This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

Gestational diabetes mellitus (GDM) resembles type 2 DM in several respects, involving a combination of relatively inadequate insulin secretion and responsiveness. It occurs in about 2–10% of all pregnancies and may improve or disappear after delivery.[50] However, after pregnancy approximately 5–10% of women with GDM are found to have DM, most commonly type 2.[50] GDM is fully treatable, but requires careful medical supervision throughout the pregnancy. Management may include dietary changes, blood glucose monitoring, and in some cases, insulin may be required.

Symptoms of type 1 diabetes can start quickly, in a matter of weeks. Symptoms of type 2 diabetes often develop slowly—over the course of several years—and can be so mild that you might not even notice them. Many people with type 2 diabetes have no symptoms. Some people do not find out they have the disease until they have diabetes-related health problems, such as blurred vision or heart trouble.


Culturally appropriate education may help people with type 2 diabetes control their blood sugar levels, for up to 24 months.[89] If changes in lifestyle in those with mild diabetes has not resulted in improved blood sugars within six weeks, medications should then be considered.[23] There is not enough evidence to determine if lifestyle interventions affect mortality in those who already have DM2.[62]

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]
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.
Healthy lifestyle choices can help you prevent type 2 diabetes. Even if you have diabetes in your family, diet and exercise can help you prevent the disease. If you've already received a diagnosis of diabetes, you can use healthy lifestyle choices to help prevent complications. And if you have prediabetes, lifestyle changes can slow or halt the progression from prediabetes to diabetes.

In people with type 1 diabetes, the symptoms often begin abruptly and dramatically. A serious condition called diabetic ketoacidosis, a complication in which the body produces excess acid, may quickly develop. In addition to the usual diabetes symptoms of excessive thirst and urination, the initial symptoms of diabetic ketoacidosis also include nausea, vomiting, fatigue, and—particularly in children—abdominal pain. Breathing tends to become deep and rapid as the body attempts to correct the blood’s acidity (see Acidosis), and the breath smells fruity and like nail polish remover. Without treatment, diabetic ketoacidosis can progress to coma and death, sometimes very quickly.
Pay attention if you find yourself feeling drowsy or lethargic; pain or numbness in your extremities; vision changes; fruity or sweet-smelling breath which is one of the symptoms of high ketones; and experiencing nausea or vomiting—as these are additional signs that something is not right. If there’s any question, see your doctor immediately to ensure that your blood sugar levels are safe and rule out diabetes.
Diabetes that's triggered by pregnancy is called gestational diabetes (pregnancy, to some degree, leads to insulin resistance). It is often diagnosed in middle or late pregnancy. Because high blood sugar levels in a mother are circulated through the placenta to the baby, gestational diabetes must be controlled to protect the baby's growth and development.
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.

To explain what hemoglobin A1c is, think in simple terms. Sugar sticks, and when it's around for a long time, it's harder to get it off. In the body, sugar sticks too, particularly to proteins. The red blood cells that circulate in the body live for about three months before they die off. When sugar sticks to these hemoglobin proteins in these cells, it is known as glycosylated hemoglobin or hemoglobin A1c (HBA1c). Measurement of HBA1c gives us an idea of how much sugar is present in the bloodstream for the preceding three months. In most labs, the normal range is 4%-5.9 %. In poorly controlled diabetes, its 8.0% or above, and in well controlled patients it's less than 7.0% (optimal is <6.5%). The benefits of measuring A1c is that is gives a more reasonable and stable view of what's happening over the course of time (three months), and the value does not vary as much as finger stick blood sugar measurements. There is a direct correlation between A1c levels and average blood sugar levels as follows.
Elevated homocysteine levels in the blood called hyperhomocysteinemia, is a sign that the body isn't producing enough of the amino acid homocysteine. is a rare and serious condition that may be inherited (genetic). People with homocystinuria die at an early age. Symptoms of hyperhomocysteinemia include developmental delays, osteoporosis, blood clots, heart attack, heart disease, stroke, and visual abnormalities.
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.
*MDVIP respects your privacy and will only use your personal information as stated in our Privacy Policy and Terms of Use. By providing your number, you are giving your express written consent to receive telemarketing calls or text messages using an automatic phone dialing system or an artificial or prerecorded voice at that number. You can contact us at any time if you wish to stop receiving such messages.
Type 2 diabetes is different. A person with type 2 diabetes still produces insulin but the body doesn't respond to it normally. Glucose is less able to enter the cells and do its job of supplying energy (a problem called insulin resistance). This raises the blood sugar level, so the pancreas works hard to make even more insulin. Eventually, this strain can make the pancreas unable to produce enough insulin to keep blood sugar levels normal.
Inhalable insulin has been developed.[125] The original products were withdrawn due to side effects.[125] Afrezza, under development by the pharmaceuticals company MannKind Corporation, was approved by the United States Food and Drug Administration (FDA) for general sale in June 2014.[126] An advantage to inhaled insulin is that it may be more convenient and easy to use.[127]

Diabetes is a condition in which the body cannot properly store and use fuel for energy. The body's main fuel is a form of sugar called glucose, which comes from food (after it has been broken down). Glucose enters the blood and is used by cells for energy. To use glucose, the body needs a hormone called insulin that's made by the pancreas. Insulin is important because it allows glucose to leave the blood and enter the body's cells.


It is important to record blood glucose readings taken at different times of the day – after fasting (before breakfast) as well as 2 hours after a meal. This allows your doctor to see a snapshot of how your blood glucose levels vary during the day and to recommend treatments accordingly. Most blood glucose meters now have "memory" that stores a number of blood glucose tests along with the time and date they were taken. Some even allow for graphs and charts of the results to be created and sent to your phone.
Some cases of diabetes are caused by the body's tissue receptors not responding to insulin (even when insulin levels are normal, which is what separates it from type 2 diabetes); this form is very uncommon. Genetic mutations (autosomal or mitochondrial) can lead to defects in beta cell function. Abnormal insulin action may also have been genetically determined in some cases. Any disease that causes extensive damage to the pancreas may lead to diabetes (for example, chronic pancreatitis and cystic fibrosis). Diseases associated with excessive secretion of insulin-antagonistic hormones can cause diabetes (which is typically resolved once the hormone excess is removed). Many drugs impair insulin secretion and some toxins damage pancreatic beta cells. The ICD-10 (1992) diagnostic entity, malnutrition-related diabetes mellitus (MRDM or MMDM, ICD-10 code E12), was deprecated by the World Health Organization (WHO) when the current taxonomy was introduced in 1999.[53]
A second theory, dubbed the hygiene hypothesis, blames the rise of type 1 on a society that's too clean. Good housekeeping and hygiene habits mean far fewer interactions with germs, which in turn may foster an immune system prone to going awry. "In a developing country, you have more infectious disease. This is associated with a lower risk of type 1 diabetes," says Li Wen, MD, PhD, an immunologist at the Yale University School of Medicine. In her lab, rodents raised in hyper-clean environments are more likely to get type 1 than those reared in dirtier cages.
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Also striking are the differences in incidence between mainland Italy (8.4 cases per 100,000 population) and the Island of Sardinia (36.9 cases per 100,000 population). These variations strongly support the importance of environmental factors in the development of type 1 diabetes mellitus. Most countries report that incidence rates have at least doubled in the last 20 years. Incidence appears to increase with distance from the equator. [31]
Diabetes mellitus is a chronic disease for which there is treatment but no known cure.  Treatment is aimed at keeping blood glucose levels as close to normal as possible.  This is achieved with a combination of diet, exercise and insulin or oral medication.  People with type 1 diabetes need to be hospitalized right after they are diagnosed to get their glucose levels down to an acceptable level.
Insulin is only recommended for individuals for type 2 diabetics when they have not been able to get blood sugars low enough to prevent complications through other means. To avoid insulin, those with this health condition should work very hard to follow a healthy eating plan that includes a lot of vegetables and lean proteins, exercise every day, and keep stress in perspective. They also should take their oral drugs regularly. It can be difficult to follow these recommendations and the help of your doctor, nutritionist, diabetes educator, health coach, or integrative medicine practitioner may be helpful. If you who want to avoid taking medicine, work with health professionals who are knowledgeable about lifestyle medicine, and can help you understand how to fit the changes into your life.
Excessive thirst typically goes hand-in-hand with increased urination. As your body pulls water out of the tissues to dilute your blood and to rid your body of sugar through the urine, the urge to drink increases. Many people describe this thirst as an unquenchable one. To stay hydrated, you drink excessive amounts of liquids. And if those liquids contain simple sugars (soda, sweet iced tea, lemonade, or juice, for example) your sugars will skyrocket even higher.

Type 2 diabetes is a progressive, chronic disease related to your body's challenges with regulating blood sugar. It is often associated with generalized inflammation. Your pancreas produces the hormone insulin to convert sugar (glucose) to energy that you either use immediately or store. With type 2 diabetes, you are unable to use that insulin efficiently. Although your body produces the hormone, either there isn't enough of it to keep up with the amount of glucose in your system, or the insulin being produced isn't being used as well as it should be, both of which result in high blood sugar levels.

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 (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 levels of glucose in the blood vary normally throughout the day. They rise after a meal and return to pre-meal levels within about 2 hours after eating. Once the levels of glucose in the blood return to premeal levels, insulin production decreases. The variation in blood glucose levels is usually within a narrow range, about 70 to 110 milligrams per deciliter (mg/dL) of blood in healthy people. If people eat a large amount of carbohydrates, the levels may increase more. People older than 65 years tend to have slightly higher levels, especially after eating.
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.
If you recognize any of the symptoms, contact your doctor immediately. A simple in-office test for sugar in the urine is used for diagnosis. If that test is positive, then a drop of blood from the fingertip will confirm diabetes. Every day, thousands of adults and children around the world are diagnosed, but many go undetected. Early diagnosis cannot prevent Type 1, but it can head off potentially devastating, even fatal, health concerns.
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]
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.
While poor vision is hardly uncommon—more than 60 percent of the American population wears glasses or contacts, after all—sudden changes in your vision, especially blurriness, need to be addressed by your doctor. Blurry vision is often a symptom of diabetes, as high blood sugar levels can cause swelling in the lenses of your eye, distorting your sight in the process. Fortunately, for many people, the effect is temporary and goes away when their blood sugar is being managed.
Merck & Co., Inc., Kenilworth, NJ, USA is a global healthcare leader working to help the world be well. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. The Merck Manual was first published in 1899 as a service to the community. The legacy of this great resource continues as the Merck Manual in the US and Canada and the MSD Manual outside of North America. Learn more about our commitment to Global Medical Knowledge.

Impaired glucose tolerance (IGT) and impaired fasting glycaemia (IFG) refer to levels of blood glucose concentration above the normal range, but below those which are diagnostic for diabetes. Subjects with IGT and/or IFG are at substantially higher risk of developing diabetes and cardiovascular disease than those with normal glucose tolerance. The benefits of clinical intervention in subjects with moderate glucose intolerance is a topic of much current interest.
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
ORAL GLUCOSE TOLERANCE TEST. Blood samples are taken from a vein before and after a patient drinks a thick, sweet syrup of glucose and other sugars. In a non-diabetic, the level of glucose in the blood goes up immediately after the drink and then decreases gradually as insulin is used by the body to metabolize, or absorb, the sugar. In a diabetic, the glucose in the blood goes up and stays high after drinking the sweetened liquid. A plasma glucose level of 11.1 mmol/L (200 mg/dL) or higher at two hours after drinking the syrup and at one other point during the two-hour test period confirms the diagnosis of diabetes.
People with glucose levels between normal and diabetic have impaired glucose tolerance (IGT) or insulin resistance. People with impaired glucose tolerance do not have diabetes, but are at high risk for progressing to diabetes. Each year, 1% to 5% of people whose test results show impaired glucose tolerance actually eventually develop diabetes. Weight loss and exercise may help people with impaired glucose tolerance return their glucose levels to normal. In addition, some physicians advocate the use of medications, such as metformin (Glucophage), to help prevent/delay the onset of overt diabetes.

The WHO estimates that diabetes mellitus resulted in 1.5 million deaths in 2012, making it the 8th leading cause of death.[9][101] However another 2.2 million deaths worldwide were attributable to high blood glucose and the increased risks of cardiovascular disease and other associated complications (e.g. kidney failure), which often lead to premature death and are often listed as the underlying cause on death certificates rather than diabetes.[101][104] For example, in 2014, the International Diabetes Federation (IDF) estimated that diabetes resulted in 4.9 million deaths worldwide,[19] using modeling to estimate the total number of deaths that could be directly or indirectly attributed to diabetes.[20]
The amount of glucose in the bloodstream is tightly regulated by insulin and other hormones. Insulin is always being released in small amounts by the pancreas. When the amount of glucose in the blood rises to a certain level, the pancreas will release more insulin to push more glucose into the cells. This causes the glucose levels in the blood (blood glucose levels) to drop.

Jump up ^ Ahlqvist, Emma; Storm, Petter; Käräjämäki, Annemari; Martinell, Mats; Dorkhan, Mozhgan; Carlsson, Annelie; Vikman, Petter; Prasad, Rashmi B; Aly, Dina Mansour (2018). "Novel subgroups of adult-onset diabetes and their association with outcomes: a data-driven cluster analysis of six variables". The Lancet Diabetes & Endocrinology. 0 (5): 361–369. doi:10.1016/S2213-8587(18)30051-2. ISSN 2213-8587. PMID 29503172.
Type 2 diabetes is a preventable disease that affects more than 9 percent of the U.S. population, or about 29 million people. According to the Centers for Disease Control and Prevention, more than a quarter — some 8 million people — remain undiagnosed. With complications including nerve damage, kidney damage, poor blood circulation, and even death, it’s important for us all to know the early signs of type 2 diabetes.
×