The body’s immune system is responsible for fighting off foreign invaders, like harmful viruses and bacteria. In people with type 1 diabetes, the immune system mistakes the body’s own healthy cells for foreign invaders. The immune system attacks and destroys the insulin-producing beta cells in the pancreas. After these beta cells are destroyed, the body is unable to produce insulin.

Clinical Manifestations. Diabetes mellitus can present a wide variety of symptoms, from none at all to profound ketosis and coma. If the disease manifests itself late in life, patients may not know they have it until it is discovered during a routine examination, or when the symptoms of chronic vascular disease, insidious renal failure, or impaired vision cause them to seek medical help.


One of the most common ways people with type 2 diabetes attempt to lower their blood sugar is by drastically reducing their intake of carbs. The ADA agrees that carbohydrate counting is essential if you have diabetes, but extreme diets like the ketogenic diet, which reduces carb intake to as little as 5 percent of your daily calories, can be risky for some people with diabetes. (36)
FASTING GLUCOSE TEST. Blood is drawn from a vein in the patient's arm after a period at least eight hours when the patient has not eaten, usually in the morning before breakfast. The red blood cells are separated from the sample and the amount of glucose is measured in the remaining plasma. A plasma level of 7.8 mmol/L (200 mg/L) or greater can indicate diabetes. The fasting glucose test is usually repeated on another day to confirm the results.
Type 2 diabetes primarily occurs as a result of obesity and lack of exercise.[1] Some people are more genetically at risk than others.[6] Type 2 diabetes makes up about 90% of cases of diabetes, with the other 10% due primarily to diabetes mellitus type 1 and gestational diabetes.[1] In diabetes mellitus type 1 there is a lower total level of insulin to control blood glucose, due to an autoimmune induced loss of insulin-producing beta cells in the pancreas.[12][13] Diagnosis of diabetes is by blood tests such as fasting plasma glucose, oral glucose tolerance test, or glycated hemoglobin (A1C).[3]

All types of diabetes mellitus have something in common. Normally, your body breaks down the sugars and carbohydrates you eat into a special sugar called glucose. Glucose fuels the cells in your body. But the cells need insulin, a hormone, in your bloodstream in order to take in the glucose and use it for energy. With diabetes mellitus, either your body doesn't make enough insulin, it can't use the insulin it does produce, or a combination of both.
If sugars in general are not associated with increased diabetes risk, but sodas are, it suggests the possibility that something other than sugar explains this relationship.16 Sodas are often accompanied by cheeseburgers, chicken nuggets, and other unhealthful foods. That is, soda consumption can be a sign of a diet focusing on fast foods or an overall unhealthful diet and lifestyle. And sugary snack foods (e.g., cookies and snack pastries) are often high in fat; the sugar lures us in to the fat calories hiding inside. Some, but not all, observational trials have sought to control for these confounding variables. 
Type 2 diabetes can be prevented with lifestyle changes. People who are overweight and lose as little as 7 percent of their body weight and who increase physical activity (for example, walking 30 minutes per day) can decrease their risk of diabetes mellitus by more than 50%. Metformin and acarbose, drugs that are used to treat diabetes, may reduce the risk of diabetes in people with impaired glucose regulation.
Normally, blood glucose levels are tightly controlled by insulin, a hormone produced by the pancreas. Insulin lowers the blood glucose level. When the blood glucose elevates (for example, after eating food), insulin is released from the pancreas to normalize the glucose level by promoting the uptake of glucose into body cells. In patients with diabetes, the absence of insufficient production of or lack of response to insulin causes hyperglycemia. Diabetes is a chronic medical condition, meaning that although it can be controlled, it lasts a lifetime.

Doctors and people with diabetes have observed that infections seem more common if you have diabetes. Research in this area, however, has not proved whether this is entirely true, nor why. It may be that high levels of blood sugar impair your body's natural healing process and your ability to fight infections. For women, bladder and vaginal infections are especially common.
An article published in November 2012 in the journal Global Public Health found that countries with more access to HFCS tended to have higher rates of the disease. Though it’s likely that these countries’ overall eating habits play a role in their populations’ diabetes risk, a study published in February 2013 in the journal PLoS One found limiting access to HFCS in particular may help reduce rates of the diagnosis.
In type 1 diabetes, other symptoms to watch for include unexplained weight loss, lethargy, drowsiness, and hunger. Symptoms sometimes occur after a viral illness. In some cases, a person may reach the point of diabetic ketoacidosis (DKA) before a type 1 diagnosis is made. DKA occurs when blood glucose is dangerously high and the body can't get nutrients into the cells because of the absence of insulin. The body then breaks down muscle and fat for energy, causing an accumulation of ketones in the blood and urine. Symptoms of DKA include a fruity odor on the breath; heavy, taxed breathing; and vomiting. If left untreated, DKA can result in stupor, unconsciousness, and even death.

Low blood sugar (hypoglycemia), is common in people with type 1 and type 2 DM. Most cases are mild and are not considered medical emergencies. Effects can range from feelings of unease, sweating, trembling, and increased appetite in mild cases to more serious effects such as confusion, changes in behavior such as aggressiveness, seizures, unconsciousness, and (rarely) permanent brain damage or death in severe cases.[24][25] Moderately low blood sugar may easily be mistaken for drunkenness;[26] rapid breathing and sweating, cold, pale skin are characteristic of low blood sugar but not definitive.[27] Mild to moderate cases are self-treated by eating or drinking something high in sugar. Severe cases can lead to unconsciousness and must be treated with intravenous glucose or injections with glucagon.[28]
A healthy meal plan for people with diabetes is generally the same as healthy eating for anyone – low in saturated fat, moderate in salt and sugar, with meals based on lean protein, non-starchy vegetables, whole grains, healthy fats, and fruit. Foods that say they are healthier for people with diabetes generally offer no special benefit. Most of them still raise blood glucose levels, are more expensive, and can also have a laxative effect if they contain sugar alcohols.
Most cases of diabetes involve many genes, with each being a small contributor to an increased probability of becoming a type 2 diabetic.[10] If one identical twin has diabetes, the chance of the other developing diabetes within his lifetime is greater than 90%, while the rate for nonidentical siblings is 25–50%.[13] As of 2011, more than 36 genes had been found that contribute to the risk of type 2 diabetes.[37] All of these genes together still only account for 10% of the total heritable component of the disease.[37] The TCF7L2 allele, for example, increases the risk of developing diabetes by 1.5 times and is the greatest risk of the common genetic variants.[13] Most of the genes linked to diabetes are involved in beta cell functions.[13]
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.
Finally, modern society should probably shoulder at least some of the blame for the type 2 diabetes epidemic. Access to cheap, calorie-laden foods may even influence type 2 risk beyond simply their effects on body weight; the stuff that is in processed foods, like high-fructose corn syrup, could alter the body's chemistry or gut microbes in a way that affects health. Add to that the fact that most Americans are sedentary, spending their time sitting in cubicles, driving in cars, playing video games, or watching television. The lack of exercise, plus the abundance of unhealthy foods, cultivates a fertile breeding ground for diabetes.
Insulin, a hormone released from the pancreas (an organ behind the stomach that also produces digestive enzymes), controls the amount of glucose in the blood. Glucose in the bloodstream stimulates the pancreas to produce insulin. Insulin helps glucose to move from the blood into the cells. Once inside the cells, glucose is converted to energy, which is used immediately, or the glucose is stored as fat or glycogen until it is needed.
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.
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