Skip to Accessibility Tools Skip to Content Skip to Footer

What is type 2 diabetes?

Type 2 diabetes… the basics

Diabetes includes a group of diseases of which there are three main types: type 1 diabetes mellitus, type 2 diabetes mellitus, and gestational diabetes. Diabetes is a disorder of metabolism, a word that means how our body uses the food we digest for growth and energy. In other words, with diabetes something goes wrong with the way our body processes the food we take in, interfering with our ability to use that food for energy and to maintain our health.

Of the three main forms of diabetes, type 2 diabetes mellitus is by far the most common. It accounts for over 90% of cases of diabetes. All forms of diabetes are characterized by high levels of sugar in the blood (this is described as “high blood sugar” or “high blood glucose”).1

Type 2 diabetes and high blood glucose

We need some basic information about food and nutrition to understand why the high blood sugar that occurs with diabetes is a problem. Our bodies require energy to function properly and we get that energy from the foods we eat. Our diet (everything we eat and drink) includes three main sources of energy (also known as calories): protein, fat, and carbohydrates (sugars, starches, and fibers).When the body digests most sources of carbohydrates, they are transformed through digestion into a very important source of instant energy, a form of sugar called glucose.1-3

Our bodies depend on the action of a number of different natural body chemicals called hormones, working together in conjunction, to control how we use glucose. These include insulin, a hormone produced in the beta cells of the pancreas (an organ located behind the stomach) that serves as sort of a “gate keeper,” allowing glucose to enter cells where it can be transformed into energy and used to support vital cell functions. In addition to insulin, the other hormones involved in glucose control include amylin, a group of hormones called incretins, which are produced in the intestine, and glucagon, which is produced in the pancreas.3,4

What happens in type 2 diabetes is that the body loses the ability to use the insulin it produces effectively (this is called “insulin resistance”). We know that being overweight starts the process of events inside the body that leads to the development of insulin resistance.3,4

In addition to insulin resistance, loss of the ability to produce insulin also plays a role in elevated blood glucose. In fact, by the time that most people are diagnosed with type 2 diabetes, they have already lost over 50% of their ability to make the insulin they need. In addition to a deficiency in insulin, abnormalities with the other hormones involved in glucose control can also contribute to type 2 diabetes. The process that leads to the development of type 2 diabetes, involving insulin resistance and loss of the ability to produce insulin, can begin well before a person is diagnosed with type 2 diabetes. In many people, insulin resistance and decreased insulin production develops over a period of 5 to 10 years before high blood sugar is detected.5

Learn more about how insulin and other hormones are involved in glucose control.

Type 2 diabetes: a disease of multiple organs and tissues

Just as there are multiple hormones in the body that are involved in the disease process of type 2 diabetes, the latest research also shows that high blood glucose in type 2 diabetes is driven not by a single organ, such as the pancreas, but by multiple organs and tissues, including the muscle cells, fat cells, the liver, the pancreas, the intestine, the kidney, and the brain, that all contribute to promote high blood glucose.

What’s in a name?

Many diseases, including diabetes (the full name is diabetes mellitus), get their names from ancient languages—often from Latin and Greek, because ancient Greek and Roman physicians were among the first to carefully describe those diseases. Because of their ancient origins, many disease names can seem distant and mysterious (as well as difficult to pronounce!).2

However, if we can get beyond the strangeness of the word, we often find that the name describes something essential about the disease. Diabetes mellitus is a perfect example. We already know that diabetes involves high blood sugar resulting from an inability of the body to use insulin normally or decreased insulin production by the pancreas or a combination of these.

High blood sugar that persists over time puts a great deal of stress on our kidneys, which are responsible for maintaining a balance between the mix of chemicals in the water contained within the body. The kidneys produce urine as a means of ridding the body of waste products and maintaining this critical balance, so when high levels of sugar build up in the blood, the kidney responds by producing excess urine to get rid of this sugar. This explains several of the key symptoms of diabetes, including excess urine production, dehydration, and thirst.

It also explains why the ancient Greeks used the word diabetes to describe the disease. In Greek, the word diabetes literally means passing through and was used to describe the fact that people with the disease produced excess urine. Liquids seemed to pass straight through the body. What’s more, the urine of people with diabetes had so much excess sugar that it tasted sweet. (Ancient doctors didn’t have our sophisticated testing instruments, so they relied more on their senses.) This is where the word mellitus in diabetes mellitus comes from. The word mellitus is from the Greek and Latin words for sweetness or honey. The Greeks appeared to have imported honey from the island nation of Malta, which served as both the source of honey, as well as the source of the Greek and Latin words used to describe it.2

How is type 2 diabetes different from the other common forms of diabetes?

Type 1 diabetes differs from type 2 diabetes. It is an autoimmune disease, in which the body’s immune system malfunctions and turns against healthy tissue. In the case of type 1 diabetes, the body’s immune system attacks the beta cells in the pancreas that produce insulin, with the result that little or no insulin is produced. Gestational diabetes develops in some women during pregnancy. Typically, although not always, gestational diabetes resolves after birth. Among women with gestational diabetes, 5% to 10% are found to have diabetes (usually type 2) after pregnancy.1,6

Symptoms and signs of type 2 diabetes

Type 2 diabetes can be associated with symptoms, including fatigue, frequent urination, increased thirst and hunger, and blurred vision. However, most people don’t experience any symptoms and are surprised by the diagnosis.1

Learn more about symptoms that can occur with type 2 diabetes

Diagnosis of type 2 diabetes

Since most people who develop type 2 diabetes do not experience symptoms, measuring excess blood sugar or blood glucose levels is the main way to diagnose diabetes. In most cases, diabetes will be detected during routine laboratory testing as part of a check-up.

Four different tests are used to measure blood glucose and can be used to diagnose diabetes. These include7:

    • Random blood sugar test: blood test taken at any time during the day, regardless of when you last ate
    • Fasting blood sugar test: blood test taken after fasting (not eating or drinking) for 8 to 12 hours (typically you fast overnight and have blood drawn in the morning)
    • Oral glucose tolerance test: blood test taken before and 2 hours after drinking a special glucose solution (this test is typically used only with gestational diabetes)
    • Hemoglobin A1C test (known as “A1C”): blood test taken at any time of day (before or after a meal) that measures average blood sugar level over a 2 to 3 month period.

Learn more about diagnosis of type 2 diabetes…

Important things to keep in mind…

If you have been diagnosed with type 2 diabetes or if you have been told that you are at risk for the disease, you may be feeling overwhelmed. You probably have many questions about why the disease has affected you and what it will mean for your life (both your long-term health and daily living). You may have many practical questions, concerning blood sugar testing, treatment options, what you can and can’t eat.

Although getting the diagnosis of type 2 diabetes or being told you have prediabetes can be emotionally challenging, keep in mind some important facts. Most people with type 2 diabetes can:

  • Continue to lead full and active lives
  • Enjoy the foods and activities they have always enjoyed
  • Take part in almost any form of physical activity

Also, don’t lose sight that you have some pretty powerful resources that you can use to live a healthy and active life. These include your medical care team (your doctor and nurses), specialists including psychologist and social workers. Additionally, ask your doctor and nurse about the many group classes that are available to you locally. Group classes will connect you to other people just like you who are tackling the challenges of living with diabetes.

Getting the support and information you need to live a healthy life with type 2 diabetes

Be aware that you have some pretty powerful resources that you can use to live a healthy and active life if you have type 2 diabetes. These include your medical care team (your primary healthcare provider (doctor, physician assistant [PA], or nurse practitioner [NP]), diabetes educators, various healthcare specialists (eg, optometrists, podiatrists, psychologists). You can learn more about these and other key members of your diabetes care team at the ADA website (

Take advantage of Diabetes Self-Management Education and Support (DSMES)!

Medicare and by most private health insurance plans will cover DSMES services if you have type 2 diabetes. These service cover diabetes education and support provided by a American Association of Diabetes Educators (AADE)-certified diabetes educator. A diabetes educator is a healthcare professional who specializes in helping people with and at risk for diabetes and related complications to make behavioral changes designed to help them better manage their condition and lead a healthier life. DSMES services focus on seven important self-care behaviors that are keys to living a healthy life with type 2 diabetes:

  • Healthy eating
  • Being active
  • Monitoring blood glucose
  • Taking medication
  • Problem solving
  • Healthy coping
  • Reducing risks for health complications

Ask your doctor, PA, or NP to refer you to a local DSMES provider. If your provider is not familiar with DSMES services or the referral process, you can direct them to the AADE website or download and print DSMES information and a referral form and give it to your provider yourself.

Written by: Jonathan Simmons | Last reviewed: May 2014.
1. Diabetes Overview. National Diabetes Information Clearinghouse (NDIC). Available at: Accessed 12/04/13. -- 2. Franz MJ, Evert AB. American Diabetes Association Guide to Nutrition Therapy for Diabetes. 2nd ed. Alexandria, VA: American Diabetes Association; 2012. -- 3. Mantzoros C, Serdy S. Insulin action. Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: 2013. - 4. Inzucchi SE, Bergenstal RM, Buse JB, et al. Management of hyperglycemia in type 2 diabetes: a patient-centered approach: position statement of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD). Diabetes Care 2012;35:1364-79. 5. Warshaw HS. Nutrition therapy for adults with type 2 diabetes. In: Franz MJ, Evert AB, eds. American Diabetes Association Guide to Nutrition Therapy for Diabetes. 2nd ed. Alexandria, VA: American Diabetes Association; 2012. 6. National diabetes fact sheet: national estimates and general information on diabetes and prediabetes in the United States, 2011. Atlanta, GA: US DHHS, CDC; 2011. 7. McCulloch DK. Clinical presentation and diagnosis of diabetes mellitus in adults. Nathan DM, Wolfsdorf JI, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: 2013.