PREDIABETES AND TYPE 2 DIABETES | Added: 12, August 2017


What is prediabetes?

Prediabetes is a condition that often (but not always) occurs before a person develops type 2 diabetes. It is characterized by somewhat high blood glucose levels, which are caused by either a lack of insulin in the body or the body’s inability to efficiently use insulin produced by the pancreas. In terms of measurement, prediabetes is considered to be present if blood glucose levels are higher than normal but not enough to be a diagnosis of diabetes.

How does a person know if he or she has prediabetes?

For most people, there are no clear symptoms of prediabetes. In most cases, a person discovers he or she has prediabetes after a routine blood test or diabetes test. Because blood glucose levels rise slowly over time, a person may develop indicators of diabetes gradually or not at all, and thus, the symptoms may be overlooked. In addition, many of the symptoms experienced by a person who is prediabetic may be discounted, as they often represent several other conditions. This is also why prediabetes may go undiagnosed for years (and an often subsequent diagnosis of diabetes for many years, too).

What are the major tests health care professionals use to diagnose prediabetes?

When a person has blood glucose levels-usually determined through a fasting plasma-glucose test-slightly above the normal range but not high enough to be diagnosable as diabetes, he or she is considered prediabetic. The following list, from Harvard Medical School and the American Diabetes Association, shows ranges of various tests that indicate whether a person is at high risk for developing diabetes (the random plasma-glucose test is not usually used to determine prediabetes; for more about the following tests, and the random plasma-glucose test, see the chapter “Taking Charge of Diabetes”). The symbols “mg/dl” represent milligrams per deciliter:

Glycated hemoglobin (or HbA1c or simply A1c) can be measured to determine plasma glucose levels.

Fasting plasma glucose (or fasting blood glucose): 100 mg/dl to 125 mg/dl (if a person’s number is in this range, it is often called impaired fasting glucose)

Oral glucose tolerance (or OGTT 2-hour blood glucose): 140 mg/dl to 199 mg/dl (if a person’s number is in this range, it is often called impaired glucose tolerance)

HbA1c (also called A1C or A1c): 5.7 to 6.4 percent

Are the terms impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) both synonymous with prediabetes?

Many people have impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), two ways of expressing what is commonly referred to as prediabetes. As the name “prediabetes” suggests, the condition occurs when a person has a higher blood glucose level than what is considered normal but one that is still below what is considered diabetes. These levels are usually measured by a blood glucose test. Doctors often refer to a person with prediabetes as having impaired glucose intolerance or impaired fasting glucose depending on the test that was used when the prediabetes was detected.

Who is at most risk for prediabetes?

The people who seem to be most at risk for developing prediabetes are most often overweight or obese because the majority of people who develop type 2 diabetes carry extra weight. In addition, some people with prediabetes may already have some of the symptoms of type 2 diabetes or even the problems associated with the disease.

Are there any symptoms if a person is prediabetic?

There are several signs that a person may be on the road toward developing diabetes. There are usually seven warning signs, and many of them mimic or seem to be symptoms of other ailments. For this reason, it is estimated that of the one in four people who has prediabetes, only about 4 percent know it. This means 96 percent of the population with prediabetes does not know it is at risk of developing type 2 diabetes. The “hidden” signs, as they are often called, are ones that increase a person’s risk of developing diabetes and include the following:

Red, swollen, and/or tender gums-It is estimated that nine out of ten people with gum disease are at high risk for diabetes. This is compared to six out of ten without gum disease. Although some people have a predisposition to gum disease or have certain diseases that can affect their gums, it is often thought that people with gum disease who do not have diabetes check their blood glucose levels at least once a year.

High blood pressure-There are several statistics when it comes to high blood pressure, and especially involving women developing type 2 diabetes. It is estimated that women with high blood pressure are more than twice as likely to develop type 2 diabetes over a ten-year period as women with normal blood pressure. There is thought to be an elevated risk to women even if their blood pressure is a bit higher or when their blood pressure slowly rises over time.

Gastrointestinal problems-People who are prediabetic also have more upper-gastrointestinal problems. These include heartburn, acid reflux, some indigestion, and chest pain (not associated with heart disease). Also included are people who have ulcer-like pains that cause them to wake up at night but find that the pain goes away when they eat.

Thirst-Being thirsty much of the time is one of the classic symptoms not only of full-blown diabetes but also of prediabetes. This is because sugar tends to build up in the bloodstream when a person has the beginnings of diabetes (and with diabetes). This buildup causes the sugar to spill into the urine, and the kidneys begin to excrete more water in order to dilute the sugar. This process causes people to generate a great deal of urine, making them go to the bathroom more often-and making them thirstier as they lose fluids.

Why do some people seem to lose weight at the onset of diabetes-and sometimes after the diagnosis?

Many people with prediabetes-and even those with uncontrolled diabetes-seem to eat more during the day. This is because of insulin resistance (meaning their cells ignore insulin), which means it is difficult for glucose to get into the body’s cells. This problem makes the muscles and organs want more energy, which means the person will burn fat and muscle to obtain that energy. Thus, they will lose weight, but in reality they are losing healthy muscle mass and not as much fat. This is because without a constant source of glucose in the body, the muscle tissues shrink over time. Such weight loss (or sometimes the inability to gain weight) is most notable in people with type 1 diabetes. It also occurs in people with type 2 diabetes, but because they are often overweight or obese to begin with, such weight loss goes virtually unnoticed.

Numbness, burning pain, or tingling sensations-This is especially true in the extremities, namely the hands and feet.

Wounds that heal slowly-This is also a sign of prediabetes, especially as the person’s blood glucose levels begin to rise.

Confusion and fatigue-This is a more difficult symptom to connect to prediabetes. But for people who are developing diabetes, there are often signs of confusion and general fatigue.

At what age should a person who may be at risk for diabetes be tested for prediabetes?

There are some indications that a person may be prediabetic, but the most common way it is detected is through a fasting blood glucose test. Many health care professionals suggest a person undergo a fasting blood glucose test after age 45, with some even suggesting their younger patients be tested after age 20, especially if there is a history of type 2 diabetes in the patient’s family.

What are some of the risks of being prediabetic?

Most people with prediabetes have a higher risk of becoming a type 2 diabetic, which is why health care professionals suggest that people who are diagnosed as prediabetic should have their glucose levels checked once a year (or more, if the doctor prescribes such tests). In fact, some statistics estimate that about half of people with prediabetes will go on to develop type 2 diabetes. In addition, this condition puts a person at a higher risk for developing cardiovascular and other related diseases. (For more information about cardiovascular disease, see the chapter “How Diabetes Affects the Circulatory System.”)

But many people who are diagnosed with prediabetes never develop type 2 diabetes. In the majority of cases, this is because they change their lifestyle habits, including eating more healthfully, exercising more, and lowering their stress.


How can most people lower their risk of developing prediabetes and eventually type 2 diabetes?

For many people, there are ways to lower the risk of developing type 2 diabetes. In fact, according to the American Diabetes Association, a person can often lower his or her risk by about 58 percent by losing 7 percent of their body weight (for example, if a person weighs 200 pounds [90.7 kilograms], losing about 15 pounds [6.8 kilograms]) and by exercising moderately (for example, brisk walking) for 30 minutes a day, five days a week. In the same example as above, if a person weighs 200 pounds, even losing 10 pounds (4.5 kilograms) will make a big difference and lower the risk of developing type 2 diabetes. (It should be noted that for some people such measures may only slow the disease down. For example, those who have a genetic predisposition to diabetes or have other medical problems may still have an increased risk for developing type 2 diabetes.)

For many people who are prediabetic, losing a few pounds and getting regular exercise can stave off full-blown diabetes.

What are some foods to avoid in order to lower the risk of developing type 2 diabetes?

Not all foods lead to diabetes, but some are more likely than others to increase the risk of diabetes. For example, foods high in saturated fats, trans-fatty acids, and fructose, along with highly processed foods, can contribute to a person’s chances of getting type 2 diabetes. This is because many of those foods cause excess weight gain-especially if the person does not get much exercise-and additional weight sometimes increases a person’s risk of developing type 2 diabetes. (For more about foods and type 2 diabetes, see the chapters “Diabetes and Nutrition” and “Diabetes and Eating.”)

If a person is prediabetic, will he or she always become diabetic?

According to Harvard Medical School, having prediabetes is no guarantee that a person will develop full-blown diabetes. What a prediabetes diagnosis means is that the person has a risk of developing type 2 diabetes. There are some often-debated averages concerning whether a person with prediabetes will develop full-blown type 2 diabetes. Some research indicates that half of the people with prediabetes will develop type 2. Other research suggests that about a quarter of people with prediabetes will develop type 2 and around half will stay in the prediabetic stage. The rest (the last quarter) will not develop type 2 diabetes and will revert to having normal blood glucose levels, mostly through lifestyle changes. Either way, most experts agree that being diagnosed with prediabetes should be a wake-up call for people to pay attention to their lifestyle in order to avoid developing type 2 diabetes.


What percentage of people with type 2 diabetes are said to be obese?

In general, it is thought that about 90 to 95 percent of people with diabetes have type 2 diabetes, with almost 80 percent of those people said to be obese. Some research also indicates that the number of people who are obese and have type 2 diabetes are on the rise, not only in the United States but all over the world.

How fast does type 2 diabetes develop?

There is truly no set “timetable” for when a person develops type 2 diabetes. Some studies indicate that if a person does not make changes to diet or exercise-or lifestyle changes-after being diagnosed with prediabetes, they have about a 50 percent chance of developing type 2 diabetes within ten years. This is not true for everyone who develops type 2 diabetes, as genetics or other conditions can lead to the disease, but on the average most people can stop or slow down the progression with lifestyle changes.

What is thought to be a major risk factor in developing type 2 diabetes?

Although there can be several reasons for developing type 2 diabetes, research has shown that excess body fat is a major risk factor. In fact, people who are obese-those with a body mass index (BMI) of over 30-apparently have 100 times more risk of developing type 2 diabetes than people who have a lower BMI. (For more about body mass index, see the chapter “Diabetes and Obesity.”)

Is there a “standard” type of person who has type 2 diabetes?

In treating type 2 diabetes one must remember that people differ in size, shape, health risks, and medical problems. Thus, there is not a “standard” person with type 2 diabetes. But doctors do mention common characteristics of a person with type 2 diabetes, including a lack of exercise, obesity, high blood pressure, and even a group of conditions called the metabolic syndrome. (For more about metabolic syndrome, see this chapter.)

Type 2 diabetes results when the pancreas does not make enough insulin to carry sufficient amounts of glucose to the blood.

What are the warning signs of type 2 diabetes?

There are several warning signs of type 2 diabetes, although some people don’t have such obvious signs. The following lists some of the general, traditional type 2 diabetes symptoms, which are similar to the type 1 warning signs:

The onset is apparently sudden, although for many people (especially children) it may seem to occur slowly as some of the symptoms mimic other conditions.

The person urinates frequently, as the body tries to rid itself of the excessive amounts of blood glucose.

The person has excessive thirst as he or she urinates more frequently.

The person may also find that cuts and bruises are slow to heal; the person may also have frequent infections.

As the disease develops, the person may become progressively hungry, as the body burns its own fat for energy.

Even though the person may be hungry and eat more, there may also be some sudden weight loss as the body continues to burn its own fat.

Because the cells are not able to receive the sugar they need (due to poor insulin function), the person can become ill-tempered because of fatigue.

The person may have tingling or numbness in the hands and/or feet.

The person may also have vision problems; this is caused because as the blood glucose increases, fluid may be pulled from the lenses of the person’s eyes, causing blurred vision.

Some people with type 2 diabetes may have areas of dark skin in the folds or creases of their body (the neck and armpits are the most common sites), which is often considered a sign of being resistant to insulin.

Although not as much of a sign as the others mentioned above, nausea and vomiting can accompany the disease in some people.

Why are health care professionals so concerned that people are having type 2 diabetes at younger ages?

Health care professionals have several concerns about young people developing type 2 diabetes. One reason is the management of the disease, especially for those who are trying to maintain a balanced blood sugar throughout the day while in school (for more about diabetes and school, see the chapter “Who Gets Diabetes”). But one of the major reasons for concern is the risk of complications: the risk of heart attack, stroke, blindness, kidney failure, and amputations becomes greater the longer a person has diabetes.

What gene was recently studied in connection with type 2 diabetes?

In 2016, it was announced that an international team of researchers had identified a gene that may be responsible for the development of type 2 diabetes. The scientists, led by a team from Flinders University in Australia, found a single gene called RCAN1 that may hold a key to the future of type 2 diabetes prevention. The researchers cross-referenced genes from people with Down syndrome, a genetic condition in which a person has an extra copy of chromosome 21 (the extra genetic material is called overexpression of particular genes). People with Down are also more likely to develop type 2 diabetes, as many have lower insulin secretion. The researchers looked at over 5,000 genes in four mouse models of Down syndrome (two exhibited high blood sugar, two did not). They then found 38 possible genes that were crossovers of Down and type 2 diabetes. Researchers noticed that when one gene called RCAN1 was overexpressed in mice, the mice secreted less insulin in the presence of high glucose. Thus, they extrapolated that RCAN1 may be responsible for type 2 diabetes in humans. Although it is unknown what types of changes occur in the pancreas to make the transition to type 2 diabetes, this discovery may lead to uncovering a primary cause of the disease. More research needs to be done, of course, with the next steps including using drugs to target RCAN1 and to see whether any of those drugs improves insulin secretion. Diabetes researchers hope that targeting this gene will eventually lead to possible prevention or reversal of type 2 diabetes. (For more about the future of genetics and diabetes, see the chapter “The Future and Diabetes.”)

At what age can a person develop type 2 diabetes?

A person can develop type 2 diabetes at almost any age. Even young children can develop type 2 diabetes, and in the past decade, the number of youngsters with the disease has grown. In fact, the youngest person on record to be diagnosed with type 2 diabetes was around three years old. (For more about young people and type 2 diabetes, see the chapter “Who Gets Diabetes?”)

What other diseases (besides diabetes) are associated with insulin resistance?

Insulin resistance is a condition in which the body’s natural hormone insulin is less effective in reducing a person’s blood glucose (sugar) levels. This causes blood glucose levels to rise, and if the increase becomes more severe, it can lead to type 2 diabetes and potential adverse health effects. But other diseases are also associated with insulin resistance, including metabolic syndrome, hypertension, and nonalcoholic fatty liver disease.

Why do people often develop insulin resistance with type 2 diabetes?

The body’s fat and muscle cells (and all other cells in the body) require insulin in order to absorb the glucose from certain foods. That glucose, in turn, gives the cells energy. For a person with type 2 diabetes, there are three causes of insulin resistance: the person’s muscles are not taking up glucose as they should, so there is an excess amount of glucose in the blood; the liver is taking up too little glucose and is even over-secreting glucose into the bloodstream; and the insulin production in the pancreas is not keeping up with the high levels of glucose in the bloodstream. As this system breaks down, the primary problem seems to be insulin resistance in the liver and the muscles. The person’s blood glucose levels rise, but the body’s cells cannot take in the glucose because of the lack of insulin.

Beta cells in the pancreas are in charge of storing and releasing insulin. If they malfunction, diabetes can result.

Why do beta cells in the pancreas play a role in insulin resistance?

In most cases, people with type 2 diabetes have insulin resistance caused by a problem with the beta cells in the pancreas, specifically if the cells do not make enough insulin to keep up with resistance and/or if the beta cells become depleted. (For more about the pancreas and insulin, see the chapter “How Diabetes Affects the Endocrine System.”)

How is insulin resistance measured?

Insulin resistance is measured by taking a person’s fasting insulin level or giving a glucose-tolerance test. There is also a test called the hyperinsulinemic euglycemic clamp to measure insulin resistance, which many consider one of the best indicators of insulin resistance. In addition, there are several other tests, such as the homeostatic model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI), and the modified insulin-suppression test.

What are some risk factors linked to insulin resistance in a person with type 2 diabetes?

Several factors may contribute to a person’s developing insulin resistance. These include a genetic risk (especially if a family member has type 2 diabetes); having insulin receptor mutations (called Donohue syndrome); and being African American, Hispanic, American Indian, or Asian. Other risk factors include being between the ages of 40 and 45, being obese, having a sedentary lifestyle, high triglyceride levels, hypertension, pre-diabetes, having had gestational diabetes (and having a baby who was more than nine pounds [four kilograms] at birth), and where a person stores fat (especially if the fat is mostly in the abdomen rather than in the hips and thighs).

What is one way that may help lower the risk of developing insulin resistance that could lead to type 2 diabetes?

Similar to what most doctors recommend for any type of diabetes, two of the best ways to lower the risk of developing insulin resistance are exercise and weight loss.


What is metabolic syndrome and its connection to diabetes?

Metabolic syndrome (once called Syndrome X) is a cluster of metabolic risk factors that a person has, all putting the person at risk for various diseases. One of the major traits of metabolic syndrome is obesity, or being overweight, either through poor eating habits, not enough exercise, or other factors. Found mostly in adults (many with prediabetes), obesity includes too much fat around the waist (in other words, a large waist measurement), high blood pressure, high triglycerides, and abnormal blood fats (especially certain cholesterol levels).

In terms of diabetes, metabolic syndrome also includes high blood glucose levels, which go hand-in-hand with glucose intolerance. Not only does metabolic syndrome predict an increased risk of diabetes, it also predicts cardiovascular disease. (For more about cardiovascular disease, see the chapter “How Diabetes Affects the Circulatory System.”)

How many people are estimated to have metabolic syndrome in the United States?

It is estimated that about 34 percent of adults in the United States have metabolic syndrome. It is found to be higher in non-Hispanic white males than Mexican American and non-Hispanic black men. But in contrast, it is more common in Mexican American women than in non-Hispanic black or non-Hispanic white women.

What are the numbers behind metabolic-syndrome traits?

According to many organizations, such as the National Heart, Lung, and Blood Institute (NHLBI), the American Diabetes Association, the American Heart Association (AHA), and the Diabetes Prevention Support Center, any three of the following five traits in the same person meet the criteria for metabolic syndrome. Many of these traits are related to the foods we eat (note: the term “mg/dl,” also seen as “mg/dL,” means milligrams per deciliter, a unit of measure):

Abdominal obesity-One metabolic syndrome trait is a high waist circumference, often called an “apple-shaped” body (as opposed to what is called a “pear-shaped” body). This means a waist circumference of 40 inches (102 centimeters) or more in men and 35 inches (88 centimeters) or more in women (there are also different criteria for various ethnic groups, too; for example, for Asian Americans, the values are greater than or equal to 35 inches [90 centimeters] in men and greater than or equal to 32 inches [80 centimeters] in women). (For more about abdominal obesity, see this chapter.)

Serum triglycerides (or triglycerides)-This reading is included in the test for metabolic syndrome if a person has a triglyceride reading of 150 mg/dl or above and is taking medicine for high triglycerides. (For more about triglycerides, see the chapter “How Diabetes Affects the Circulatory System.”)

Cholesterol-The cholesterol in the body has “good” and “bad” types. The “bad” cholesterol is LDL (low-density lipoprotein), but that reading is not used in determining metabolic syndrome. The “good” cholesterol, HDL (high-density lipoprotein), is used: If the HDL cholesterol reads 40 mg/dl or lower in men and 50 mg/dl or lower in women, then it is part of the list for metabolic syndrome. In addition, taking medicine for low HDL cholesterol is included in the metabolic-syndrome list. (For more about cholesterol-good and bad-see the chapter “How Diabetes Affects the Circulatory System.”)

Blood pressure-For blood pressure to be added to the list of metabolic-syndrome traits, there must be a reading of 130/85 or more (systolic over diastolic numbers), although this reading is often debated, usually in favor of a bit higher reading. Another trait of metabolic syndrome is taking medicine for high blood pressure. (For more about blood pressure, see the chapter “How Diabetes Affects the Circulatory System.”)

Blood glucose-Another metabolic-syndrome trait is high blood glucose levels. Levels of fasting blood glucose would measure 100 mg/dl or above (although this number is also debated, with several researchers suggesting it should be even lower). Taking medicine for high blood glucose is also included in metabolic syndrome.

A common sense treatment for obesity and related diseases such as metabolic syndrome is weight loss through exercise.

How is metabolic syndrome treated?

According to almost every health-related organization, such as the American Heart Association and the American Diabetes Association, there are several things a person with metabolic syndrome can do to help lower the risk of developing cardiovascular disease and/or diabetes. The major ways are for a person to lose weight, eat a healthy diet, and increase physical activity.


For adults between 18 and 45, what are some risk factors for developing type 2 diabetes?

People between the ages 18 and 45, and with a body mass index of 25 or higher (for more about body mass index, or BMI, see the chapter “Diabetes and Obesity”) should be tested if they have one of the following risk factors for developing type 2 diabetes:

The person has a mother, father, brother, or sister with diabetes.

The person is physically inactive.

The person is of African American, Asian American, Hispanic American, Native American, or Pacific Islander decent.

The person has given birth to a baby weighing more than 9 pounds (4 kilograms) or has had gestational diabetes during pregnancy (for more about gestational diabetes, see the chapter, “Other Types of Diabetes”).

The person has a blood pressure of around 140/90 mm Hg or higher or is being treated with blood pressure-lowering medications (for more about high blood pressure, see the chapter “How Diabetes Affects the Circulatory System”).

The person has abnormal blood lipid (fat) levels, such as HDL cholesterol levels below 35 mg/dl or triglyceride levels over 250 mg/dl. (For more about cholesterol and triglycerides, see the chapter “How Diabetes Affects the Circulatory System.”)

The person has measured levels that indicate impaired glucose tolerance or impaired fasting glucose after being tested for diabetes.

A female has polycystic ovary syndrome or (males and females) a history of vascular problems.

The person has an HbA1c level that is greater than 5.7 percent. (A reading of 5.7 percent means a person is not yet considered to have diabetes but has a higher chance of developing diabetes; health care professionals consider a person to be diabetic if the HbA1c number is greater than 6.5 percent.)

If one or more of these items fits a person, and he or she is found not to have diabetes, then the test should be repeated in three years or as the health care professional suggests-or repeated, of course, if the person starts to develop symptoms.

For a person older than 45, what are risk factors for developing type 2 diabetes?

There are several risk factors for type 2 diabetes for adults age 45 years or older. They include:

A family history of diabetes, especially in the immediate family.

Being overweight, and especially if a person is obese (generally a body mass index, or BMI, over 30; for more about BMI, see the chapter “Diabetes and Obesity”).

A lack of regular exercise (often connected with a sedentary lifestyle in older people).

Being from an ethnic or racial group that is more inclined to type 2 diabetes, including African Americans, American Indians, Hispanic Americans, Asian Americans, and Pacific Islanders.

Do people with type 2 diabetes ever need insulin injections instead of oral medication?

When people with type 2 diabetes have the disease for a long time, their use of oral medications may not work as well. Thus, one of the only ways to keep the blood glucose levels in balance is to begin using insulin. In combination with eating well, physical activity, and often other medications (including oral diabetes medicines), insulin becomes an additional help in controlling blood glucose levels. (For more about diabetes medications, see the chapter “Taking Charge of Diabetes.”)

What are some long-term complications of diabetes, especially type 2?

There are possible complications if a person has diabetes in the long term-in other words, the longer a person has diabetes, the more the possible risk of complications increases. These complications include heart attack, stroke, blindness, kidney failure, and amputations. But many of these risks can be mitigated or at least lessened by rigorous blood-sugar control and also by treating a diabetic for high blood pressure and/or high cholesterol if necessary.