The glucose level at which symptoms develop varies greatly from individual to individual (and from time to time in the same individual), depending in part on the duration of diabetes, the frequency of hypoglycemic episodes, the rate of fall of glycemia, and overall control. (Glucose is also the sole energy source for erythrocytes and the kidney medulla.)
diabetes mel´litus 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 may be 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. Insulin resistance may also sometimes play a role in the etiology of diabetes. 

American Diabetes Association Joslin Diabetes Center Mayo Clinic International Diabetes Federation Canadian Diabetes Association National Institute of Diabetes and Digestive and Kidney Diseases Diabetes Daily American Heart Association Diabetes Forecast Diabetic Living American Association of Clinical Endocrinologists European Association for the Study of Diabetes
Older people may have a difficult time adding exercise to their daily life, particularly if they have not been active or if they have a disorder that limits their movement, such as arthritis. However, they may be able to add exercise to their usual routine. For example, they can walk instead of drive or climb the stairs instead of take the elevator. Also, many community organizations offer exercise programs designed for older people.

Exposure to certain viral infections (mumps and Coxsackie viruses) or other environmental toxins may serve to trigger abnormal antibody responses that cause damage to the pancreas cells where insulin is made. Some of the antibodies seen in type 1 diabetes include anti-islet cell antibodies, anti-insulin antibodies and anti-glutamic decarboxylase antibodies. These antibodies can be detected in the majority of patients, and may help determine which individuals are at risk for developing type 1 diabetes.
This depends on the type of diabetes. Type 2 diabetes, and to a lesser extent type 1 diabetes, may run in families. If a parent has diabetes, their children will not necessarily get it but they are at an increased risk. In type 2 diabetes, lifestyle factors such as being overweight (obesity) and lack of exercise can significantly increase your risk of developing diabetes. Some rarer types of diabetes mellitus may be inherited.

The United Kingdom Prospective Diabetes Study (UKPDS) was a clinical study conducted by Z that was published in The Lancet in 1998. Around 3,800 people with type 2 diabetes were followed for an average of ten years, and were treated with tight glucose control or the standard of care, and again the treatment arm had far better outcomes. This confirmed the importance of tight glucose control, as well as blood pressure control, for people with this condition.[86][132][133]
If you’re getting a good night’s rest but still find yourself so tired you can barely function, it’s definitely worth mentioning to your doctor. Diabetes often wreaks havoc on a person’s normal blood sugar levels, causing fatigue in the process. In later stages, the tissue death associated with untreated diabetes can also limit circulation, meaning oxygenated blood isn’t being effectively transported to your vital organs, making your body work harder and tiring you out along the way.
Manage mild hypoglycemia by giving rapidly absorbed oral carbohydrate or glucose; for a comatose patient, administer an intramuscular injection of the hormone glucagon, which stimulates the release of liver glycogen and releases glucose into the circulation. Where appropriate, an alternative therapy is intravenous glucose (preferably no more than a 10% glucose solution). All treatments for hypoglycemia provide recovery in approximately 10 minutes. (See Treatment.)
Several other signs and symptoms can mark the onset of diabetes although they are not specific to the disease. In addition to the known ones above, they include blurred vision, headache, fatigue, slow healing of cuts, and itchy skin. Prolonged high blood glucose can cause glucose absorption in the lens of the eye, which leads to changes in its shape, resulting in vision changes. Long-term vision loss can also be caused by diabetic retinopathy. A number of skin rashes that can occur in diabetes are collectively known as diabetic dermadromes.[23]
This is specific to type 2 diabetes. It occurs when insulin is produced normally in the pancreas, but the body is still unable move glucose into the cells for fuel. At first, the pancreas will create more insulin to overcome the body’s resistance. Eventually the cells “wear out.” At that point the body slows insulin production, leaving too much glucose in the blood. This is known as prediabetes. A person with prediabetes has a blood sugar level higher than normal but not high enough for a diagnosis of diabetes. Unless tested, the person may not be aware, as there are no clear symptoms. Type 2 diabetes occurs as insulin production continues to decrease and resistance increases.

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.
American Diabetes Association Joslin Diabetes Center Mayo Clinic International Diabetes Federation Canadian Diabetes Association National Institute of Diabetes and Digestive and Kidney Diseases Diabetes Daily American Heart Association Diabetes Forecast Diabetic Living American Association of Clinical Endocrinologists European Association for the Study of Diabetes

It is especially important that persons with diabetes who are taking insulin not skip meals; they must also be sure to eat the prescribed amounts at the prescribed times during the day. Since the insulin-dependent diabetic needs to match food consumption to the available insulin, it is advantageous to increase the number of daily feedings by adding snacks between meals and at bedtime.
For people who want to avoid drugs, taking an aggressive approach to healthy eating plan and lifestyle change is an option. It isn't easy, but if someone is very committed and motivated, lifestyle changes can be enough to maintain a healthy blood sugar level and to lose weight. Learning about a healthy diabetes diet (a low glycemic load diet) can be an good place to start.

By the time a person is diagnosed with type 2 diabetes, up to 50% of the beta cells in the pancreas have usually been damaged. In fact, these cells may have been declining for up to 10 years before the diagnosis. Along with raised blood pressure and elevated cholesterol levels, this predisposes the person to arterial damage years before diabetes is diagnosed. So, at the time of diagnosis, the person is already at risk for cardiovascular disease (CVD).
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]
What does the research say about proactive type 2 diabetes management? Research shows that proactive management can pay off in fewer complications down the road. In the landmark UKPDS study, 5,102 patients newly diagnosed with type 2 diabetes were followed for an average of 10 years to determine whether intensive use of blood glucose-lowering drugs would result in health benefits. Tighter average glucose control (an A1c of 7.0% vs. an A1c of 7.9%) reduced the rate of complications in the eyes, kidneys, and nervous system, by 25%. For every percentage point decrease in A1c (e.g., from 9% to 8%), there was a 25% reduction in diabetes-related deaths, and an 18% reduction in combined fatal and nonfatal heart attacks.
So what determines where fat is stored, and thus a person's propensity for insulin resistance and type 2 diabetes? Well, just having more fat in the body increases the risk that some of it will get misplaced. But exercise may also have a role in fat placement. Exercise is known to reduce insulin resistance; one way it may do this is by burning fat out of the muscle. Because of this, getting enough exercise may stave off type 2 in some cases. Genes may also help orchestrate the distribution of fat in the body, which illustrates how lifestyle and genetics interact.
Morbidity and mortality stem from the metabolic derangements and from the long-term complications that affect small and large vessels, resulting in retinopathy, nephropathy, neuropathy, ischemic heart disease, and arterial obstruction with gangrene of extremities.2 The acute clinical manifestations can be fully understood in the context of current knowledge of the secretion and action of insulin.3 Genetic and other etiologic considerations implicate autoimmune mechanisms in the evolution of the most common form of childhood diabetes, known as type 1a diabetes.4,5 Genetic defects in insulin secretion are increasingly recognized and understood as defining the causes of monogenic forms of diabetes such as maturity-onset diabetes of youth (MODY) and neonatal DM and contributing to the spectrum of T2DM.6
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.  
Diabetic ketoacidosis can be caused by infections, stress, or trauma, all of which may increase insulin requirements. In addition, missing doses of insulin is also an obvious risk factor for developing diabetic ketoacidosis. Urgent treatment of diabetic ketoacidosis involves the intravenous administration of fluid, electrolytes, and insulin, usually in a hospital intensive care unit. Dehydration can be very severe, and it is not unusual to need to replace 6-7 liters of fluid when a person presents in diabetic ketoacidosis. Antibiotics are given for infections. With treatment, abnormal blood sugar levels, ketone production, acidosis, and dehydration can be reversed rapidly, and patients can recover remarkably well.

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.
Diabetes is one of the first diseases described[21] with an Egyptian manuscript from c. 1500 BCE mentioning "too great emptying of the urine."[110] The first described cases are believed to be of type 1 diabetes.[110] Indian physicians around the same time identified the disease and classified it as madhumeha or honey urine noting that the urine would attract ants.[110] The term "diabetes" or "to pass through" was first used in 230 BCE by the Greek Apollonius Of Memphis.[110] The disease was rare during the time of the Roman empire with Galen commenting that he had only seen two cases during his career.[110]
Get to Know Your Medications: If you have diabetes, it is important to know and understand what your medications do. This can help to keep blood sugars controlled and prevent low and high blood sugars. Certain medicines need to be taken with food, or they will cause your blood sugar will drop. There are so many diabetes medications out there. Being your own advocate can help you. Make sure to tell your doctor if your medications are too expensive or if they are causing any side effects. If your medication regimen is not working for you, odds are your doctor can find a new medicine that might work better.
About 84 million adults in the US (more than 1 out of 3) have prediabetes, and about 90% do not know they have it until a routine blood test is ordered, or symptoms of type 2 diabetes develop. For example, excessive thirst, frequent urination, and unexplained weight loss. If you have prediabetes also it puts you at risk for heart attack, stroke, and type 2 diabetes.