If genetics has taught us anything about diabetes, it's that, for most people, genes aren't the whole story. True, a few rare kinds of diabetes—including those collectively called MODY for maturity-onset diabetes of the young—have been traced to defects in a single gene. But for other types of diabetes, hereditary factors are still not well understood.
The most common cause of acquired blindness in many developed nations, diabetic retinopathy is rare in the prepubertal child or within 5 years of onset of diabetes. The prevalence and severity of retinopathy increase with age and are greatest in patients whose diabetic control is poor.  Prevalence rates seem to be declining, yet an estimated 80% of people with type 1 diabetes mellitus develop retinopathy. 
Persons with diabetes who take insulin must be careful about indulging in unplanned exercise. Strenuous physical activity can rapidly lower their blood sugar and precipitate a hypoglycemic reaction. For a person whose blood glucose level is over 250 mg/dl, the advice would be not to exercise at all. At this range, the levels of insulin are too low and the body would have difficulty transporting glucose into exercising muscles. The result of exercise would be a rise in blood glucose levels.
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.
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.
Rosiglitazone, a thiazolidinedione, has not been found to improve long-term outcomes even though it improves blood sugar levels. Additionally it is associated with increased rates of heart disease and death. Angiotensin-converting enzyme inhibitors (ACEIs) prevent kidney disease and improve outcomes in those with diabetes. The similar medications angiotensin receptor blockers (ARBs) do not. A 2016 review recommended treating to a systolic blood pressure of 140 to 150 mmHg.
Damage to small blood vessels can affect the eyes, kidneys, and nerves. Damage to eyes, specifically the retina, is called diabetic retinopathy and is the leading cause of blindness. Damage to the kidneys, called diabetic nephropathy, can lead to kidney failure and the need for dialysis. Damage to the nerves that supply the legs and arms and gastrointestinal tract is called diabetic neuropathy. Some people with diabetes who develop peripheral neuropathy (damage to the nerves in the legs) and have poor blood flow to the legs may eventually need an amputation.
In type 2 diabetes, there also is a steady decline of beta cells that adds to the process of elevated blood sugars. Essentially, if someone is resistant to insulin, the body can, to some degree, increase production of insulin and overcome the level of resistance. After time, if production decreases and insulin cannot be released as vigorously, hyperglycemia develops.
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.
In 2013, of the estimated 382 million people with diabetes globally, more than 80 per cent lived in LMIC. It was estimated that India had 65.1 million adults with diabetes in 2013, and had the 2nd position among the top 10 countries with the largest number of diabetes. This number is predicted to increase to 109 million by 2035 unless steps are taken to prevent new cases of diabetes1. Primary prevention of diabetes is feasible and strategies such as lifestyle modification are shown to be effective in populations of varied ethnicity2,3. However, for implementation of the strategies at the population level, national programmes which are culturally and socially acceptable and practical have to be formulated which are currently lacking in most of the developed and developing countries. Early diagnosis and institution of appropriate therapeutic measures yield the desired glycaemic outcomes and prevent the vascular complications4.
So what determines where fat is stored, and thus a person's propensity for insulin resistance and type 2 diabetes? Well, just having more fat in the body increases the risk that some of it will get misplaced. But exercise may also have a role in fat placement. Exercise is known to reduce insulin resistance; one way it may do this is by burning fat out of the muscle. Because of this, getting enough exercise may stave off type 2 in some cases. Genes may also help orchestrate the distribution of fat in the body, which illustrates how lifestyle and genetics interact.
Beta cells are vulnerable to more than just bad genes, which may explain the associations between type 2 diabetes and environmental factors that aren't related to how much fat a body has or where it is stored. Beta cells carry vitamin D receptors on their surface, and people with vitamin D deficiency are at increased risk for type 2. Plus, several studies have shown that people with higher levels of toxic substances in their blood—such as from the PCBs found in fish fat—are at increased risk of type 2 diabetes, though a cause-and-effect relationship hasn't been proved. (Toxic substances and vitamin D have also been implicated in type 1 diabetes, but the disease mechanism may be unrelated to what's going on in type 2.)
What are symptoms of type 2 diabetes in children? Type 2 diabetes is becoming increasingly common in children, and this is linked to a rise in obesity. However, the condition can be difficult to detect in children because it develops gradually. Symptoms, treatment, and prevention of type 2 diabetes are similar in children and adults. Learn more here. Read now
In type 2 diabetes (adult onset diabetes), the pancreas makes insulin, but it either doesn't produce enough, or the insulin does not work properly. Nine out of 10 people with diabetes have type 2. This type occurs most often in people who are over 40 years old but can occur even in childhood if there are risk factors present. Type 2 diabetes may sometimes be controlled with a combination of diet, weight management and exercise. However, treatment also may include oral glucose-lowering medications (taken by mouth) or insulin injections (shots).
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.
Clear evidence suggests a genetic component in type 1 diabetes mellitus. Monozygotic twins have a 60% lifetime concordance for developing type 1 diabetes mellitus, although only 30% do so within 10 years after the first twin is diagnosed. In contrast, dizygotic twins have only an 8% risk of concordance, which is similar to the risk among other siblings.
Education: People with diabetes should learn as much as possible about this condition and how to manage it. The more you know about your condition, the better prepared you are to manage it on a daily basis. Many hospitals offer diabetes education programs and many nurses and pharmacists have been certified to provide diabetes education. Contact a local hospital, doctor, or pharmacist to find out about programs and diabetes educators in your area.
The protocol for therapy is determined by the type of diabetes; patients with either type 1 or type 2 must pay attention to their diet and exercise regimens. Insulin therapy may be prescribed for patients with type 2 diabetes as well as any who are dependent on insulin. In most cases, the type 2 diabetes patient can be treated effectively by reducing caloric intake, maintaining target weight, and promoting physical exercise.
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.
The brain depends on glucose as a fuel. As glucose levels drop below 65 mg/dL (3.2 mmol/L) counterregulatory hormones (eg, glucagon, cortisol, epinephrine) are released, and symptoms of hypoglycemia develop. These symptoms include sweatiness, shaking, confusion, behavioral changes, and, eventually, coma when blood glucose levels fall below 30-40 mg/dL.
The relationship between type 2 diabetes and the main modifiable risk factors (excess weight, unhealthy diet, physical inactivity and tobacco use) is similar in all regions of the world. There is growing evidence that the underlying determinants of diabetes are a reflection of the major forces driving social, economic and cultural change: globalization, urbanization, population aging, and the general health policy environment.
Diabetes mellitus (DM) is best defined as a syndrome characterized by inappropriate fasting or postprandial hyperglycemia, caused by absolute or relative insulin deficiency and its metabolic consequences, which include disturbed metabolism of protein and fat. This syndrome results from a combination of deficiency of insulin secretion and its action. Diabetes mellitus occurs when the normal constant of the product of insulin secretion times insulin sensitivity, a parabolic function termed the “disposition index” (Figure 19-1), is inadequate to prevent hyperglycemia and its clinical consequences of polyuria, polydipsia, and weight loss. At high degrees of insulin sensitivity, small declines in the ability to secrete insulin cause only mild, clinically imperceptible defects in glucose metabolism. However, irrespective of insulin sensitivity, a minimum amount of insulin is necessary for normal metabolism. Thus, near absolute deficiency of insulin must result in severe metabolic disturbance as occurs in type 1 diabetes mellitus (T1DM). By contrast, with decreasing sensitivity to its action, higher amounts of insulin secretion are required for a normal disposition index. At a critical point in the disposition index curve (see Figure 19-1), a further small decrement in insulin sensitivity requires a large increase in insulin secretion; those who can mount these higher rates of insulin secretion retain normal glucose metabolism, whereas those who cannot increase their insulin secretion because of genetic or acquired defects now manifest clinical diabetes as occurs in type 2 diabetes (T2DM).
Hyperglycemic hyperosmolar nonketotic syndrome (HHNS). Signs and symptoms of this life-threatening condition include a blood sugar reading higher than 600 mg/dL (33.3 mmol/L), dry mouth, extreme thirst, fever greater than 101 F (38 C), drowsiness, confusion, vision loss, hallucinations and dark urine. Your blood sugar monitor may not be able to give you an exact reading at such high levels and may instead just read "high."
Type 2 diabetes primarily occurs as a result of obesity and lack of exercise. Some people are more genetically at risk than others. 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. 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. Diagnosis of diabetes is by blood tests such as fasting plasma glucose, oral glucose tolerance test, or glycated hemoglobin (A1C).
How does type 2 diabetes progress over time? Type 2 diabetes is a progressive disease, meaning that the body’s ability to regulate blood sugar gets worse over time, despite careful management. Over time, the body’s cells become increasingly less responsive to insulin (increased insulin resistance) and beta cells in the pancreas produce less and less insulin (called beta-cell burnout). In fact, when people are diagnosed with type 2 diabetes, they usually have already lost up to 50% or more of their beta cell function. As type 2 diabetes progresses, people typically need to add one or more different types of medications. The good news is that there are many more choices available for treatments, and a number of these medications don’t cause as much hypoglycemia, hunger and/or weight gain (e.g., metformin, pioglitazone, DPP-4 inhibitors, GLP-1 agonists, SGLT-2 inhibitors, and better insulin). Diligent management early on can help preserve remaining beta cell function and sometimes slow progression of the disease, although the need to use more and different types of medications does not mean that you have failed.
According to the National Institutes of Health, the reported rate of gestational diabetes is between 2% to 10% of pregnancies. Gestational diabetes usually resolves itself after pregnancy. Having gestational diabetes does, however, put mothers at risk for developing type 2 diabetes later in life. Up to 10% of women with gestational diabetes develop type 2 diabetes. It can occur anywhere from a few weeks after delivery to months or years later.
Excess glucose in the blood can damage small blood vessels in the nerves causing a tingling sensation or pain in the fingers, toes and limbs. Nerves that lie outside of the central nervous system may also be damaged, which is referred to as peripheral neuropathy. If nerves of the gastrointestinal tract are affected, this may cause vomiting, constipation and diarrhea.
Recently, battery-operated insulin pumps have been developed that can be programmed to mimic normal insulin secretion more closely. A person wearing an insulin pump still must monitor blood sugar several times a day and adjust the dosage, and not all diabetic patients are motivated or suited to such vigilance. It is hoped that in the future an implantable or external pump system may be perfected, containing a glucose sensor. In response to data from the sensor the pump will automatically deliver insulin according to changing levels of blood glucose.
Management of type 2 diabetes focuses on lifestyle interventions, lowering other cardiovascular risk factors, and maintaining blood glucose levels in the normal range. Self-monitoring of blood glucose for people with newly diagnosed type 2 diabetes may be used in combination with education, however the benefit of self monitoring in those not using multi-dose insulin is questionable. In those who do not want to measure blood levels, measuring urine levels may be done. Managing other cardiovascular risk factors, such as hypertension, high cholesterol, and microalbuminuria, improves a person's life expectancy. Decreasing the systolic blood pressure to less than 140 mmHg is associated with a lower risk of death and better outcomes. Intensive blood pressure management (less than 130/80 mmHg) as opposed to standard blood pressure management (less than 140-160 mmHg systolic to 85–100 mmHg diastolic) results in a slight decrease in stroke risk but no effect on overall risk of death.
Knowledge is power. A certified diabetes educator can provide you with diabetes self-management education. They specialize in diabetes and can help you learn about complicated or easier things. For example, they can help you set up your glucose meter, teach you about how your medicines work, or help you put together a meal plan. You can meet with them one on one or in group setting.
Type 1 diabetes occurs when your immune system, the body’s system for fighting infection, attacks and destroys the insulin-producing beta cells of the pancreas. Scientists think type 1 diabetes is caused by genes and environmental factors, such as viruses, that might trigger the disease. Studies such as TrialNet are working to pinpoint causes of type 1 diabetes and possible ways to prevent or slow the disease.
The classic oral glucose tolerance test measures blood glucose levels five times over a period of three hours. Some physicians simply get a baseline blood sample followed by a sample two hours after drinking the glucose solution. In a person without diabetes, the glucose levels rise and then fall quickly. In someone with diabetes, glucose levels rise higher than normal and fail to come back down as fast.
Diabetes mellitus is a disorder in which the amount of sugar in the blood is elevated. Doctors often use the full name diabetes mellitus, rather than diabetes alone, to distinguish this disorder from diabetes insipidus. Diabetes insipidus is a relatively rare disorder that does not affect blood glucose levels but, just like diabetes mellitus, also causes increased urination.
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.
After a diagnosis of diabetes mellitus has been made, and treatment with insulin therapy has begun, a so-called ‘honeymoon stage’ may develop. This stage is characterised by a reduction in insulin requirements which may last from weeks to months. Some patients may require no insulin at all. This stage is always transient (short-lasting) and is due to production of insulin by the remaining surviving pancreatic beta cells. Eventually, these cells will be destroyed by the on-going auto-immune process, and the patient will be dependent on exogenous (artificial) insulin.
The prognosis for a person with this health condition is estimated to be a life expectancy of 10 years less than a person without diabetes. However, good blood sugar control and taking steps to prevent complications is shortening this gap and people with the condition are living longer than ever before. It can be reversed with diligent attention to changing lifestyle behaviors.
They may need to take medications in order to keep glucose levels within a healthy range. Medications for type 2 diabetes are usually taken by mouth in the form of tablets and should always be taken around meal times and as prescribed by the doctor. However, if blood glucose is not controlled by oral medications, a doctor may recommend insulin injections.
But if you’re struggling with weight loss, eating fewer foods with added sugar and fat can be a step in the right direction for improving your health and potentially reducing your diabetes risk. In fact, if you have been diagnosed with prediabetes, losing just 5 to 7 percent of your body weight can reduce your risk for type 2 diabetes, according to the CDC.
John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.