The definition of a genetic disease is a disorder or condition caused by abnormalities in a person's genome. Some types of genetic inheritance include single inheritance, including cystic fibrosis, sickle cell anemia, Marfan syndrome, and hemochromatosis. Other types of genetic diseases include multifactorial inheritance. Still other types of genetic diseases include chromosome abnormalities (for example, Turner syndrome, and Klinefelter syndrome), and mitochondrial inheritance (for example, epilepsy and dementia).
There are other factors that also fall into the category of environmental (as opposed to genetic) causes of diabetes. Certain injuries to the pancreas, from physical trauma or from drugs, can harm beta cells, leading to diabetes. Studies have also found that people who live in polluted areas are prone to type 2, perhaps because of inflammation. And an alternate theory of insulin resistance places the blame on damage caused by inflammation. Age also factors into type 2; beta cells can wear out over time and become less capable of producing enough insulin to overcome insulin resistance, which is why older people are at greater risk of type 2.

About 40% of diabetes sufferers require oral agents for satisfactory blood glucose control, and some 40% need insulin injections. This hormone was isolated by Frederic Banting and Charles Best in 1921 in Canada. It revolutionized the treatment of diabetes and prevention of its complications, transforming Type 1 diabetes from a fatal disease to one in which long-term survival became achievable.
Your risk for Type 2 diabetes increases as you get older. It also increases if you smoke. Although smoking doesn't cause diabetes per se, the negative effects on your health are enough to make it more likely that Type 2 diabetes will occur if you have the other risk factors. "We try to be aggressive with smoking cessation, in particular in patients with diabetes," says Dr. Asha M. Thomas, an endocrinologist with Sinai Hospital of Baltimore.
The primary complications of diabetes due to damage in small blood vessels include damage to the eyes, kidneys, and nerves.[32] Damage to the eyes, known as diabetic retinopathy, is caused by damage to the blood vessels in the retina of the eye, and can result in gradual vision loss and eventual blindness.[32] Diabetes also increases the risk of having glaucoma, cataracts, and other eye problems. It is recommended that diabetics visit an eye doctor once a year.[33] Damage to the kidneys, known as diabetic nephropathy, can lead to tissue scarring, urine protein loss, and eventually chronic kidney disease, sometimes requiring dialysis or kidney transplantation.[32] Damage to the nerves of the body, known as diabetic neuropathy, is the most common complication of diabetes.[32] The symptoms can include numbness, tingling, pain, and altered pain sensation, which can lead to damage to the skin. Diabetes-related foot problems (such as diabetic foot ulcers) may occur, and can be difficult to treat, occasionally requiring amputation. Additionally, proximal diabetic neuropathy causes painful muscle atrophy and weakness.
The word diabetes (/ˌdaɪ.əˈbiːtiːz/ or /ˌdaɪ.əˈbiːtɪs/) comes from Latin diabētēs, which in turn comes from Ancient Greek διαβήτης (diabētēs), which literally means "a passer through; a siphon".[111] Ancient Greek physician Aretaeus of Cappadocia (fl. 1st century CE) used that word, with the intended meaning "excessive discharge of urine", as the name for the disease.[112][113] Ultimately, the word comes from Greek διαβαίνειν (diabainein), meaning "to pass through,"[111] which is composed of δια- (dia-), meaning "through" and βαίνειν (bainein), meaning "to go".[112] The word "diabetes" is first recorded in English, in the form diabete, in a medical text written around 1425.

The term brittle diabetes has been used to refer to people who have dramatic recurrent swings in blood glucose levels, often for no apparent reason. However, this term is no longer used. People with type 1 diabetes may have more frequent swings in blood glucose levels because insulin production is completely absent. Infection, delayed movement of food through the stomach, and other hormonal disorders may also contribute to blood glucose swings. In all people who have difficulty controlling blood glucose, doctors look for other disorders that might be causing the problem and also give people additional education on how to monitor diabetes and take their drugs.
observations The onset of type 1 diabetes mellitus is sudden in children. Type 2 diabetes often begins insidiously. Characteristically the course is progressive and includes polyuria, polydipsia, weight loss, polyphagia, hyperglycemia, and glycosuria. The eyes, kidneys, nervous system, skin, and circulatory system may be affected by the long-term complications of either type of diabetes; infections are common; and atherosclerosis often develops. In type 1 diabetes mellitus, when no endogenous insulin is being secreted, ketoacidosis is a constant danger. The diagnosis is confirmed by fasting plasma glucose and history.
The Diabetes Control and Complications Trial (DCCT) was a clinical study conducted by the United States National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) that was published in the New England Journal of Medicine in 1993. Test subjects all had diabetes mellitus type 1 and were randomized to a tight glycemic arm and a control arm with the standard of care at the time; people were followed for an average of seven years, and people in the treatment had dramatically lower rates of diabetic complications. It was as a landmark study at the time, and significantly changed the management of all forms of diabetes.[86][130][131]
People usually develop type 2 diabetes after the age of 40 years, although people of South Asian origin are at an increased risk of the condition and may develop diabetes from the age of 25 onwards. The condition is also becoming increasingly common among children and adolescents across all populations. Type 2 diabetes often develops as a result of overweight, obesity and lack of physical activity and diabetes prevalence is on the rise worldwide as these problems become more widespread.
Most cases (95%) of type 1 diabetes mellitus are the result of environmental factors interacting with a genetically susceptible person. This interaction leads to the development of autoimmune disease directed at the insulin-producing cells of the pancreatic islets of Langerhans. These cells are progressively destroyed, with insulin deficiency usually developing after the destruction of 90% of islet cells.
To diagnose diabetes, doctors will  take a medical history (ask you about symptoms) and ask for blood and urine samples. Finding protein and sugar in the urine are signs of type 2 diabetes. Increased glucose and triglyceride (a type of lipid or fat) levels in the blood are also common findings. In most cases, blood glucose levels are checked after a person has been fasting for 8 hours.
Jump up ^ Feinman, RD; Pogozelski, WK; Astrup, A; Bernstein, RK; Fine, EJ; Westman, EC; Accurso, A; Frassetto, L; Gower, BA; McFarlane, SI; Nielsen, JV; Krarup, T; Saslow, L; Roth, KS; Vernon, MC; Volek, JS; Wilshire, GB; Dahlqvist, A; Sundberg, R; Childers, A; Morrison, K; Manninen, AH; Dashti, HM; Wood, RJ; Wortman, J; Worm, N (January 2015). "Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base". Nutrition. Burbank, Los Angeles County, Calif. 31 (1): 1–13. doi:10.1016/j.nut.2014.06.011. PMID 25287761.
Diabetic ketoacidosis can be caused by infections, stress, or trauma, all of which may increase insulin requirements. In addition, missing doses of insulin is also an obvious risk factor for developing diabetic ketoacidosis. Urgent treatment of diabetic ketoacidosis involves the intravenous administration of fluid, electrolytes, and insulin, usually in a hospital intensive care unit. Dehydration can be very severe, and it is not unusual to need to replace 6-7 liters of fluid when a person presents in diabetic ketoacidosis. Antibiotics are given for infections. With treatment, abnormal blood sugar levels, ketone production, acidosis, and dehydration can be reversed rapidly, and patients can recover remarkably well.
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A growing number of people in the U.S. and throughout the world are overweight and more prone to develop Type 2 diabetes, particularly if they have the genetics for it. "Type 2 diabetes can be caused by genetic inheritance, but by far the obesity epidemic has created massive increases in the occurrence of Type 2 diabetes. This is due to the major insulin resistance that is created by obesity," Gage says.
When you have type 2 diabetes, your cells don't get enough glucose, which may cause you to lose weight. Also, if you are urinating more frequently because of uncontrolled diabetes, you may lose more calories and water, resulting in weight loss, says Daniel Einhorn, MD, medical director of the Scripps Whittier Diabetes Institute and clinical professor of medicine at the University of California in San Diego.