Diabetes mellitus type 2 (also known as type 2 diabetes) is a long-term metabolic disorder that is characterized by high blood sugar, insulin resistance, and relative lack of insulin.[6] Common symptoms include increased thirst, frequent urination, and unexplained weight loss.[3] Symptoms may also include increased hunger, feeling tired, and sores that do not heal.[3] Often symptoms come on slowly.[6] Long-term complications from high blood sugar include heart disease, strokes, diabetic retinopathy which can result in blindness, kidney failure, and poor blood flow in the limbs which may lead to amputations.[1] The sudden onset of hyperosmolar hyperglycemic state may occur; however, ketoacidosis is uncommon.[4][5]
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. Blood glucose is your main source of energy and comes from the food you eat. Insulin, a hormone made by the pancreas, helps glucose from food get into your cells to be used for energy. Sometimes your body doesn’t make enough—or any—insulin or doesn’t use insulin well. Glucose then stays in your blood and doesn’t reach your cells.

Type 2 diabetes used to be called adult-onset diabetes or non-insulin dependent diabetes because it was diagnosed mainly in adults who did not require insulin to manage their condition. However, because more children are starting to be diagnosed with T2D, and insulin is used more frequently to help manage type 2 diabetes, referring to the condition as “adult-onset” or “non-insulin dependent” is no longer accurate.
Gestational diabetes. Gestational diabetes is a type of diabetes that happens only during pregnancy. Gestational diabetes can cause health problems for the baby and the mother if not controlled. Although gestational diabetes goes away after your baby is born, having diabetes during pregnancy raises your risk for type 2 diabetes later on.2 Learn more about gestational diabetes at the National Diabetes Information Clearinghouse.
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.[111] It is recognized as a global epidemic by the World Health Organization.[1]
Evidence linking hepatic insulin sensitivity to intraorgan triglyceride content has been steadily accumulating. In insulin-treated type 2 diabetes, insulin dose correlates with the extent of fatty liver (35), and in turn, this is associated with insulin sensitivity to suppression of hepatic glucose production (36). Decreasing the fat content of liver is associated with improvement in insulin suppression of glucose production and, thereby, with improvement in fasting plasma glucose (20,23).

Prevention and treatment involve maintaining a healthy diet, regular physical exercise, a normal body weight, and avoiding use of tobacco.[2] Control of blood pressure and maintaining proper foot care are important for people with the disease.[2] Type 1 DM must be managed with insulin injections.[2] Type 2 DM may be treated with medications with or without insulin.[12] Insulin and some oral medications can cause low blood sugar.[13] Weight loss surgery in those with obesity is sometimes an effective measure in those with type 2 DM.[14] Gestational diabetes usually resolves after the birth of the baby.[15]
Prevention and treatment involve maintaining a healthy diet, regular physical exercise, a normal body weight, and avoiding use of tobacco.[2] Control of blood pressure and maintaining proper foot care are important for people with the disease.[2] Type 1 DM must be managed with insulin injections.[2] Type 2 DM may be treated with medications with or without insulin.[12] Insulin and some oral medications can cause low blood sugar.[13] Weight loss surgery in those with obesity is sometimes an effective measure in those with type 2 DM.[14] Gestational diabetes usually resolves after the birth of the baby.[15]

People with diabetes can benefit from education about the disease and treatment, good nutrition to achieve a normal body weight, and exercise, with the goal of keeping both short-term and long-term blood glucose levels within acceptable bounds. In addition, given the associated higher risks of cardiovascular disease, lifestyle modifications are recommended to control blood pressure.[80][81]
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]
If the amount of insulin available is insufficient, or if cells respond poorly to the effects of insulin (insulin insensitivity or insulin resistance), or if the insulin itself is defective, then glucose is not absorbed properly by the body cells that require it, and is not stored appropriately in the liver and muscles. The net effect is persistently high levels of blood glucose, poor protein synthesis, and other metabolic derangements, such as acidosis.[59]
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^ 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.
Intensive blood sugar lowering (HbA1c<6%) as opposed to standard blood sugar lowering (HbA1c of 7–7.9%) does not appear to change mortality.[76][77] The goal of treatment is typically an HbA1c of 7 to 8% or a fasting glucose of less than 7.2 mmol/L (130 mg/dl); however these goals may be changed after professional clinical consultation, taking into account particular risks of hypoglycemia and life expectancy.[60][78][79] Despite guidelines recommending that intensive blood sugar control be based on balancing immediate harms with long-term benefits, many people – for example people with a life expectancy of less than nine years who will not benefit, are over-treated.[80]

Diabetes mellitus occurs throughout the world but is more common (especially type 2) in more developed countries. The greatest increase in rates has however been seen in low- and middle-income countries,[101] where more than 80% of diabetic deaths occur.[105] The fastest prevalence increase is expected to occur in Asia and Africa, where most people with diabetes will probably live in 2030.[106] The increase in rates in developing countries follows the trend of urbanization and lifestyle changes, including increasingly sedentary lifestyles, less physically demanding work and the global nutrition transition, marked by increased intake of foods that are high energy-dense but nutrient-poor (often high in sugar and saturated fats, sometimes referred to as the "Western-style" diet).[101][106] The global number of diabetes cases might increase by 48% between 2017 and 2045.[8]
Fuchsberger C, Flannick J, Teslovich TM, Mahajan A, Agarwala V, Gaulton KJ, Ma C, Fontanillas P, Moutsianas L, McCarthy DJ, Rivas MA, Perry JRB, Sim X, Blackwell TW, Robertson NR, Rayner NW, Cingolani P, Locke AE, Tajes JF, Highland HM, Dupuis J, Chines PS, Lindgren CM, Hartl C, Jackson AU, Chen H, Huyghe JR, van de Bunt M, Pearson RD, Kumar A, Müller-Nurasyid M, Grarup N, Stringham HM, Gamazon ER, Lee J, Chen Y, Scott RA, Below JE, Chen P, Huang J, Go MJ, Stitzel ML, Pasko D, Parker SCJ, Varga TV, Green T, Beer NL, Day-Williams AG, Ferreira T, Fingerlin T, Horikoshi M, Hu C, Huh I, Ikram MK, Kim BJ, Kim Y, Kim YJ, Kwon MS, Lee J, Lee S, Lin KH, Maxwell TJ, Nagai Y, Wang X, Welch RP, Yoon J, Zhang W, Barzilai N, Voight BF, Han BG, Jenkinson CP, Kuulasmaa T, Kuusisto J, Manning A, Ng MCY, Palmer ND, Balkau B, Stančáková A, Abboud HE, Boeing H, Giedraitis V, Prabhakaran D, Gottesman O, Scott J, Carey J, Kwan P, Grant G, Smith JD, Neale BM, Purcell S, Butterworth AS, Howson JMM, Lee HM, Lu Y, Kwak SH, Zhao W, Danesh J, Lam VKL, Park KS, Saleheen D, So WY, Tam CHT, Afzal U, Aguilar D, Arya R, Aung T, Chan E, Navarro C, Cheng CY, Palli D, Correa A, Curran JE, Rybin D, Farook VS, Fowler SP, Freedman BI, Griswold M, Hale DE, Hicks PJ, Khor CC, Kumar S, Lehne B, Thuillier D, Lim WY, Liu J, van der Schouw YT, Loh M, Musani SK, Puppala S, Scott WR, Yengo L, Tan ST, Taylor HA Jr, Thameem F, Wilson G Sr, Wong TY, Njølstad PR, Levy JC, Mangino M, Bonnycastle LL, Schwarzmayr T, Fadista J, Surdulescu GL, Herder C, Groves CJ, Wieland T, Bork-Jensen J, Brandslund I, Christensen C, Koistinen HA, Doney ASF, Kinnunen L, Esko T, Farmer AJ, Hakaste L, Hodgkiss D, Kravic J, Lyssenko V, Hollensted M, Jørgensen ME, Jørgensen T, Ladenvall C, Justesen JM, Käräjämäki A, Kriebel J, Rathmann W, Lannfelt L, Lauritzen T, Narisu N, Linneberg A, Melander O, Milani L, Neville M, Orho-Melander M, Qi L, Qi Q, Roden M, Rolandsson O, Swift A, Rosengren AH, Stirrups K, Wood AR, Mihailov E, Blancher C, Carneiro MO, Maguire J, Poplin R, Shakir K, Fennell T, DePristo M, de Angelis MH, Deloukas P, Gjesing AP, Jun G, Nilsson P, Murphy J, Onofrio R, Thorand B, Hansen T, Meisinger C, Hu FB, Isomaa B, Karpe F, Liang L, Peters A, Huth C, O'Rahilly SP, Palmer CNA, Pedersen O, Rauramaa R, Tuomilehto J, Salomaa V, Watanabe RM, Syvänen AC, Bergman RN, Bharadwaj D, Bottinger EP, Cho YS, Chandak GR, Chan JCN, Chia KS, Daly MJ, Ebrahim SB, Langenberg C, Elliott P, Jablonski KA, Lehman DM, Jia W, Ma RCW, Pollin TI, Sandhu M, Tandon N, Froguel P, Barroso I, Teo YY, Zeggini E, Loos RJF, Small KS, Ried JS, DeFronzo RA, Grallert H, Glaser B, Metspalu A, Wareham NJ, Walker M, Banks E, Gieger C, Ingelsson E, Im HK, Illig T, Franks PW, Buck G, Trakalo J, Buck D, Prokopenko I, Mägi R, Lind L, Farjoun Y, Owen KR, Gloyn AL, Strauch K, Tuomi T, Kooner JS, Lee JY, Park T, Donnelly P, Morris AD, Hattersley AT, Bowden DW, Collins FS, Atzmon G, Chambers JC, Spector TD, Laakso M, Strom TM, Bell GI, Blangero J, Duggirala R, Tai ES, McVean G, Hanis CL, Wilson JG, Seielstad M, Frayling TM, Meigs JB, Cox NJ, Sladek R, Lander ES, Gabriel S, Burtt NP, Mohlke KL, Meitinger T, Groop L, Abecasis G, Florez JC, Scott LJ, Morris AP, Kang HM, Boehnke M, Altshuler D, McCarthy MI. The genetic architecture of type 2 diabetes. Nature. 2016 Aug 4;536(7614):41-47. doi: 10.1038/nature18642. Epub 2016 Jul 11.
Type 2 DM begins with insulin resistance, a condition in which cells fail to respond to insulin properly.[2] As the disease progresses, a lack of insulin may also develop.[11] This form was previously referred to as "non insulin-dependent diabetes mellitus" (NIDDM) or "adult-onset diabetes".[2] The most common cause is a combination of excessive body weight and insufficient exercise.[2]
No major organization recommends universal screening for diabetes as there is no evidence that such a program improve outcomes.[55][56] Screening is recommended by the United States Preventive Services Task Force (USPSTF) in adults without symptoms whose blood pressure is greater than 135/80 mmHg.[57] For those whose blood pressure is less, the evidence is insufficient to recommend for or against screening.[57] There is no evidence that it changes the risk of death in this group of people.[56] They also recommend screening among those who are overweight and between the ages of 40 and 70.[58]
Several vision complications can result from type 2 diabetes, from glaucoma to cataracts to the most common, diabetic retinopathy. Over time, high blood sugar levels can damage the blood vessels in the eyes, Sullivan says. If left untreated, diabetic retinopathy can cause severe vision loss and even blindness. Nearly half of everyone diagnosed with diabetes has some degree of diabetic retinopathy, according to the National Eye Institute.
At present, the American Diabetes Association does not recommend general screening of the population for type 1 diabetes, though screening of high risk individuals, such as those with a first degree relative (sibling or parent) with type 1 diabetes should be encouraged. Type 1 diabetes tends to occur in young, lean individuals, usually before 30 years of age; however, older patients do present with this form of diabetes on occasion. This subgroup is referred to as latent autoimmune diabetes in adults (LADA). LADA is a slow, progressive form of type 1 diabetes. Of all the people with diabetes, only approximately 10% have type 1 diabetes and the remaining 90% have type 2 diabetes.
There are a number of rare cases of diabetes that arise due to an abnormality in a single gene (known as monogenic forms of diabetes or "other specific types of diabetes").[10][13] These include maturity onset diabetes of the young (MODY), Donohue syndrome, and Rabson–Mendenhall syndrome, among others.[10] Maturity onset diabetes of the young constitute 1–5% of all cases of diabetes in young people.[39]
Type 2 diabetes was also previously referred to as non-insulin dependent diabetes mellitus (NIDDM), or adult-onset diabetes mellitus (AODM). In type 2 diabetes, patients can still produce insulin, but do so relatively inadequately for their body's needs, particularly in the face of insulin resistance as discussed above. In many cases this actually means the pancreas produces larger than normal quantities of insulin. A major feature of type 2 diabetes is a lack of sensitivity to insulin by the cells of the body (particularly fat and muscle cells).

Blood travels throughout your body, and when too much glucose (sugar) is present, it disrupts the normal environment that the organ systems of your body function within. In turn, your body starts to exhibit signs that things are not working properly inside—those are the symptoms of diabetes people sometimes experience. If this problem—caused by a variety of factors—is left untreated, it can lead to a number of damaging complications such as heart attacks, strokes, blindness, kidney failure, and blood vessel disease that may require an amputation, nerve damage, and impotence in men.
Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. Blood glucose is your main source of energy and comes from the food you eat. Insulin, a hormone made by the pancreas, helps glucose from food get into your cells to be used for energy. Sometimes your body doesn’t make enough—or any—insulin or doesn’t use insulin well. Glucose then stays in your blood and doesn’t reach your cells.
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