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.
Insulin resistance is the most common cause of type 2 diabetes, but it is possible to have type 2 and not be insulin resistant. You can have a form of type 2 where you body simply doesn’t produce enough insulin; that’s not as common. Researchers aren’t sure what exactly keeps some people from producing enough insulin, but that’s another thing they’re working hard to figure out.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

Infections. Poorly controlled diabetes can lead to a variety of tissue infections. The most commonly encountered is a yeast infection (Candida) and the presence of dry mouth further increases one’s risk (see PATIENT INFORMATION SHEET – Oral Yeast Infections). Typically, affected areas appear redder than the surrounding tissue and commonly affected sites include the tongue, palate, cheeks, gums, or corners of the mouth (see Right). There is conflicting data regarding cavity risk in the diabetic patient, but those who have dry mouth are clearly at increased risk for developing cavities.
Having diabetes requires life-long treatment and follow-up by health professionals. Diabetes can be linked to damage of the eyes, kidneys and feet. It is also associated with increased risk of strokes, heart attacks and poor blood circulation to the legs. Medical care aims to minimise these risks by controlling diabetes, blood pressure and cholesterol and screening for possible complications caused by the diabetes. 

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]
Type 1 diabetes occurs because the insulin-producing cells of the pancreas (beta cells) are damaged. In type 1 diabetes, the pancreas makes little or no insulin, so sugar cannot get into the body's cells for use as energy. People with type 1 diabetes must use insulin injections to control their blood glucose. Type 1 is the most common form of diabetes in people who are under age 30, but it can occur at any age. Ten percent of people with diabetes are diagnosed with type 1.
Brittle diabetics are a subgroup of Type I where patients have frequent and rapid swings of blood sugar levels between hyperglycemia (a condition where there is too much glucose or sugar in the blood) and hypoglycemia (a condition where there are abnormally low levels of glucose or sugar in the blood). These patients may require several injections of different types of insulin during the day to keep the blood sugar level within a fairly normal range.
Diabetes mellitus is a condition in which the body does not produce enough of the hormone insulin, resulting in high levels of sugar in the bloodstream. There are many different types of diabetes; the most common are type 1 and type 2 diabetes, which are covered in this article. Gestational diabetes occurs during the second half of pregnancy and is covered in a separate article. Diabetes can also be caused by disease or damage to the pancreas, Cushing's syndrome, acromegaly and there are also some rare genetic forms.

Diagnosis. The most common diagnostic tests for diabetes are chemical analyses of the blood such as the fasting plasma glucose. Capillary blood glucose monitoring can be used for screening large segments of the population. Portable equipment is available and only one drop of blood from the fingertip or earlobe is necessary. Capillary blood glucose levels have largely replaced analysis of the urine for glucose. Testing for urinary glucose can be problematic as the patient may have a high renal threshold, which would lead to a negative reading for urinary glucose when in fact the blood glucose level was high.
Insulin is released into the blood by beta cells (β-cells), found in the islets of Langerhans in the pancreas, in response to rising levels of blood glucose, typically after eating. Insulin is used by about two-thirds of the body's cells to absorb glucose from the blood for use as fuel, for conversion to other needed molecules, or for storage. Lower glucose levels result in decreased insulin release from the beta cells and in the breakdown of glycogen to glucose. This process is mainly controlled by the hormone glucagon, which acts in the opposite manner to insulin.[61]
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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.