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.
Type 2 DM begins with insulin resistance, a condition in which cells fail to respond to insulin properly. As the disease progresses, a lack of insulin may also develop. This form was previously referred to as "non insulin-dependent diabetes mellitus" (NIDDM) or "adult-onset diabetes". The most common cause is excessive body weight and insufficient exercise.
Family or personal history. Your risk increases if you have prediabetes — a precursor to type 2 diabetes — or if a close family member, such as a parent or sibling, has type 2 diabetes. You're also at greater risk if you had gestational diabetes during a previous pregnancy, if you delivered a very large baby or if you had an unexplained stillbirth.
Getting diagnosed with diabetes can be shocking, but the good news is that, although it is a disease you must deal with daily, it is a manageable one. If you are experiencing any of the above symptoms, especially if you are someone who is at high risk, you should meet with your primary care physician to get tested. The earlier a diagnosis is made, the more likely you can get your diabetes under control and prevent complications.
According to the National Institutes of Health, the reported rate of gestational diabetes is between 2% to 10% of pregnancies. Gestational diabetes usually resolves itself after pregnancy. Having gestational diabetes does, however, put mothers at risk for developing type 2 diabetes later in life. Up to 10% of women with gestational diabetes develop type 2 diabetes. It can occur anywhere from a few weeks after delivery to months or years later.
The typical symptoms of diabetes mellitus are the three “polys:” polyuria, polydipsia, and polyphagia. Because of insulin deficiency, the assimilation and storage of glucose in muscle adipose tissues, and the liver is greatly diminished. This produces an accumulation of glucose in the blood and creates an increase in its osmolarity. In response to this increased osmotic pressure there is depletion of intracellular water and osmotic diuresis. The water loss creates intense thirst and increased urination. The increased appetite (polyphagia) is not as clearly understood. It may be the result of the body's effort to increase its supply of energy foods even though eating more carbohydrates in the absence of sufficient insulin does not meet the energy needs of the cells.
When you have diabetes, it’s important to avoid eating many packaged, processed snacks such as cookies, chips, cake, granola bars, and the like, in lieu of fresh, whole foods, like fiber-rich fruits, veggies, and whole grains. (27) Eating foods high in fiber can help keep blood sugar levels steady and fill you up, potentially promoting weight loss and improving insulin sensitivity. (28)
Diabetes has been coined the “silent killer” because the symptoms are so easy to miss. Over 24 million people in America have diabetes, so this is no tiny issue. Kids years ago hardly ever knew another child with diabetes, but such is no longer the case. Approximately 1.25 million children in the United States living with diabetes, which is very telling for state of health in America in 2016 when children are having to endure a medical lifestyle at such a young age.
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.
All types of diabetes mellitus have something in common. Normally, your body breaks down the sugars and carbohydrates you eat into a special sugar called glucose. Glucose fuels the cells in your body. But the cells need insulin, a hormone, in your bloodstream in order to take in the glucose and use it for energy. With diabetes mellitus, either your body doesn't make enough insulin, it can't use the insulin it does produce, or a combination of both.
Insulin is essential to process carbohydrates, fat, and protein. Insulin reduces blood glucose levels by allowing glucose to enter muscle cells and by stimulating the conversion of glucose to glycogen (glycogenesis) as a carbohydrate store. Insulin also inhibits the release of stored glucose from liver glycogen (glycogenolysis) and slows the breakdown of fat to triglycerides, free fatty acids, and ketones. It also stimulates fat storage. Additionally, insulin inhibits the breakdown of protein and fat for glucose production (gluconeogenesis) in the liver and kidneys.
Type 1 and type 2 diabetes were identified as separate conditions for the first time by the Indian physicians Sushruta and Charaka in 400–500 AD with type 1 associated with youth and type 2 with being overweight. The term "mellitus" or "from honey" was added by the Briton John Rolle in the late 1700s to separate the condition from diabetes insipidus which is also associated with frequent urination. Effective treatment was not developed until the early part of the 20th century when the Canadians Frederick Banting and Charles Best discovered insulin in 1921 and 1922. This was followed by the development of the long acting NPH insulin in the 1940s.
It is a considerable challenge to obtain the goals of the intensively treated patients in the DCCT with the vast majority of people with diabetes given the more limited health care resources typically available in routine practice. If diabetes control can be improved without significant damage to quality of life, the economic, health, and quality of life savings associated with a reduction in complications in later life will be vast. Although some people who have had poorly controlled diabetes over many years do not develop complications, complications commonly arise after 15–20 years of diabetes and individuals in their 40s or even 30s may develop several complications in rapid succession. However, up until the early 1980s, patients had no way of monitoring their own blood glucose levels at home. Urine glucose monitoring only told them when their blood glucose had exceeded the renal threshold of approximately 10 mmol/L (i.e., was far too high), without being able to discriminate between the too high levels of 7–10 mmol/L or the hypoglycemic levels below 4 mmol/L. Clinics relied on random blood glucose testing and there were no measures of average blood glucose over a longer period. Since the 1980s there have been measures of glycosylated hemoglobin (GHb, HbA1, or HbA1c) which indicate average blood glucose over a six to eight week period and measures of glycosylated protein, fructosamine, which indicates average blood glucose over a two-week period. Blood-glucose meters for patients were first introduced in the early 1980s and the accuracy and convenience of the meters and the reagent strips they use has improved dramatically since early models. By the late 1990s blood-glucose monitoring is part of the daily routine for most people using insulin in developed countries. Blood-glucose monitoring is less often prescribed for tablet- and diet-alone-treated patients, financial reasons probably being allowed to outweigh the educational value of accurate feedback in improving control long term. The reduced risk of hypoglycemia and diabetic ketoacidosis in NIDDM patients not using insulin means that acute crises rarely arise in these patients though their risk of long-term complications is at least as great as in IDDM and might be expected to be reduced if feedback from blood-glucose monitoring were provided.
Oral glucose tolerance test (OGTT): With this test you will be required to fast for at least 8 hours and then are given a drink with 75 g of carbohydrate. Your blood glucose is checked at fasting and then 2 hours after drinking the solution. If your blood glucose is 11.1 mmol/L or higher, your doctor may diagnose diabetes. If your blood glucose 2 hours after drinking the solution is between 7.8 to 11.1 mmol/L, your doctor may diagnose prediabetes. This is the preferred method to test for gestational diabetes.
People with Type 1 diabetes are usually totally dependent on insulin injections for survival. Such people require daily administration of insulin. The majority of people suffering from diabetes have the Type 2 form. Although they do not depend on insulin for survival, about one third of sufferers needs insulin for reducing their blood glucose levels.
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.
Autonomic changes involving cardiovascular control (eg, heart rate, postural responses) have been described in as many as 40% of children with diabetes. Cardiovascular control changes become more likely with increasing duration and worsening control.  In a study by 253 patients with type 1 diabetes (mean age at baseline 14.4 y), Cho et al reported that the prevalence of cardiac autonomic dysfunction increases in association with higher body mass index and central adiposity. 
Type 2 DM is primarily due to lifestyle factors and genetics. A number of lifestyle factors are known to be important to the development of type 2 DM, including obesity (defined by a body mass index of greater than 30), lack of physical activity, poor diet, stress, and urbanization. Excess body fat is associated with 30% of cases in those of Chinese and Japanese descent, 60–80% of cases in those of European and African descent, and 100% of Pima Indians and Pacific Islanders. Even those who are not obese often have a high waist–hip ratio.
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.
Supporting evidence for Shulman's theory comes from observations about a rare genetic illness called lipodystrophy. People with lipodystrophy can't make fat tissue, which is where fat should properly be stored. These thin people also develop severe insulin resistance and type 2 diabetes. "They have fat stored in places it doesn't belong," like the liver and muscles, says Shulman. "When we treat them . . . we melt the fat away, reversing insulin resistance and type 2 diabetes." Shulman's theory also suggests why some people who carry extra fat don't get type 2. "There are some individuals who store fat [under the skin] who have relatively normal insulin sensitivity, a so-called fit fat individual," he says. Because of the way their bodies store fat, he believes, they don't get diabetes.
Because type 2 diabetes is linked to high levels of sugar in the blood, it may seem logical to assume that eating too much sugar is the cause of the disease. But of course, it’s not that simple. “This has been around for years, this idea that eating too much sugar causes diabetes — but the truth is, type 2 diabetes is a multifactorial disease with many different types of causes,” says Lynn Grieger, RDN, CDE, a nutrition coach in Prescott, Arizona, and a medical reviewer for Everyday Health. “Type 2 diabetes is really complex.”
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.
In addition to learning about diabetes itself, older people may have to learn how to fit management of diabetes in with their management of other disorders. Learning about how to avoid complications, such as dehydration, skin breakdown, and circulation problems, and to manage factors that can contribute to complications of diabetes, such as high blood pressure and high cholesterol levels, is especially important. Such problems become more common as people age, whether they have diabetes or not.
Jump up ^ Kyu HH, Bachman VF, Alexander LT, Mumford JE, Afshin A, Estep K, Veerman JL, Delwiche K, Iannarone ML, Moyer ML, Cercy K, Vos T, Murray CJ, Forouzanfar MH (August 2016). "Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013". BMJ. 354: i3857. doi:10.1136/bmj.i3857. PMC 4979358. PMID 27510511.
How does type 2 diabetes progress over time? Type 2 diabetes is a progressive disease, meaning that the body’s ability to regulate blood sugar gets worse over time, despite careful management. Over time, the body’s cells become increasingly less responsive to insulin (increased insulin resistance) and beta cells in the pancreas produce less and less insulin (called beta-cell burnout). In fact, when people are diagnosed with type 2 diabetes, they usually have already lost up to 50% or more of their beta cell function. As type 2 diabetes progresses, people typically need to add one or more different types of medications. The good news is that there are many more choices available for treatments, and a number of these medications don’t cause as much hypoglycemia, hunger and/or weight gain (e.g., metformin, pioglitazone, DPP-4 inhibitors, GLP-1 agonists, SGLT-2 inhibitors, and better insulin). Diligent management early on can help preserve remaining beta cell function and sometimes slow progression of the disease, although the need to use more and different types of medications does not mean that you have failed.
Diabetes experts feel that these blood glucose monitoring devices give patients a significant amount of independence to manage their disease process; and they are a great tool for education as well. It is also important to remember that these devices can be used intermittently with fingerstick measurements. For example, a well-controlled patient with diabetes can rely on fingerstick glucose checks a few times a day and do well. If they become ill, if they decide to embark on a new exercise regimen, if they change their diet and so on, they can use the sensor to supplement their fingerstick regimen, providing more information on how they are responding to new lifestyle changes or stressors. This kind of system takes us one step closer to closing the loop, and to the development of an artificial pancreas that senses insulin requirements based on glucose levels and the body's needs and releases insulin accordingly - the ultimate goal.
Jump up ^ Sattar N, Preiss D, Murray HM, Welsh P, Buckley BM, de Craen AJ, Seshasai SR, McMurray JJ, Freeman DJ, Jukema JW, Macfarlane PW, Packard CJ, Stott DJ, Westendorp RG, Shepherd J, Davis BR, Pressel SL, Marchioli R, Marfisi RM, Maggioni AP, Tavazzi L, Tognoni G, Kjekshus J, Pedersen TR, Cook TJ, Gotto AM, Clearfield MB, Downs JR, Nakamura H, Ohashi Y, Mizuno K, Ray KK, Ford I (February 2010). "Statins and risk of incident diabetes: a collaborative meta-analysis of randomised statin trials". Lancet. 375 (9716): 735–42. doi:10.1016/S0140-6736(09)61965-6. PMID 20167359.
People with diabetes either don't make insulin or their body's cells no longer are able to use the insulin, leading to high blood sugars. By definition, diabetes is having a blood glucose level of greater than or equal to126 milligrams per deciliter (mg/dL) after an 8-hour fast (not eating anything), or by having a non-fasting glucose level greater than or equal to 200 mg/dL along with symptoms of diabetes, or a glucose level of greater than or equal to 200 mg/dL on a 2-hour glucose tolerance test, or an A1C greater than or equal to 6.5%. Unless the person is having obvious symptoms of diabetes or is in a diabetic crisis, the diagnosis must be confirmed with a repeat test.