What is Diabetes?

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.

Over time, having too much glucose in your blood can cause health problems. Although diabetes has no cure, you can take steps to manage your diabetes and stay healthy.

Sometimes people call diabetes “a touch of sugar” or “borderline diabetes.” These terms suggest that someone doesn’t really have diabetes or has a less serious case, but every case of diabetes is serious.

What are the different types of diabetes?

The most common types of diabetes are type 1, type 2, and gestational diabetes.

Type 1 diabetes

If you have type 1 diabetes, your body does not make insulin. Your immune system attacks and destroys the cells in your pancreas that make insulin. Type 1 diabetes is usually diagnosed in children and young adults, although it can appear at any age. People with type 1 diabetes need to take insulin every day to stay alive.

Type 2 diabetes

If you have type 2 diabetes, your body does not make or use insulin well. You can develop type 2 diabetes at any age, even during childhood. However, this type of diabetes occurs most often in middle-aged and older people. Type 2 is the most common type of diabetes.

Gestational diabetes

Gestational diabetes develops in some women when they are pregnant. Most of the time, this type of diabetes goes away after the baby is born. However, if you’ve had gestational diabetes, you have a greater chance of developing type 2 diabetes later in life. Sometimes diabetes diagnosed during pregnancy is actually type 2 diabetes.

Other types of diabetes

Less common types include monogenic diabetes, which is an inherited form of diabetes, and cystic fibrosis-related diabetes External link.

How common is diabetes?

As of 2015, 30.3 million people in the United States, or 9.4 percent of the population, had diabetes. More than 1 in 4 of them didn’t know they had the disease. Diabetes affects 1 in 4 people over the age of 65. About 90-95 percent of cases in adults are type 2 diabetes.

Who is more likely to develop type 2 diabetes?

You are more likely to develop type 2 diabetes if you are age 45 or older, have a family history of diabetes, or are overweight. Physical inactivity, race, and certain health problems such as high blood pressure also affect your chance of developing type 2 diabetes. You are also more likely to develop type 2 diabetes if you have prediabetes or had gestational diabetes when you were pregnant. Learn more about risk factors for type 2 diabetes.

What health problems can people with diabetes develop?

Over time, high blood glucose leads to problems such as

  • heart disease
  • stroke
  • kidney disease
  • eye problems
  • dental disease
  • nerve damage
  • foot problems

Symptoms & Causes of Diabetes

What are the symptoms of diabetes?

Symptoms of diabetes include

  • increased thirst and urination
  • increased hunger
  • fatigue
  • blurred vision
  • numbness or tingling in the feet or hands
  • sores that do not heal
  • unexplained weight loss

Symptoms of type 1 diabetes can start quickly, in a matter of weeks. Symptoms of type 2 diabetes often develop slowly—over the course of several years—and can be so mild that you might not even notice them. Many people with type 2 diabetes have no symptoms. Some people do not find out they have the disease until they have diabetes-related health problems, such as blurred vision or heart trouble.

What causes type 1 diabetes?

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 External link are working to pinpoint causes of type 1 diabetes and possible ways to prevent or slow the disease.

What causes type 2 diabetes?

Type 2 diabetes—the most common form of diabetes—is caused by several factors, including lifestyle factors and genes.

Overweight, obesity, and physical inactivity

You are more likely to develop type 2 diabetes if you are not physically active and are overweight or obese. Extra weight sometimes causes insulin resistance and is common in people with type 2 diabetes. The location of body fat also makes a difference. Extra belly fat is linked to insulin resistance, type 2 diabetes, and heart and blood vessel disease. To see if your weight puts you at risk for type 2 diabetes, check out these Body Mass Index (BMI) charts.

Insulin resistance

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.

Genes and family history

As in type 1 diabetes, certain genes may make you more likely to develop type 2 diabetes. The disease tends to run in families and occurs more often in these racial/ethnic groups:

  • African Americans
  • Alaska Natives
  • American Indians
  • Asian Americans
  • Hispanics/Latinos
  • Native Hawaiians
  • Pacific Islanders

Genes also can increase the risk of type 2 diabetes by increasing a person’s tendency to become overweight or obese.

What causes gestational diabetes?

Scientists believe gestational diabetes, a type of diabetes that develops during pregnancy, is caused by the hormonal changes of pregnancy along with genetic and lifestyle factors.

Insulin resistance

Hormones produced by the placenta NIH external link contribute to insulin resistance, which occurs in all women during late pregnancy. Most pregnant women can produce enough insulin to overcome insulin resistance, but some cannot. Gestational diabetes occurs when the pancreas can’t make enough insulin.

As with type 2 diabetes, extra weight is linked to gestational diabetes. Women who are overweight or obese may already have insulin resistance when they become pregnant. Gaining too much weight during pregnancy may also be a factor.

Genes and family history

Having a family history of diabetes makes it more likely that a woman will develop gestational diabetes, which suggests that genes play a role. Genes may also explain why the disorder occurs more often in African Americans, American Indians, Asians, and Hispanics/Latinas.

What else can cause diabetes?

Genetic mutations NIH external link, other diseases, damage to the pancreas, and certain medicines may also cause diabetes.

Genetic mutations

  • Monogenic diabetes is caused by mutations, or changes, in a single gene. These changes are usually passed through families, but sometimes the gene mutation happens on its own. Most of these gene mutations cause diabetes by making the pancreas less able to make insulin. The most common types of monogenic diabetes are neonatal diabetes and maturity-onset diabetes of the young (MODY). Neonatal diabetes occurs in the first 6 months of life. Doctors usually diagnose MODY during adolescence or early adulthood, but sometimes the disease is not diagnosed until later in life.
  • Cystic fibrosis NIH external link produces thick mucus that causes scarring in the pancreas. This scarring can prevent the pancreas from making enough insulin.
  • Hemochromatosis causes the body to store too much iron. If the disease is not treated, iron can build up in and damage the pancreas and other organs.

Hormonal diseases

Some hormonal diseases cause the body to produce too much of certain hormones, which sometimes cause insulin resistance and diabetes.

  • Cushing’s syndrome occurs when the body produces too much cortisol—often called the “stress hormone.”
  • Acromegaly occurs when the body produces too much growth hormone.
  • Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone.

Damage to or removal of the pancreas

Pancreatitis, pancreatic cancer, and trauma can all harm the beta cells or make them less able to produce insulin, resulting in diabetes. If the damaged pancreas is removed, diabetes will occur due to the loss of the beta cells.

Medicines

Sometimes certain medicines can harm beta cells or disrupt the way insulin works. These include

  • niacin, a type of vitamin B3
  • certain types of diuretics, also called water pills
  • anti-seizure drugs
  • psychiatric drugs
  • drugs to treat human immunodeficiency virus (HIV NIH external link)
  • pentamidine, a drug used to treat a type of pneumonia External link
  • glucocorticoids—medicines used to treat inflammatory illnesses such as rheumatoid arthritis NIH external link, asthma NIH external link, lupus NIH external link, and ulcerative colitis
  • anti-rejection medicines, used to help stop the body from rejecting a transplanted organ

Statins, which are medicines to reduce LDL (“bad”) cholesterol levels, can slightly increase the chance that you’ll develop diabetes. However, statins help protect you from heart disease and stroke. For this reason, the strong benefits of taking statins outweigh the small chance that you could develop diabetes.

If you take any of these medicines and are concerned about their side effects, talk with your doctor.

Risk Factors for Type 2 Diabetes

Your chances of developing type 2 diabetes depend on a combination of risk factors such as your genes and lifestyle. Although you can’t change risk factors such as family history, age, or ethnicity, you can change lifestyle risk factors around eating, physical activity, and weight. These lifestyle changes can affect your chances of developing type 2 diabetes.

Read about risk factors for type 2 diabetes below and see which ones apply to you. Taking action on the factors you can change can help you delay or prevent type 2 diabetes.

You are more likely to develop type 2 diabetes if you

  • are overweight or obese
  • are age 45 or older
  • have a family history of diabetes
  • are African American, Alaska Native, American Indian, Asian American, Hispanic/Latino, Native Hawaiian, or Pacific Islander
  • have high blood pressure
  • have a low level of HDL (“good”) cholesterol, or a high level of triglycerides
  • have a history of gestational diabetes or gave birth to a baby weighing 9 pounds or more
  • are not physically active
  • have a history of heart disease or stroke
  • have depression NIH external link
  • have polycystic ovary syndrome NIH external link, also called PCOS
  • have acanthosis nigricans—dark, thick, and velvety skin around your neck or armpits

What can I do to prevent type 2 diabetes?

You can take steps to help prevent or delay type 2 diabetes by losing weight if you are overweight, eating fewer calories, and being more physically active. Talk with your health care professional about any of the health conditions listed above that may require medical treatment. Managing these health problems may help reduce your chances of developing type 2 diabetes. Also, ask your health care professional about any medicines you take that might increase your risk.

Preventing Type 2 Diabetes

Perhaps you have learned that you have a high chance of developing type 2 diabetes, the most common type of diabetes. You might be overweight or have a parent, brother, or sister with type 2 diabetes. Maybe you had gestational diabetes, which is diabetes that develops during pregnancy. These are just a few examples of factors that can raise your chances of developing type 2 diabetes.

Diabetes can cause serious health problems, such as heart disease, stroke, and eye and foot problems. Prediabetes also can cause health problems. The good news is that type 2 diabetes can be delayed or even prevented. The longer you have diabetes, the more likely you are to develop health problems, so delaying diabetes by even a few years will benefit your health. You can help prevent or delay type 2 diabetes by losing a modest amount of weight by following a reduced-calorie eating plan and being physically active most days of the week. Ask your doctor if you should take the diabetes drug metformin NIH external link to help prevent or delay type 2 diabetes.

How can I lower my chances of developing type 2 diabetes?

Research such as the Diabetes Prevention Program External link shows that you can do a lot to reduce your chances of developing type 2 diabetes. Here are some things you can change to lower your risk:

  • Lose weight and keep it off. You may be able to prevent or delay diabetes by losing 5 to 7 percent of your starting weight.1 For instance, if you weigh 200 pounds, your goal would be to lose about 10 to 14 pounds.
  • Move more. Get at least 30 minutes of physical activity 5 days a week. If you have not been active, talk with your health care professional about which activities are best. Start slowly to build up to your goal.
  • Eat healthy foods most of the time. Eat smaller portions to reduce the amount of calories you eat each day and help you lose weight. Choosing foods with less fat is another way to reduce calories. Drink water instead of sweetened beverages.

Ask your health care professional about what other changes you can make to prevent or delay type 2 diabetes.

Most often, your best chance for preventing type 2 diabetes is to make lifestyle changes that work for you long term. Get started with Your Game Plan to Prevent Type 2 Diabetes.

What should I do if my health care professional told me I have prediabetes?

Prediabetes is when your blood glucose, also called blood sugar, levels are higher than normal, but not high enough to be called diabetes. Having prediabetes is serious because it raises your chance of developing type 2 diabetes. Many of the same factors that raise your chance of developing type 2 diabetes put you at risk for prediabetes.

Other names for prediabetes include impaired fasting glucose or impaired glucose tolerance. Some people call prediabetes “borderline diabetes.”

About 1 in 3 Americans has prediabetes, according to recent diabetes statistics from the Centers for Disease Control and Prevention. You won’t know if you have prediabetes unless you are tested.

If you have prediabetes, you can lower your chance of developing type 2 diabetes. Lose weight if you need to, become more physically active, and follow a reduced-calorie eating plan.

Get started with Your Game Plan to Prevent Type 2 Diabetes. For more support, you can find a lifestyle change program near you through the National Diabetes Prevention Program.

If I had gestational diabetes when I was pregnant, how can I lower my chances of developing type 2 diabetes?

Gestational diabetes is a type of diabetes that develops during pregnancy. Most of the time, gestational diabetes goes away after your baby is born. Even if your gestational diabetes goes away, you still have a greater chance of developing type 2 diabetes within 5 to 10 years. Your child may also be more likely to become obese and develop type 2 diabetes later in life. Making healthy choices helps the whole family and may protect your child from becoming obese or developing diabetes.
 

Here are steps you should take for yourself and your child if you had gestational diabetes:

  • Get tested for diabetes 6 to 12 weeks after your baby is born. If your blood glucose is still high, you may have type 2 diabetes. If your blood glucose is normal, you should get tested every 3 years to see if you have developed type 2 diabetes.
  • Be more active and make healthy food choices to get back to a healthy weight.
  • Breastfeed your baby. Breastfeeding gives your baby the right balance of nutrients and helps you burn calories.
  • Ask your doctor if you should take the diabetes drug metformin to help prevent type 2 diabetes.1

Diabetes Tests & Diagnosis

Your health care professional can diagnose diabetes, prediabetes, and gestational diabetes through blood tests. The blood tests show if your blood glucose, also called blood sugar, is too high.

Do not try to diagnose yourself if you think you might have diabetes. Testing equipment that you can buy over the counter, such as a blood glucose meter, cannot diagnose diabetes.

Who should be tested for diabetes?

Anyone who has symptoms of diabetes should be tested for the disease. Some people will not have any symptoms but may have risk factors for diabetes and need to be tested. Testing allows health care professionals to find diabetes sooner and work with their patients to manage diabetes and prevent complications.

Testing also allows health care professionals to find prediabetes. Making lifestyle changes to lose a modest amount of weight if you are overweight may help you delay or prevent type 2 diabetes.

Type 1 diabetes

Most often, testing for type 1 diabetes occurs in people with diabetes symptoms. Doctors usually diagnose type 1 diabetes in children and young adults. Because type 1 diabetes can run in families, a study called TrialNet offers free testing to family members External link of people with the disease, even if they don’t have symptoms.

Type 2 diabetes

Experts recommend routine testing for type 2 diabetes if you

  • are age 45 or older
  • are between the ages of 19 and 44, are overweight or obese, and have one or more other diabetes risk factors
  • are a woman who had gestational diabetes

Medicare covers the cost of diabetes tests for people with certain risk factors for diabetes. If you have Medicare, find out if you qualify for coverage. If you have different insurance, ask your insurance company if it covers diabetes tests.

Though type 2 diabetes most often develops in adults, children also can develop type 2 diabetes. Experts recommend testing children between the ages of 10 and 18 who are overweight or obese and have at least two other risk factors for developing diabetes.

  • low birthweight
  • a mother who had diabetes while pregnant with them
  • any risk factor mentioned in Risk Factors for Type 2 Diabetes

What test numbers tell me if I have diabetes or prediabetes?

Each test to detect diabetes and prediabetes uses a different measurement. Usually, the same test method needs to be repeated on a second day to diagnose diabetes. Your doctor may also use a second test method to confirm that you have diabetes.

The following table helps you understand what your test numbers mean if you are not pregnant.

Which tests help my health care professional know what kind of diabetes I have?

Even though the tests described here can confirm that you have diabetes, they can’t identify what type you have. Sometimes health care professionals are unsure if diabetes is type 1 or type 2. A rare type of diabetes that can occur in babies, called monogenic diabetes, can also be mistaken for type 1 diabetes. Treatment depends on the type of diabetes, so knowing which type you have is important.

To find out if your diabetes is type 1, your health care professional may look for certain autoantibodies. Autoantibodies are antibodies that mistakenly attack your healthy tissues and cells. The presence of one or more of several types of autoantibodies specific to diabetes is common in type 1 diabetes, but not in type 2 or monogenic diabetes. A health care professional will have to draw your blood for this test.

If you had diabetes while you were pregnant, you should get tested no later than 12 weeks after your baby is born to see if you have type 2 diabetes.

Managing Diabetes

You can manage your diabetes and live a long and healthy life by taking care of yourself each day.

Diabetes can affect almost every part of your body. Therefore, you will need to manage your blood glucose levels, also called blood sugar. Managing your blood glucose, as well as your blood pressure and cholesterol, can help prevent the health problems that can occur when you have diabetes.

How can I manage my diabetes?

With the help of your health care team, you can create a diabetes self-care plan to manage your diabetes. Your self-care plan may include these steps:

Ways to manage your diabetes

  • Manage your diabetes ABCs.
  • Follow your diabetes meal plan.
  • Make physical activity part of your routine.
  • Take your medicine.
  • Check your blood glucose levels.
  • Work with your health care team.
  • Cope with your diabetes in healthy ways.

Manage your diabetes ABCs

Knowing your diabetes ABCs will help you manage your blood glucose, blood pressure, and cholesterol. Stopping smoking if you smoke will also help you manage your diabetes. Working toward your ABC goals can help lower your chances of having a heart attack, stroke, or other diabetes problems.

A for the A1C test

The A1C test shows your average blood glucose level over the past 3 months. The A1C goal for many people with diabetes is below 7 percent. Ask your health care team what your goal should be.

B for Blood pressure

The blood pressure goal for most people with diabetes is below 140/90 mm Hg. Ask what your goal should be.

C for Cholesterol

You have two kinds of cholesterol in your blood: LDL and HDL. LDL or “bad” cholesterol can build up and clog your blood vessels. Too much bad cholesterol can cause a heart attack or stroke. HDL or “good” cholesterol helps remove the “bad” cholesterol from your blood vessels.

Ask your health care team what your cholesterol numbers should be. If you are over 40 years of age, you may need to take a statin drug for heart health.

S for Stop smoking

Not smoking is especially important for people with diabetes because both smoking and diabetes narrow blood vessels. Blood vessel narrowing makes your heart work harder. E-cigarettes aren’t a safe option either.

If you quit smoking

  • you will lower your risk for heart attack, stroke, nerve disease, kidney disease, diabetic eye disease, and amputation
  • your cholesterol and blood pressure levels may improve
  • your blood circulation will improve
  • you may have an easier time being physically active

If you smoke or use other tobacco products, stop. Ask for help so you don’t have to do it alone. You can start by calling the national quitline at 1-800-QUITNOW or 1-800-784-8669. For tips on quitting, go to SmokeFree.gov External link.

Keeping your A1C, blood pressure, and cholesterol levels close to your goals and stopping smoking may help prevent the long-term harmful effects of diabetes. These health problems include heart disease, stroke, kidney disease, nerve damage, and eye disease. You can keep track of your ABCs with a diabetes care record (PDF, 568 KB). Take it with you on your health care visits. Talk about your goals and how you are doing, and whether you need to make any changes in your diabetes care plan.

Follow your diabetes meal plan

Make a diabetes meal plan with help from your health care team. Following a meal plan will help you manage your blood glucose, blood pressure, and cholesterol.

Choose fruits and vegetables, beans, whole grains, chicken or turkey without the skin, fish, lean meats, and nonfat or low-fat milk and cheese. Drink water instead of sugar-sweetened beverages. Choose foods that are lower in calories, saturated fat, trans fat, sugar, and salt. Learn more about eating, diet, and nutrition with diabetes.

Make physical activity part of your daily routine

Set a goal to be more physically active. Try to work up to 30 minutes or more of physical activity on most days of the week.

Brisk walking and swimming are good ways to move more. If you are not active now, ask your health care team about the types and amounts of physical activity that are right for you. Learn more about being physically active with diabetes.

Following your meal plan and being more active can help you stay at or get to a healthy weight. If you are overweight or obese, work with your health care team to create a weight-loss plan that is right for you.

Take your medicine

Take your medicines for diabetes and any other health problems, even when you feel good or have reached your blood glucose, blood pressure, and cholesterol goals. These medicines help you manage your ABCs. Ask your doctor if you need to take aspirin to prevent a heart attack or stroke. Tell your health care professional if you cannot afford your medicines or if you have any side effects from your medicines. Learn more about insulin and other diabetes medicines.

Check your blood glucose levels

For many people with diabetes, checking their blood glucose level each day is an important way to manage their diabetes. Monitoring your blood glucose level is most important if you take insulin. The results of blood glucose monitoring can help you make decisions about food, physical activity, and medicines.

The most common way to check your blood glucose level at home is with a blood glucose meter. You get a drop of blood by pricking the side of your fingertip with a lancet. Then you apply the blood to a test strip. The meter will show you how much glucose is in your blood at the moment.

Ask your health care team how often you should check your blood glucose levels. Make sure to keep a record of your blood glucose self-checks. You can print copies of this glucose self-check chart (PDF, 2 MB). Take these records with you when you visit your health care team.

What is continuous glucose monitoring?

Continuous glucose monitoring (CGM) is another way to check your glucose levels. Most CGM systems use a tiny sensor that you insert under your skin. The sensor measures glucose levels in the fluids between your body’s cells every few minutes and can show changes in your glucose level throughout the day and night. If the CGM system shows that your glucose is too high or too low, you should check your glucose with a blood glucose meter before making any changes to your eating plan, physical activity, or medicines. A CGM system is especially useful for people who use insulin and have problems with low blood glucose.

What are the recommended targets for blood glucose levels?

Many people with diabetes aim to keep their blood glucose at these normal levels:

  • Before a meal: 80 to 130 mg/dL
  • About 2 hours after a meal starts: less than 180 mg/dL

Talk with your health care team about the best target range for you. Be sure to tell your health care professional if your glucose levels often go above or below your target range.

What happens if my blood glucose level becomes too low?

Sometimes blood glucose levels drop below where they should be, which is called hypoglycemia. For most people with diabetes, the blood glucose level is too low when it is below 70 mg/dL.

Hypoglycemia can be life threatening and needs to be treated right away. Learn more about how to recognize and treat hypoglycemia.

What happens if my blood glucose level becomes too high?

Doctors call high blood glucose hyperglycemia.

Symptoms that your blood glucose levels may be too high include

  • feeling thirsty
  • feeling tired or weak
  • headaches
  • urinating often
  • blurred vision

If you often have high blood glucose levels or symptoms of high blood glucose, talk with your health care team. You may need a change in your diabetes meal plan, physical activity plan, or medicines.

Know when to check for ketones

Your doctor may want you to check your urine NIH external link for ketones if you have symptoms of diabetic ketoacidosis NIH external link. When ketone levels get too high, you can develop this life-threatening condition. Symptoms include

  • trouble breathing
  • nausea or vomiting
  • pain in your abdomen
  • confusion
  • feeling very tired or sleepy

Ketoacidosis most often is a problem for people with type 1 diabetes.


Reference: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Last Updated: March 2020

Diabetes

This information is for general educational uses only. It may not apply to you and your personal medical needs. This information should not be used in place of a visit, call, consultation with or the advice of your physician or health care professional.

Communicate promptly with your physician or other health care professional with any health-related questions or concerns.

Be sure to follow specific instructions given to you by your physician or health care professional.

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