a broadly applied term used to denote a complex group of syndromes that have in common a disturbance in the oxidation and utilization of glucose, which is secondary to a malfunction of the beta cells of the pancreas, whose function is the production and release of insulin. Because insulin is involved in the metabolism of carbohydrates, proteins and fats, diabetes is not limited to a disturbance of glucose homeostasis alone.
George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) is a member of the following medical societies: American Academy of Pediatrics, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Pediatric Endocrine Society, Society for Pediatric Research, American College of Endocrinology
Many older people have difficulty following a healthy, balanced diet that can control blood glucose levels and weight. Changing long-held food preferences and dietary habits may be hard. Some older people have other disorders that can be affected by diet and may not understand how to integrate the dietary recommendations for their various disorders.

Type 1 diabetes is always treated with insulin, a life-saving treatment. Patients will need to take insulin several times a day for the rest of their lives. They will usually learn how to self-administer this. Insulin is usually given through injections under the skin, normally two to four times a day. An increasing number of patients with type 1 diabetes are being treated with ‘insulin pumps’, which provide a continuous supply of insulin. 
Jump up ^ Qaseem, Amir; Wilt, Timothy J.; Kansagara, Devan; Horwitch, Carrie; Barry, Michael J.; Forciea, Mary Ann (6 March 2018). "Hemoglobin A Targets for Glycemic Control With Pharmacologic Therapy for Nonpregnant Adults With Type 2 Diabetes Mellitus: A Guidance Statement Update From the American College of Physicians". Annals of Internal Medicine. doi:10.7326/M17-0939.
Blurred vision can result from elevated blood sugar. Similarly, fluid that is pulled from the cells into the bloodstream to dilute the sugar can also be pulled from the lenses of your eyes. When the lens of the eye becomes dry, the eye is unable to focus, resulting in blurry vision. It's important that all people diagnosed with type 2 diabetes have a dilated eye exam shortly after diagnosis. Damage to the eye can even occur before a diagnosis of diabetes exists.

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.

Maturity onset diabetes of the young (MODY) is a rare autosomal dominant inherited form of diabetes, due to one of several single-gene mutations causing defects in insulin production.[52] It is significantly less common than the three main types. The name of this disease refers to early hypotheses as to its nature. Being due to a defective gene, this disease varies in age at presentation and in severity according to the specific gene defect; thus there are at least 13 subtypes of MODY. People with MODY often can control it without using insulin.
Inhalable insulin has been developed.[125] The original products were withdrawn due to side effects.[125] Afrezza, under development by the pharmaceuticals company MannKind Corporation, was approved by the United States Food and Drug Administration (FDA) for general sale in June 2014.[126] An advantage to inhaled insulin is that it may be more convenient and easy to use.[127]
Although many of the symptoms of type 1 and type 2 diabetes are similar, they present in very different ways. Many people with type 2 diabetes won’t have symptoms for many years. Then often the symptoms of type 2 diabetes develop slowly over the course of time. Some people with type 2 diabetes have no symptoms at all and don’t discover their condition until complications develop.
Diabetes mellitus (“diabetes”) and hypertension, which commonly coexist, are global public health issues contributing to an enormous burden of cardiovascular disease, chronic kidney disease, and premature mortality and disability. The presence of both conditions has an amplifying effect on risk for microvascular and macrovascular complications.1 The prevalence of diabetes is rising worldwide (Fig. 37.1). Both diabetes and hypertension disproportionately affect people in middle and low-income countries, and an estimated 70% of all cases of diabetes are found in these countries.2,3 In the United States alone, the total costs of care for diabetes and hypertension in the years 2012 and 2011 were 245 and 46 billion dollars, respectively.4,5 Therefore, there is a great potential for meaningful health and economic gains attached to prevention, detection, and intervention for diabetes and hypertension.
No single environmental trigger has been identified as causing diabetes mellitus, however both infectious agents and dietary factors are thought to be important. Various viruses have been implicated in the development of type I DM. They may act by initiating or modifying the autoimmune process. In particular, the rubella virus and coxsackie viruses have been closely studied. In particular, congenital rubella infection has shown direct relationships with the development of type 1 diabetes mellitus. This is presumably due to the virus (or antibodies against it) damaging the beta cells of the pancreas. Some research has looked at dietary factors that may be associated with type 1 diabetes. In particular, cow’s milk proteins (such as bovine serum albumin) which may have some similarities to pancreatic islet cell markers may be able to trigger the autoimmune process. Other chemicals including nitrosamines have been identified as causes of diabetes mellitus in animal models, but not in humans.
Type 2 diabetes: Type 2 diabetes affects the way the body uses insulin. While the body still makes insulin, unlike in type I, the cells in the body do not respond to it as effectively as they once did. This is the most common type of diabetes, according to the National Institute of Diabetes and Digestive and Kidney Diseases, and it has strong links with obesity.
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.
Low testosterone (low-T) can be caused by conditions such as type 2 diabetes, obesity, liver or kidney disease, hormonal disorders, certain infections, and hypogonadism. Signs and symptoms that a person may have low-T include insomnia, increased body fat, weight gain, reduced muscle, infertility, decreased sex drive, depression, and worsening of congestive heart failure or sleep apnea.
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).[62] 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).[60]

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. [14] Prevalence rates seem to be declining, yet an estimated 80% of people with type 1 diabetes mellitus develop retinopathy. [15]
Type 1 diabetes occurs when the immune system attacks and destroys the insulin-producing cells in the pancreas (the beta cells). As a result, the body is left without enough insulin to function normally (i.e. it becomes insulin deficient). This is called an autoimmune reaction, because the body attacks itself and produces antibodies to its own insulin-producing cells, thereby destroying them.

Dr. Erica Oberg, ND, MPH, received a BA in anthropology from the University of Colorado, her doctorate of naturopathic medicine (ND) from Bastyr University, and a masters of public health (MPH) in health services research from the University of Washington. She completed her residency at the Bastyr Center for Natural Health in ambulatory primary care and fellowship training at the Health Promotion Research Center at the University of Washington.
Dr. Erica Oberg, ND, MPH, received a BA in anthropology from the University of Colorado, her doctorate of naturopathic medicine (ND) from Bastyr University, and a masters of public health (MPH) in health services research from the University of Washington. She completed her residency at the Bastyr Center for Natural Health in ambulatory primary care and fellowship training at the Health Promotion Research Center at the University of Washington.
If the amount of insulin available is insufficient, or if cells respond poorly to the effects of insulin (insulin insensitivity or insulin resistance), or if the insulin itself is defective, then glucose will not be absorbed properly by the body cells that require it, and it will not be stored appropriately in the liver and muscles. The net effect is persistently high levels of blood glucose, poor protein synthesis, and other metabolic derangements, such as acidosis.[60]
Diabetes insipidus is characterized by excessive urination and thirst, as well as a general feeling of weakness. While these can also be symptoms of diabetes mellitus, if you have diabetes insipidus your blood sugar levels will be normal and no sugar present in your urine. Diabetes insipidus is a problem of fluid balance caused by a problem with the kidneys, where they can't stop the excretion of water. Polyuria (excessive urine) and polydipsia (excessive thirst) occur in diabetes mellitus as a reaction to high blood sugar.
Type II is considered a milder form of diabetes because of its slow onset (sometimes developing over the course of several years) and because it usually can be controlled with diet and oral medication. The consequences of uncontrolled and untreated Type II diabetes, however, are the just as serious as those for Type I. This form is also called noninsulin-dependent diabetes, a term that is somewhat misleading. Many people with Type II diabetes can control the condition with diet and oral medications, however, insulin injections are sometimes necessary if treatment with diet and oral medication is not working.

Type 2 diabetes is usually associated with being overweight (BMI greater than 25), and is harder to control when food choices are not adjusted, and you get no physical activity. And while it’s true that too much body fat and physical inactivity (being sedentary) does increase the likelihood of developing type 2, even people who are fit and trim can develop this type of diabetes.2,3
But preventing the disease from progressing if you already have it requires first being able to spot the signs and symptoms of diabetes when they appear. While some type 2 diabetes symptoms may not ever show up, you can watch out for the following common signs of the disease and alert your doctor, especially if you have any of the common risk factors for diabetes. Also keep in mind that while most signs of type 2 diabetes are the same in men and women, there are some distinctions.