Hyperglycemia (ie, random blood glucose concentration of more than 200 mg/dL or 11 mmol/L) results when insulin deficiency leads to uninhibited gluconeogenesis and prevents the use and storage of circulating glucose. The kidneys cannot reabsorb the excess glucose load, causing glycosuria, osmotic diuresis, thirst, and dehydration. Increased fat and protein breakdown leads to ketone production and weight loss. Without insulin, a child with type 1 diabetes mellitus wastes away and eventually dies due to DKA. The effects of insulin deficiency are shown in the image below.

Then, once you do have an injury, uncontrolled diabetes can make it harder for your body to heal. “High blood sugars provide a good environment for bacteria to grow,” she says. That's because diabetes is also often accompanied by high blood pressure and high cholesterol, and the resulting plaque buildup can narrow blood vessels, reducing blood supply and leading to slow healing.
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.
Diabetic retinopathy is a leading cause of blindness and visual disability. Diabetes mellitus is associated with damage to the small blood vessels in the retina, resulting in loss of vision. Findings, consistent from study to study, make it possible to suggest that, after 15 years of diabetes, approximately 2% of people become blind, while about 10% develop severe visual handicap. Loss of vision due to certain types of glaucoma and cataract may also be more common in people with diabetes than in those without the disease.
Although urine can also be tested for the presence of glucose, checking urine is not a good way to monitor treatment or adjust therapy. Urine testing can be misleading because the amount of glucose in the urine may not reflect the current level of glucose in the blood. Blood glucose levels can get very low or reasonably high without any change in the glucose levels in the urine.

Type 2 diabetes is believed to have a strong genetic link, meaning that it tends to run in families. Several genes are being studied that may be related to the cause of type 2 diabetes. If you have any of the following type 2 diabetes risk factors, it’s important to ask your doctor about a diabetes test. With a proper diabetes diet and healthy lifestyle habits, along with diabetes medication, if necessary, you can manage type 2 diabetes just like you manage other areas of your life. Be sure to continue seeking the latest information on type 2 diabetes as you become your own health advocate.
Does having type 2 diabetes affect life expectancy? While continued improvements in therapies and care for type 2 diabetes may be helping patients live longer, the unfortunate reality is that type 2 diabetes has been shown to decrease life expectancy by up to ten years, according to Diabetes UK. There is still much to be done to ensure that all patients have access to appropriate healthcare and treatments to live a happier and healthier life with type 2 diabetes.
If you are at increased risk of diabetes, have symptoms of diabetes, or have pre-diabetes (a major warning sign for diabetes), your doctor will check to see if you have diabetes. Your doctor may also check to see if you have diabetes if you are over the age of 45, have a family history of the disease, are overweight, or if you are at increased risk for another reason. The tests used to check for diabetes are the same tests used to check for pre-diabetes.
Poor vision, limited manual dexterity due to arthritis, tremor, or stroke, or other physical limitations may make monitoring blood glucose levels more difficult for older people. However, special monitors are available. Some have large numerical displays that are easier to read. Some provide audible instructions and results. Some monitors read blood glucose levels through the skin and do not require a blood sample. People can consult a diabetes educator to determine which meter is most appropriate.
At the same time that the body is trying to get rid of glucose from the blood, the cells are starving for glucose and sending signals to the body to eat more food, thus making patients extremely hungry. To provide energy for the starving cells, the body also tries to convert fats and proteins to glucose. The breakdown of fats and proteins for energy causes acid compounds called ketones to form in the blood. Ketones also will be excreted in the urine. As ketones build up in the blood, a condition called ketoacidosis can occur. This condition can be life threatening if left untreated, leading to coma and death.
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]

Retinopathy: If blood sugar levels are too high, they can damage the eyes and cause vision loss and blindness. Retinopathy causes the development and leaking of new blood vessels behind the eye. Other effects of diabetes, such as high blood pressure and high cholesterol, can make this worse. According to the CDC, early treatment can prevent or reduce the risk of blindness in an estimated 90 percent of people with diabetes.
Rates of diabetes in 1985 were estimated at 30 million, increasing to 135 million in 1995 and 217 million in 2005.[18] This increase is believed to be primarily due to the global population aging, a decrease in exercise, and increasing rates of obesity.[18] The five countries with the greatest number of people with diabetes as of 2000 are India having 31.7 million, China 20.8 million, the United States 17.7 million, Indonesia 8.4 million, and Japan 6.8 million.[109] It is recognized as a global epidemic by the World Health Organization.[1]
Other potentially important mechanisms associated with type 2 diabetes and insulin resistance include: increased breakdown of lipids within fat cells, resistance to and lack of incretin, high glucagon levels in the blood, increased retention of salt and water by the kidneys, and inappropriate regulation of metabolism by the central nervous system.[10] However, not all people with insulin resistance develop diabetes, since an impairment of insulin secretion by pancreatic beta cells is also required.[13]

There is evidence that certain emotions can promote type 2 diabetes. A recent study found that depression seems to predispose people to diabetes. Other research has tied emotional stress to diabetes, though the link hasn't been proved. Researchers speculate that the emotional connection may have to do with the hormone cortisol, which floods the body during periods of stress. Cortisol sends glucose to the blood, where it can fuel a fight-or-flight response, but overuse of this system may lead to dysfunction.

How does high blood sugar (hyperglycemia) feel? To maintain the right amount of blood sugar, the body needs insulin, a hormone that delivers this sugar to the cells. When insulin is lacking, blood sugar builds up. We describe symptoms of high blood sugar, including fatigue, weight loss, and frequent urination. Learn who is at risk and when to see a doctor here. Read now
People with diabetes aim for a hemoglobin A1C level of less than 7%. Achieving this level is difficult, but the lower the hemoglobin A1C level, the less likely people are to have complications. Doctors may recommend a slightly higher or lower target for certain people depending on their particular health situation. However, levels above 9% show poor control, and levels above 12% show very poor control. Most doctors who specialize in diabetes care recommend that hemoglobin A1C be measured every 3 to 6 months.

Type 2 DM is primarily due to lifestyle factors and genetics.[45] 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.[16] 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.[11] Even those who are not obese often have a high waist–hip ratio.[11]

FIGURE 19-1 ■. This figure shows the hyperbolic relationship of insulin resistance and beta cell function. On the y-axis is beta cell function as reflected in the first-phase insulin response during intravenous (IV) glucose infusion; on the x-axis is insulin sensitivity and its mirror image resistance. In a subject with normal glucose tolerance (NGT) and beta-cell reserve, an increase in insulin resistance results in increased insulin release and normal glucose tolerance. In an individual for whom the capacity to increase insulin release is compromised, increasing insulin resistance with partial or no beta-cell compensation results in progression from normal glucose tolerance, to impaired glucose tolerance (IGT), and finally to diabetes (T2D). Differences between these categories are small at high insulin sensitivity, which may be maintained by weight reduction, exercise, and certain drugs. At a critical degree of insulin resistance, due to obesity or other listed factors, only a further small increment in resistance requires a large increase in insulin output. Those that can increase insulin secretion to this extent retain normal glucose tolerance; those who cannot achieve this degree of insulin secretion (e.g., due to a mild defect in genes regulating insulin synthesis, insulin secretion, insulin action, or an ongoing immune destruction of beta cells) now unmask varying degrees of carbohydrate intolerance. The product of insulin sensitivity (the reciprocal of insulin resistance) and acute insulin response (a measurement beta-cell function) has been called the “disposition index.” This index remains constant in an individual with normal beta cell compensation in response to changes in insulin resistance. IGT, impaired glucose tolerance; NGT, normal glucose tolerance; T2D, type 2 diabetes.

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.
Large, population-based studies in China, Finland and USA have recently demonstrated the feasibility of preventing, or delaying, the onset of diabetes in overweight subjects with mild glucose intolerance (IGT). The studies suggest that even moderate reduction in weight and only half an hour of walking each day reduced the incidence of diabetes by more than one half.
Another dipstick test can determine the presence of protein or albumin in the urine. Protein in the urine can indicate problems with kidney function and can be used to track the development of renal failure. A more sensitive test for urine protein uses radioactively tagged chemicals to detect microalbuminuria, small amounts of protein in the urine, that may not show up on dipstick tests.

Jump up ^ Seida, Jennifer C.; Mitri, Joanna; Colmers, Isabelle N.; Majumdar, Sumit R.; Davidson, Mayer B.; Edwards, Alun L.; Hanley, David A.; Pittas, Anastassios G.; Tjosvold, Lisa; Johnson, Jeffrey A. (Oct 2014). "Effect of Vitamin D3 Supplementation on Improving Glucose Homeostasis and Preventing Diabetes: A Systematic Review and Meta-Analysis". The Journal of Clinical Endocrinology & Metabolism. 99 (10): 3551–60. doi:10.1210/jc.2014-2136. PMC 4483466. PMID 25062463.

Diabetes mellitus is linked with an increased risk of heart attacks, strokes, poor blood circulation to the legs and damage to the eyes, feet and kidneys. Early diagnosis and strict control of blood sugar, blood pressure and cholesterol levels can help to prevent or delay these complications associated with diabetes. Maintaining a healthy lifestyle (regular exercise, eating healthily and maintaining a healthy weight) is important in reducing the risk of developing type 2 diabetes.
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
A healthy lifestyle can prevent almost all cases of type 2 diabetes. A large research study called the Diabetes Prevention Program, found that patients who made intensive changes including diet and exercise, reduced their risk of developing diabetes by 58%. Patients who were over 60 years old seemed to experience extra benefit; they reduced their risk by 71%. In comparison, patients who were given the drug metformin for prevention only reduced their risk by 31%.

And remember not to let others scare you into thinking the worst. Getting educated will help you to understand that a diabetes diagnosis, while serious, is not the end of the world. For some people, lifestyle modifications such as weight loss, healthy eating, and exercise can actually get blood sugars below the diabetes threshold. You can control your diabetes and not let it control you.
People with full-blown type 2 diabetes are not able to use the hormone insulin properly, and have what’s called insulin resistance. Insulin is necessary for glucose, or sugar, to get from your blood into your cells to be used for energy. When there is not enough insulin — or when the hormone doesn’t function as it should — glucose accumulates in the blood instead of being used by the cells. This sugar accumulation may lead to the aforementioned complications.