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.
Type 2 diabetes usually begins with insulin resistance, a condition in which muscle, liver, and fat cells do not use insulin well. As a result, your body needs more insulin to help glucose enter cells. At first, the pancreas makes more insulin to keep up with the added demand. Over time, the pancreas can’t make enough insulin, and blood glucose levels rise.
Though not routinely used any longer, the oral glucose tolerance test (OGTT) is a gold standard for making the diagnosis of type 2 diabetes. It is still commonly used for diagnosing gestational diabetes and in conditions of pre-diabetes, such as polycystic ovary syndrome. With an oral glucose tolerance test, the person fasts overnight (at least eight but not more than 16 hours). Then first, the fasting plasma glucose is tested. After this test, the person receives an oral dose (75 grams) of glucose. There are several methods employed by obstetricians to do this test, but the one described here is standard. Usually, the glucose is in a sweet-tasting liquid that the person drinks. Blood samples are taken at specific intervals to measure the blood glucose.
Complications of diabetes are responsible for considerable morbidity and mortality. The acute complications of diabetes are hypo- and hyperglycemic coma and infections. The chronic complications include microvascular complications such as retinopathy and nephropathy, and the macrovascular complications of heart disease and stroke. Diabetes mellitus is the commonest cause of blindness and renal failure in the UK and the USA. Other common complications include autonomic and peripheral neuropathy. A combination of vascular and neuropathic disturbances results in a high prevalence of impotence in men with diabetes. Peripheral neuropathy causes lack of sensation in the feet which can cause minor injuries to go unnoticed, become infected and, with circulatory problems obstructing healing, ulceration and gangrene are serious risks and amputation is not uncommon. Evidence from meta-analysis of studies of the relationship between glycemic control and microvascular complications (Wang, Lau, & Chalmers, 1993), and from the longitudinal multicenter Diabetes Control and Complications Trial (DCCT) in the USA (DCCT Research Group, 1993), have established a clear relationship between improved blood glucose control and reduction of risk of retinopathy and other microvascular complications in insulin-dependent diabetes mellitus (IDDM). It is likely that there would be similar findings for noninsulin-dependent diabetes mellitus (NIDDM) though the studies did not include NIDDM patients. However, the DCCT included highly selected, well-motivated, well-educated and well-supported patients, cared for by well-staffed diabetes care teams involving educators and psychologists as well as diabetologists and diabetes specialist nurses.

Often people don't experience symptoms of diabetes until their blood sugars are very high. Symptoms of diabetes include: increased thirst, increased urination, increased hunger, extreme fatigues, numbness and tingling in the extremities (hands and feet), cuts and wounds that are slow to heal, and blurred vision. Some people also experience other less common symptoms including weight loss, dry itchy skin, increased yeast infections, erectile dysfunction, and acanthosis nigricans (thick, "velvety" patches found in the folds or creases of skin, such as the neck, that is indicative of insulin resistance).


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.)

Blood sugar should be regularly monitored so that any problems can be detected and treated early. Treatment involves lifestyle changes such as eating a healthy and balanced diet and regular physical exercise. If lifestyle changes alone are not enough to regulate the blood glucose level, anti-diabetic medication in the form of tablets or injections may be prescribed. In some cases, people who have had type 2 diabetes for many years are eventually prescribed insulin injections.
Doctors can also measure the level of a protein, hemoglobin A1C (also called glycosylated or glycolated hemoglobin), in the blood. Hemoglobin is the red, oxygen-carrying substance in red blood cells. When blood is exposed to high blood glucose levels over a period of time, glucose attaches to the hemoglobin and forms glycosylated hemoglobin. The hemoglobin A1C level (reported as the percentage of hemoglobin that is A1C) reflects long-term trends in blood glucose levels rather than rapid changes.
Patients with Type I diabetes need daily injections of insulin to help their bodies use glucose. The amount and type of insulin required depends on the height, weight, age, food intake, and activity level of the individual diabetic patient. Some patients with Type II diabetes may need to use insulin injections if their diabetes cannot be controlled with diet, exercise, and oral medication. Injections are given subcutaneously, that is, just under the skin, using a small needle and syringe. Injection sites can be anywhere on the body where there is looser skin, including the upper arm, abdomen, or upper thigh.
As of 2015, an estimated 415 million people had diabetes worldwide,[8] with type 2 DM making up about 90% of the cases.[16][17] This represents 8.3% of the adult population,[17] with equal rates in both women and men.[18] As of 2014, trends suggested the rate would continue to rise.[19] Diabetes at least doubles a person's risk of early death.[2] From 2012 to 2015, approximately 1.5 to 5.0 million deaths each year resulted from diabetes.[8][9] The global economic cost of diabetes in 2014 was estimated to be US$612 billion.[20] In the United States, diabetes cost $245 billion in 2012.[21]
Insulin Therapy. Exogenous insulin is given to patients with diabetes mellitus as a supplement to the insufficient amount of endogenous insulin that they produce. In some cases, this must make up for an absolute lack of insulin from the pancreas. Exogenous insulin is available in various types. It must be given by injection, usually subcutaneously, and because it is a potent drug, the dosage must be measured meticulously. Commonly, regular insulin, which is a fast-acting insulin with a short span of action, is mixed with one of the longer-acting insulins and both types are administered in one injection.

The primary complications of diabetes due to damage in small blood vessels include damage to the eyes, kidneys, and nerves.[32] Damage to the eyes, known as diabetic retinopathy, is caused by damage to the blood vessels in the retina of the eye, and can result in gradual vision loss and eventual blindness.[32] Diabetes also increases the risk of having glaucoma, cataracts, and other eye problems. It is recommended that diabetics visit an eye doctor once a year.[33] Damage to the kidneys, known as diabetic nephropathy, can lead to tissue scarring, urine protein loss, and eventually chronic kidney disease, sometimes requiring dialysis or kidney transplantation.[32] Damage to the nerves of the body, known as diabetic neuropathy, is the most common complication of diabetes.[32] The symptoms can include numbness, tingling, pain, and altered pain sensation, which can lead to damage to the skin. Diabetes-related foot problems (such as diabetic foot ulcers) may occur, and can be difficult to treat, occasionally requiring amputation. Additionally, proximal diabetic neuropathy causes painful muscle atrophy and weakness.
gestational diabetes diabetes mellitus with onset or first recognition during pregnancy, usually during the second or third trimester. In some cases mild, undetected glucose intolerance was present before pregnancy. It often disappears after the end of the pregnancy, but many women with this condition develop permanent diabetes mellitus in later life. Although the disordered carbohydrate metabolism is usually mild, prompt detection and treatment are necessary to avoid fetal and neonatal morbidity and mortality.
Insulin-dependent diabetes mellitus is believed to result from autoimmune, environmental, and/or genetic factors. Whatever the cause, the end result is destruction of insulin-producing pancreatic beta cells, a dramatic decrease in the secretion of insulin, and hyperglycemia. Non-insulin-dependent diabetes mellitus is presumably heterogeneous in origin. It is associated with older age, obesity, a family history of diabetes, and ethnicity (genetic components). The vast majority of those with non-insulin-dependent diabetes are overweight Kahn (2003). This form of the disorder has a much slower rate of progression than insulin-dependent diabetes. Over time the ability to respond to insulin decreases, resulting in increased levels of blood glucose. The pancreatic secretion of insulin increases in an attempt to compensate for the elevated levels of glucose. If the condition is untreated, the pancreatic production of insulin decreases and may even cease.
Dietary factors also influence the risk of developing type 2 DM. Consumption of sugar-sweetened drinks in excess is associated with an increased risk.[46][47] The type of fats in the diet is also important, with saturated fat and trans fats increasing the risk and polyunsaturated and monounsaturated fat decreasing the risk.[45] Eating lots of white rice, and other starches, also may increase the risk of diabetes.[48] A lack of physical activity is believed to cause 7% of cases.[49]
Diabetes mellitus (DM) is a strong predictor of cardiovascular morbidity and mortality and is associated with both micro- and macrovascular complications.1 Cardiovascular disease (CVD) causes up to 70% of all deaths in people with DM. The epidemic of DM will thus be followed by a burden of diabetes-related vascular diseases. The number of DM patients increases with aging of the population, in part because of the increasing prevalence of obesity and sedentary lifestyle. Although the mortality from coronary artery disease (CAD) in patients without DM has declined since the 1990s, the mortality in men with type 2 diabetes (T2DM) has not changed significantly.2 Moreover, DM is an independent risk factor for heart failure. Heart failure is closely related to diabetic cardiomyopathy: changes in the structure and function of the myocardium are not directly linked to CAD or hypertension. Diabetic cardiomyopathy is clinically characterized by an initial increase in left ventricular stiffness and subclinical diastolic dysfunction, gradually compromising left ventricular systolic function with loss of contractile function and progress into overt congestive heart failure. DM accounts for a significant percentage of patients with a diagnosis of heart failure in epidemiologic studies such as the Framingham Study and the UK Prospective Diabetes Study (UKPDS).2 A 1% increase in glycated hemoglobin (HbA1c) correlates to an increment of 8% in heart failure.3 The prevalence of heart failure in elderly diabetic patients is up to 30%.3
Unlike many health conditions, diabetes is managed mostly by you, with support from your health care team (including your primary care doctor, foot doctor, dentist, eye doctor, registered dietitian nutritionist, diabetes educator, and pharmacist), family, and other important people in your life. Managing diabetes can be challenging, but everything you do to improve your health is worth it!
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.

Over recent decades, and particularly in the past five years, researchers have found dozens of genes with links to diabetes. The count stands at about 50 genes for type 1 and 38 for type 2. The numbers have risen quickly in recent years because of advances in the gene-sequencing technology used to conduct genome-wide association studies. This technique involves taking the genetic compositions of a group of people with a disease and comparing them en masse to the genomes of people who don't have the disease.


There are some interesting developments in blood glucose monitoring including continuous glucose sensors. The new continuous glucose sensor systems involve an implantable cannula placed just under the skin in the abdomen or in the arm. This cannula allows for frequent sampling of blood glucose levels. Attached to this is a transmitter that sends the data to a pager-like device. This device has a visual screen that allows the wearer to see, not only the current glucose reading, but also the graphic trends. In some devices, the rate of change of blood sugar is also shown. There are alarms for low and high sugar levels. Certain models will alarm if the rate of change indicates the wearer is at risk for dropping or rising blood glucose too rapidly. One version is specifically designed to interface with their insulin pumps. In most cases the patient still must manually approve any insulin dose (the pump cannot blindly respond to the glucose information it receives, it can only give a calculated suggestion as to whether the wearer should give insulin, and if so, how much). However, in 2013 the US FDA approved the first artificial pancreas type device, meaning an implanted sensor and pump combination that stops insulin delivery when glucose levels reach a certain low point. All of these devices need to be correlated to fingersticks measurements for a few hours before they can function independently. The devices can then provide readings for 3 to 5 days.
A type 2 diabetes diet or a type 2 diabetic diet is important for blood sugar (glucose) control in people with diabetes to prevent complications of diabetes. There are a variety of type 2 diabetes diet eating plans such as the Mediterranean diet, Paleo diet, ADA Diabetes Diet, and vegetarian diets.Learn about low and high glycemic index foods, what foods to eat, and what foods to avoid if you have type 2 diabetes.
Onset of type 2 diabetes can be delayed or prevented through proper nutrition and regular exercise.[60][61] Intensive lifestyle measures may reduce the risk by over half.[24][62] The benefit of exercise occurs regardless of the person's initial weight or subsequent weight loss.[63] High levels of physical activity reduce the risk of diabetes by about 28%.[64] Evidence for the benefit of dietary changes alone, however, is limited,[65] with some evidence for a diet high in green leafy vegetables[66] and some for limiting the intake of sugary drinks.[32] In those with impaired glucose tolerance, diet and exercise either alone or in combination with metformin or acarbose may decrease the risk of developing diabetes.[24][67] Lifestyle interventions are more effective than metformin.[24] A 2017 review found that, long term, lifestyle changes decreased the risk by 28%, while medication does not reduce risk after withdrawal.[68] While low vitamin D levels are associated with an increased risk of diabetes, correcting the levels by supplementing vitamin D3 does not improve that risk.[69]
Some people with type 2 diabetes are treated with insulin. Insulin is either injected with a syringe several times per day, or delivered via an insulin pump. The goal of insulin therapy is to mimic the way the pancreas would produce and distribute its own insulin, if it were able to manufacture it. Taking insulin does not mean you have done a bad job of trying to control your blood glucose—instead it simply means that your body doesn’t produce or use enough of it on its own to cover the foods you eat.
Insulin Therapy. Exogenous insulin is given to patients with diabetes mellitus as a supplement to the insufficient amount of endogenous insulin that they produce. In some cases, this must make up for an absolute lack of insulin from the pancreas. Exogenous insulin is available in various types. It must be given by injection, usually subcutaneously, and because it is a potent drug, the dosage must be measured meticulously. Commonly, regular insulin, which is a fast-acting insulin with a short span of action, is mixed with one of the longer-acting insulins and both types are administered in one injection.

Diabetes mellitus (DM) comprises a group of disorders characterized by hyperglycemia. It is the sixth leading cause of death in the United States and results in $132 billion in total direct and indirect costs. Although the incidence of Type 1 diabetes has doubled over the past 30 years, the increase in Type 2 diabetes has been even more dramatic. An estimated 20–40% of cases in large pediatric diabetes centers are now Type 2, and the rates are expected to rise along with the epidemic of childhood and adolescent obesity (Chapter 11).
The problem with sugar, regardless of type, is the sheer amount of it that’s found in the Standard American Diet (SAD), which is the typical eating plan many people in the United States — as well as those in an increasing number of modernized countries — have developed a taste for. When consumed in excess, foods in this category can lead to heart disease, stroke, and other serious health issues. “Often, foods with added sugar also contain fat,” explains Grieger, noting that these components go hand in hand when it comes to the risk for insulin resistance, the hallmark of type 2 diabetes.
The patient, physician, nurse, and dietician must carefully evaluate the patient's life style, nutritional needs, and ability to comply with the proposed dietary prescription. There are a variety of meal planning systems that can be used by the patient with diabetes; each has benefits and drawbacks that need to be evaluated in order to maximize compliance. Two of the most frequently used ones are the exchange system (see accompanying table) and the carbohydrate counting system.
Diet, exercise, and education are the cornerstones of treatment of diabetes and often the first recommendations for people with mild diabetes. Weight loss is important for people who are overweight. People who continue to have elevated blood glucose levels despite lifestyle changes, or have very high blood glucose levels and people with type 1 diabetes (no matter their blood glucose levels) also require drugs.
Over recent decades, and particularly in the past five years, researchers have found dozens of genes with links to diabetes. The count stands at about 50 genes for type 1 and 38 for type 2. The numbers have risen quickly in recent years because of advances in the gene-sequencing technology used to conduct genome-wide association studies. This technique involves taking the genetic compositions of a group of people with a disease and comparing them en masse to the genomes of people who don't have the disease.
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]
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]
Insulin is a hormone produced by the beta cells within the pancreas in response to the intake of food. The role of insulin is to lower blood sugar (glucose) levels by allowing cells in the muscle, liver and fat to take up sugar from the bloodstream that has been absorbed from food, and store it away as energy. In type 1 diabetes (previously called insulin-dependent diabetes mellitus), the insulin-producing cells are destroyed and the body is not able to produce insulin naturally. This means that sugar is not stored away but is constantly released from energy stores giving rise to high sugar levels in the blood. This in turn causes dehydration and thirst (because the high glucose ‘spills over’ into the urine and pulls water out of the body at the same time). To exacerbate the problem, because the body is not making insulin it ‘thinks’ that it is starving so does everything it can to release even more stores of energy into the bloodstream. So, if left untreated, patients become increasingly unwell, lose weight, and develop a condition called diabetic ketoacidosis, which is due to the excessive release of acidic energy stores and causes severe changes to how energy is used and stored in the body.
Some people who have type 2 diabetes can achieve their target blood sugar levels with diet and exercise alone, but many also need diabetes medications or insulin therapy. The decision about which medications are best depends on many factors, including your blood sugar level and any other health problems you have. Your doctor might even combine drugs from different classes to help you control your blood sugar in several different ways.
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.
What you need to know about borderline diabetes Borderline diabetes, known as prediabetes, is a condition where blood sugar levels are higher than normal but not yet high enough to be type 2 diabetes. This MNT Knowledge Center article explains the signs to look out for, how to monitor the disease, and ways to prevent it becoming full diabetes. Read now
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