The causes of diabetes mellitus are unclear, however, there seem to be both hereditary (genetic factors passed on in families) and environmental factors involved. Research has shown that some people who develop diabetes have common genetic markers. In Type I diabetes, the immune system, the body's defense system against infection, is believed to be triggered by a virus or another microorganism that destroys cells in the pancreas that produce insulin. In Type II diabetes, age, obesity, and family history of diabetes play a role.
Diabetes mellitus, or as it's more commonly known diabetes, is a disease characterized by an excess of blood glucose, or blood sugar, which builds up in the bloodstream when your body isn't able to adequately process the sugar in food. High blood sugar is an abnormal state for the body and creates specific symptoms and possible long-term health problems if blood sugar is not managed well.
Other studies have focused, not on sugar overall but specifically on sodas and other sugar-sweetened beverages. Many have found no significant relationship, apart from sugar’s extra calories that lead to weight gain. For example, the Women’s Health Study,8 the Atherosclerosis Risk in Communities Study,9 the Black Women’s Health Study,10 and the Multi-Ethnic Study of Atherosclerosis found no significant associations between sugar consumption and diabetes risk after adjustment for measures of body weight. Some studies have had mixed results, exonerating sucrose, but indicting glucose and fructose.12,13 And some studies have shown associations between sugar-sweetened beverages and diabetes that persist after adjustment for body weight.14,15

Studies show that good control of blood sugar levels decreases the risk of complications from diabetes.  Patients with better control of blood sugar have reduced rates of diabetic eye disease, kidney disease, and nerve disease. It is important for patients to measure their measuring blood glucose levels. Hemoglobin A1c can also be measured with a blood test and gives information about average blood glucose over the past 3 months. 
^ Jump up to: a b Cheng, J; Zhang, W; Zhang, X; Han, F; Li, X; He, X; Li, Q; Chen, J (May 2014). "Effect of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on all-cause mortality, cardiovascular deaths, and cardiovascular events in patients with diabetes mellitus: a meta-analysis". JAMA Internal Medicine. 174 (5): 773–85. doi:10.1001/jamainternmed.2014.348. PMID 24687000.
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.
While there is a strong genetic component to developing this form of diabetes, there are other risk factors - the most significant of which is obesity. There is a direct relationship between the degree of obesity and the risk of developing type 2 diabetes, and this holds true in children as well as adults. It is estimated that the chance to develop diabetes doubles for every 20% increase over desirable body weight.
A population-based, nationwide cohort study in Finland examined the short -and long-term time trends in mortality among patients with early-onset and late-onset type 1 diabetes. The results suggest that in those with early-onset type 1 diabetes (age 0-14 y), survival has improved over time. Survival of those with late-onset type 1 diabetes (15-29 y) has deteriorated since the 1980s, and the ratio of deaths caused by acute complications has increased in this group. Overall, alcohol was noted as an important cause of death in patients with type 1 diabetes; women had higher standardized mortality ratios than did men in both groups. [38]
Diabetes has been recorded throughout history, since Egyptian times. It was given the name diabetes by the ancient Greek physician Aratus of Cappadocia. The full term, however, was not coined until 1675 in Britain by Thomas Willis, who rediscovered that the blood and urine of people with diabetes were sweet. This phenomenon had previously been discovered by ancient Indians.
Low blood sugar (hypoglycemia). If your blood sugar level drops below your target range, it's known as low blood sugar (hypoglycemia). Your blood sugar level can drop for many reasons, including skipping a meal, inadvertently taking more medication than usual or getting more physical activity than normal. Low blood sugar is most likely if you take glucose-lowering medications that promote the secretion of insulin or if you're taking insulin.
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]

Being too heavy gets the bulk of the blame for triggering type 2 diabetes. According to the National Institutes of Health, about 85 percent of people with type 2 diabetes are overweight or obese. But consider that the remaining 15 percent are not. Consider, too, that roughly two-thirds of overweight people and a third of those who are obese will never develop diabetes. In other words, normal-weight and thin people also develop type 2, while heavy people won't necessarily. Clearly, there is more to the connection between lifestyle and type 2 diabetes than just body size.

They may need to take medications in order to keep glucose levels within a healthy range. Medications for type 2 diabetes are usually taken by mouth in the form of tablets and should always be taken around meal times and as prescribed by the doctor. However, if blood glucose is not controlled by oral medications, a doctor may recommend insulin injections.
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]

Prevention and treatment involve maintaining a healthy diet, regular physical exercise, a normal body weight, and avoiding use of tobacco.[2] Control of blood pressure and maintaining proper foot care are important for people with the disease.[2] Type 1 DM must be managed with insulin injections.[2] Type 2 DM may be treated with medications with or without insulin.[9] Insulin and some oral medications can cause low blood sugar.[13] Weight loss surgery in those with obesity is sometimes an effective measure in those with type 2 DM.[14] Gestational diabetes usually resolves after the birth of the baby.[15]
Clinical Manifestations. Diabetes mellitus can present a wide variety of symptoms, from none at all to profound ketosis and coma. If the disease manifests itself late in life, patients may not know they have it until it is discovered during a routine examination, or when the symptoms of chronic vascular disease, insidious renal failure, or impaired vision cause them to seek medical help.
Reduce Your Carbohydrate Intake: One of the most important components involved in a diabetes diet is knowing how to eat a modified carbohydrate diet. Carbohydrates are the nutrient that impacts blood sugars the most. Carbohydrates are found in starches, fruit, some vegetables like potatoes, sweets, and grains. Eating the right kinds of carbohydrate in the right quantities can help you manage your weight and your blood sugars. Knowing how to identify and count carbohydrates is very important in managing diabetes. Eating a consistent carbohydrate diet is ideal because it can help you body regulate blood sugars.
By simultaneously considering insulin secretion and insulin action in any given individual, it becomes possible to account for the natural history of diabetes in that person (e.g., remission in a patient with T1 diabetes or ketoacidosis in a person with T2DM). Thus, diabetes mellitus may be the result of absolute insulin deficiency, or of absolute insulin resistance, or a combination of milder defects in both insulin secretion and insulin action.1 Collectively, the syndromes of diabetes mellitus are the most common endocrine/metabolic disorders of childhood and adolescence. The application of molecular biologic tools continues to provide remarkable insights into the etiology, pathophysiology, and genetics of the various forms of diabetes mellitus that result from deficient secretion of insulin or its action at the cellular level.
Rates of type 2 diabetes have increased markedly since 1960 in parallel with obesity.[17] As of 2015 there were approximately 392 million people diagnosed with the disease compared to around 30 million in 1985.[11][18] Typically it begins in middle or older age,[6] although rates of type 2 diabetes are increasing in young people.[19][20] Type 2 diabetes is associated with a ten-year-shorter life expectancy.[10] Diabetes was one of the first diseases described.[21] The importance of insulin in the disease was determined in the 1920s.[22]

Diabetes mellitus is a metabolic condition in which a person's blood sugar (glucose) levels are too high. Over 29.1 million children and adults in the US have diabetes. Of that, 8.1 million people have diabetes and don't even know it. Type 1 diabetes (insulin-dependent, juvenile) is caused by a problem with insulin production by the pancreas. Type 2 diabetes (non-insulin dependent) is caused by:
Glucose in your body can cause yeast infections. This is because glucose speeds the growth of fungus. There are over-the-counter and prescription medications to treat yeast infections. You can potentially avoid yeast infections by maintaining better control of your blood sugar. Take insulin as prescribed, exercise regularly, reduce your carb intake, choose low-glycemic foods, and monitor your blood sugar.