a chronic metabolic disorder in which the use of carbohydrate is impaired and that of lipid and protein is enhanced. It is caused by an absolute or relative deficiency of insulin and is characterized, in more severe cases, by chronic hyperglycemia, glycosuria, water and electrolyte loss, ketoacidosis, and coma. Long-term complications include neuropathy, retinopathy, nephropathy, generalized degenerative changes in large and small blood vessels, and increased susceptibility to infection.
Type 1 Diabetes: About 5 to 10 percent of those with diabetes have type 1 diabetes. It's an autoimmune disease, meaning the body's own immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. Patients with type 1 diabetes have very little or no insulin, and must take insulin everyday. Although the condition can appear at any age, typically it's diagnosed in children and young adults, which is why it was previously called juvenile diabetes.
To measure blood glucose levels, a blood sample is usually taken after people have fasted overnight. However, it is possible to take blood samples after people have eaten. Some elevation of blood glucose levels after eating is normal, but even after a meal the levels should not be very high. Fasting blood glucose levels should never be higher than 125 mg/dL. Even after eating, blood glucose levels should not be higher than 199 mg/dL.
FIGURE 19-1 ■. This figure shows the hyperbolic relationship of insulin resistance and beta cell function. On the y-axis is beta cell function as reflected in the first-phase insulin response during intravenous (IV) glucose infusion; on the x-axis is insulin sensitivity and its mirror image resistance. In a subject with normal glucose tolerance (NGT) and beta-cell reserve, an increase in insulin resistance results in increased insulin release and normal glucose tolerance. In an individual for whom the capacity to increase insulin release is compromised, increasing insulin resistance with partial or no beta-cell compensation results in progression from normal glucose tolerance, to impaired glucose tolerance (IGT), and finally to diabetes (T2D). Differences between these categories are small at high insulin sensitivity, which may be maintained by weight reduction, exercise, and certain drugs. At a critical degree of insulin resistance, due to obesity or other listed factors, only a further small increment in resistance requires a large increase in insulin output. Those that can increase insulin secretion to this extent retain normal glucose tolerance; those who cannot achieve this degree of insulin secretion (e.g., due to a mild defect in genes regulating insulin synthesis, insulin secretion, insulin action, or an ongoing immune destruction of beta cells) now unmask varying degrees of carbohydrate intolerance. The product of insulin sensitivity (the reciprocal of insulin resistance) and acute insulin response (a measurement beta-cell function) has been called the “disposition index.” This index remains constant in an individual with normal beta cell compensation in response to changes in insulin resistance. IGT, impaired glucose tolerance; NGT, normal glucose tolerance; T2D, type 2 diabetes.

Jump up ^ Santaguida PL, Balion C, Hunt D, Morrison K, Gerstein H, Raina P, Booker L, Yazdi H. "Diagnosis, Prognosis, and Treatment of Impaired Glucose Tolerance and Impaired Fasting Glucose". Summary of Evidence Report/Technology Assessment, No. 128. Agency for Healthcare Research and Quality. Archived from the original on 16 September 2008. Retrieved 20 July 2008.
According to the American Diabetes Association, a child has a 1 in 7 risk of getting type 2 diabetes if his/her parent was diagnosed with type 2 diabetes before the age of 50, and a 1 in 13 risk of developing it if the parent was diagnosed after the age of 50. To see if you may be at risk for diabetes, consider taking this short and simple Type 2 Diabetes Risk Test from the ADA.
Management of type 2 diabetes focuses on lifestyle interventions, lowering other cardiovascular risk factors, and maintaining blood glucose levels in the normal range.[24] Self-monitoring of blood glucose for people with newly diagnosed type 2 diabetes may be used in combination with education,[70] however the benefit of self monitoring in those not using multi-dose insulin is questionable.[24][71] In those who do not want to measure blood levels, measuring urine levels may be done.[70] Managing other cardiovascular risk factors, such as hypertension, high cholesterol, and microalbuminuria, improves a person's life expectancy.[24] Decreasing the systolic blood pressure to less than 140 mmHg is associated with a lower risk of death and better outcomes.[72] Intensive blood pressure management (less than 130/80 mmHg) as opposed to standard blood pressure management (less than 140-160 mmHg systolic to 85–100 mmHg diastolic) results in a slight decrease in stroke risk but no effect on overall risk of death.[73]
Type 2 DM is characterized by insulin resistance, which may be combined with relatively reduced insulin secretion.[11] The defective responsiveness of body tissues to insulin is believed to involve the insulin receptor. However, the specific defects are not known. Diabetes mellitus cases due to a known defect are classified separately. Type 2 DM is the most common type of diabetes mellitus.[2]
In type 1 diabetes, other symptoms to watch for include unexplained weight loss, lethargy, drowsiness, and hunger. Symptoms sometimes occur after a viral illness. In some cases, a person may reach the point of diabetic ketoacidosis (DKA) before a type 1 diagnosis is made. DKA occurs when blood glucose is dangerously high and the body can't get nutrients into the cells because of the absence of insulin. The body then breaks down muscle and fat for energy, causing an accumulation of ketones in the blood and urine. Symptoms of DKA include a fruity odor on the breath; heavy, taxed breathing; and vomiting. If left untreated, DKA can result in stupor, unconsciousness, and even death.
Nerve damage (neuropathy). Excess sugar can injure the walls of the tiny blood vessels (capillaries) that nourish your nerves, especially in the legs. This can cause tingling, numbness, burning or pain that usually begins at the tips of the toes or fingers and gradually spreads upward. Poorly controlled blood sugar can eventually cause you to lose all sense of feeling in the affected limbs. Damage to the nerves that control digestion can cause problems with nausea, vomiting, diarrhea or constipation. For men, erectile dysfunction may be an issue.
Finally, modern society should probably shoulder at least some of the blame for the type 2 diabetes epidemic. Access to cheap, calorie-laden foods may even influence type 2 risk beyond simply their effects on body weight; the stuff that is in processed foods, like high-fructose corn syrup, could alter the body's chemistry or gut microbes in a way that affects health. Add to that the fact that most Americans are sedentary, spending their time sitting in cubicles, driving in cars, playing video games, or watching television. The lack of exercise, plus the abundance of unhealthy foods, cultivates a fertile breeding ground for diabetes.
Recognizing the symptoms of Type 1 diabetes is critical. Although Type 1 develops gradually, as the body’s insulin production decreases, blood glucose levels can become dangerously high once insulin production is outpaced. Symptoms may develop rapidly and can be mistaken for other illnesses such as the flu and a delayed diagnosis can have serious consequences.
How is it treated? There is no uniform therapy for type 2 diabetes treatment, which depends on the individual person and his or her stage of type 2 diabetes. To learn more about individualization of therapy, please read our patient guide. That said, the ADA and EASD have created treatment recommendation guidelines for type 2 diabetes progression. In all cases, healthy eating, exercise, and weight management are key to effective type 2 diabetes management. As type 2 diabetes progresses, patients may need to add one or more drugs to their treatment regimen.
Type 1 Diabetes: About 5 to 10 percent of those with diabetes have type 1 diabetes. It's an autoimmune disease, meaning the body's own immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas. Patients with type 1 diabetes have very little or no insulin, and must take insulin everyday. Although the condition can appear at any age, typically it's diagnosed in children and young adults, which is why it was previously called juvenile diabetes.
There is no single gene that “causes” type 1 diabetes. Instead, there are a large number of inherited factors that may increase an individual’s likelihood of developing diabetes. This is known as multifactorial inheritance. The genes implicated in the development of type 1 diabetes mellitus control the human leukocyte antigen (HLA) system. This system is involved in the complex process of identifying cells which are a normal part of the body, and distinguishing them from foreign cells, such as those of bacteria or viruses. In an autoimmune disease such as diabetes mellitus, this system makes a mistake in identifying the normal ‘self’ cells as ‘foreign’, and attacks the body.  
Findings from the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS) have clearly shown that aggressive and intensive control of elevated levels of blood sugar in patients with type 1 and type 2 diabetes decreases the complications of nephropathy, neuropathy, retinopathy, and may reduce the occurrence and severity of large blood vessel diseases. Aggressive control with intensive therapy means achieving fasting glucose levels between 70-120 mg/dl; glucose levels of less than 160 mg/dl after meals; and a near normal hemoglobin A1c levels (see below).
When there is excess glucose present in the blood, as with type 2 diabetes, the kidneys react by flushing it out of the blood and into the urine. This results in more urine production and the need to urinate more frequently, as well as an increased risk of urinary tract infections (UTIs) in men and women. People with type 2 diabetes are twice as likely to get a UTI as people without the disease, and the risk is higher in women than in men.