressure of the urine and inhibits reabsorption of water by the kidney, resulting in increased urine production (polyuria) and increased fluid loss. Lost blood volume will be replaced osmotically from water held in body cells and other body compartments, causing dehydration and increased thirst (polydipsia).
Most cases of diabetes involve many genes, with each being a small contributor to an increased probability of becoming a type 2 diabetic. If one identical twin has diabetes, the chance of the other developing diabetes within his lifetime is greater than 90%, while the rate for nonidentical siblings is 25–50%. As of 2011, more than 36 genes had been found that contribute to the risk of type 2 diabetes. All of these genes together still only account for 10% of the total heritable component of the disease. The TCF7L2 allele, for example, increases the risk of developing diabetes by 1.5 times and is the greatest risk of the common genetic variants. Most of the genes linked to diabetes are involved in beta cell functions.
Learning about the disease and actively participating in the treatment is important, since complications are far less common and less severe in people who have well-managed blood sugar levels. The goal of treatment is an HbA1C level of 6.5%, but should not be lower than that, and may be set higher. Attention is also paid to other health problems that may accelerate the negative effects of diabetes. These include smoking, elevated cholesterol levels, obesity, high blood pressure, and lack of regular exercise. Specialized footwear is widely used to reduce the risk of ulceration, or re-ulceration, in at-risk diabetic feet. Evidence for the efficacy of this remains equivocal, however.
Type 2 diabetes can be prevented with lifestyle changes. People who are overweight and lose as little as 7 percent of their body weight and who increase physical activity (for example, walking 30 minutes per day) can decrease their risk of diabetes mellitus by more than 50%. Metformin and acarbose, drugs that are used to treat diabetes, may reduce the risk of diabetes in people with impaired glucose regulation.
Every cell in the human body needs energy in order to function. The body's primary energy source is glucose, a simple sugar resulting from the digestion of foods containing carbohydrates (sugars and starches). Glucose from the digested food circulates in the blood as a ready energy source for any cells that need it. Insulin is a hormone or chemical produced by cells in the pancreas, an organ located behind the stomach. Insulin bonds to a receptor site on the outside of cell and acts like a key to open a doorway into the cell through which glucose can enter. Some of the glucose can be converted to concentrated energy sources like glycogen or fatty acids and saved for later use. When there is not enough insulin produced or when the doorway no longer recognizes the insulin key, glucose stays in the blood rather entering the cells.
Diabetes mellitus has been recorded in all species but is most commonly seen in middle-aged to older, obese, female dogs. A familial predisposition has been suggested. It is possible to identify two types of diabetes, corresponding to the disease in humans, depending on the response to an intravenous glucose tolerance test. Type I is insulin-dependent and comparable to the juvenile onset form of the disease in children in which there is an absolute deficiency of insulin—there is a very low initial blood insulin level and a low response to the injected glucose. This form is seen in a number of dog breeds, particularly the Keeshond, Doberman pinscher, German shepherd dog, Poodle, Golden retriever and Labrador retriever.
Clear evidence suggests a genetic component in type 1 diabetes mellitus. Monozygotic twins have a 60% lifetime concordance for developing type 1 diabetes mellitus, although only 30% do so within 10 years after the first twin is diagnosed. In contrast, dizygotic twins have only an 8% risk of concordance, which is similar to the risk among other siblings.
Excessive thirst typically goes hand-in-hand with increased urination. As your body pulls water out of the tissues to dilute your blood and to rid your body of sugar through the urine, the urge to drink increases. Many people describe this thirst as an unquenchable one. To stay hydrated, you drink excessive amounts of liquids. And if those liquids contain simple sugars (soda, sweet iced tea, lemonade, or juice, for example) your sugars will skyrocket even higher.
The prognosis of diabetes is related to the extent to which the condition is kept under control to prevent the development of the complications described in the preceding sections. Some of the more serious complications of diabetes such as kidney failure and cardiovascular disease, can be life-threatening. Acute complications such as diabetic ketoacidosis can also be life-threatening. As mentioned above, aggressive control of blood sugar levels can prevent or delay the onset of complications, and many people with diabetes lead long and full lives.
Insulin is needed to allow glucose to pass from the blood into most of the body cells. Only the cells of the brain and central nervous system can use glucose from the blood in the absence of insulin. Without insulin, most body cells metabolize substances other than glucose for energy. However, fat metabolism in the absence of glucose metabolism, creates ketone bodies which are poisonous and their build up is associated with hyperglycemic coma. In the absence of sufficient insulin, unmetabolized glucose builds up in the blood. Water is drawn from body cells by osmosis to dilute the highly concentrated blood, and is then excreted along with much of the glucose, once the renal threshold for glucose (usually 10 mmol/L) is exceeded. Dehydration follows.
The most common cause of acquired blindness in many developed nations, diabetic retinopathy is rare in the prepubertal child or within 5 years of onset of diabetes. The prevalence and severity of retinopathy increase with age and are greatest in patients whose diabetic control is poor.  Prevalence rates seem to be declining, yet an estimated 80% of people with type 1 diabetes mellitus develop retinopathy. 
Abnormal cholesterol and triglyceride levels. If you have low levels of high-density lipoprotein (HDL), or "good," cholesterol, your risk of type 2 diabetes is higher. Triglycerides are another type of fat carried in the blood. People with high levels of triglycerides have an increased risk of type 2 diabetes. Your doctor can let you know what your cholesterol and triglyceride levels are.