Type 2 Diabetes Mellitus

Type 2 diabetes is a chronic condition where your body struggles to use insulin properly, causing blood sugar levels to rise. While it was once called “adult-onset diabetes,” it now affects people of all ages, including children, making it one of the most common health challenges worldwide.

Table of contents

• What is Type 2 Diabetes?
• What Causes Type 2 Diabetes?
• Who is at Risk?
• Signs and Symptoms
• How is Type 2 Diabetes Diagnosed?
• Potential Health Problems
• Treatment Options
• Prevention and Lifestyle Changes
• Living with Type 2 Diabetes

What is Type 2 Diabetes?

Type 2 diabetes is a disease that happens when your blood glucose, also called blood sugar, becomes too high^[1]. Blood glucose is your main source of energy and comes from the foods you eat^[5]. A hormone (a chemical messenger in your body) called insulin, which is made by your pancreas, helps glucose get into your cells to be used for energy^[1].

In type 2 diabetes, your body does not use insulin properly—this is called insulin resistance^[1]. At first, your beta cells (special cells in your pancreas) make extra insulin to try to make up for it. Over time, your pancreas cannot make enough insulin to keep your blood glucose at normal levels^[1].

Type 2 diabetes is the most common type of diabetes. About 90% to 95% of people with diabetes have type 2^[3]. More than 37 million people in the United States have diabetes, which is about 1 in 10 people^[4]. The number of people living with diabetes worldwide rose from 200 million in 1990 to 830 million in 2022^[9].

Type 2 diabetes develops most often in middle-aged and older adults but is increasing in young people^[1]. More children, teens, and young adults are developing type 2 diabetes than in the past^[3]. The increase in the number of children with obesity has led to more young people with type 2 diabetes^[2].

What Causes Type 2 Diabetes?

The main cause of type 2 diabetes is insulin resistance^[4]. Insulin resistance happens when cells in your muscles, fat, and liver do not respond normally to insulin^[3]. When your body is not responding to insulin properly, your pancreas has to make more insulin to try to overcome your increasing blood glucose levels. If your cells become too resistant to insulin and your pancreas cannot make enough insulin to overcome it, it leads to type 2 diabetes^[4].

Several factors can contribute to insulin resistance, including genetics, excess body fat especially in your belly and around your organs, physical inactivity, eating highly processed high-carbohydrate foods and saturated fats frequently, certain medications like long-term corticosteroid use, hormonal disorders, chronic stress, and a lack of quality sleep^[4].

Type 2 diabetes may be caused by a combination of factors, including being overweight or having obesity, not being physically active, and genetics and family history^[16]. The cause of type 2 diabetes is complex, but researchers know that genetics play a strong role. Your lifetime risk of developing type 2 diabetes is 40% if you have one biological parent with type 2 diabetes and 70% if both of your biological parents have it^[4].

Who is at Risk?

You can develop type 2 diabetes at any age, even during childhood. However, type 2 diabetes occurs most often in middle-aged and older people^[5]. You are more likely to develop type 2 diabetes if you are age 45 or older^[5].

You are at risk for type 2 diabetes if you^[3]:

• Have prediabetes (blood sugar that is higher than normal but not high enough to be called diabetes)
• Have overweight or obesity
• Are 45 or older
• Have a parent, brother, or sister with type 2 diabetes
• Are physically active less than 3 times a week
• Have ever had gestational diabetes (diabetes during pregnancy) or given birth to a baby who weighed 9 pounds or more
• Are an African American, Hispanic or Latino, American Indian, or Alaska Native person. Some Pacific Islander people and Asian American people are also at higher risk

If you have non-alcoholic fatty liver disease you may also be at risk for type 2 diabetes^[3]. Other risk factors include having other conditions such as high blood pressure, heart disease, stroke, polycystic ovary syndrome, or depression, having low HDL (good) cholesterol and high triglycerides, and having acanthosis nigricans—dark, thick, and velvety skin around your neck or armpits^[6].

Signs and Symptoms

Symptoms of type 2 diabetes often develop slowly over several years and can be so mild that you might not even notice them^[5]. Many people have no symptoms at all^[6]. Some people do not find out they have the disease until they have diabetes-related health problems, such as blurred vision or heart disease^[5].

Common symptoms of diabetes include^[1]:

• Urinating often
• Feeling very thirsty
• Feeling very hungry—even though you are eating
• Extreme fatigue
• Blurry vision
• Cuts or bruises that are slow to heal
• Tingling, pain, or numbness in the hands or feet

Additional symptoms may include unexplained weight loss, dry skin, frequent infections, and slow healing of cuts or sores^[2]. Women may experience frequent vaginal yeast infections and/or urinary tract infections^[4].

How is Type 2 Diabetes Diagnosed?

Your health care provider will use blood tests to diagnose type 2 diabetes^[6]. Simple blood tests can diagnose type 2 diabetes^[4].

The glycated hemoglobin test, also called the A1C test, most often diagnoses type 2 diabetes. It reflects the average blood sugar level for the past two to three months^[10]. Results mean the following^[10]:

• Below 5.7% is healthy
• 5.7% to 6.4% is prediabetes
• 6.5% or higher on two separate tests means diabetes

Other blood tests include^[6]:

The fasting plasma glucose (FPG) test, which measures your current blood sugar level. You need to fast (not eat or drink anything except water) for at least 8 hours before the test. Results are as follows: Less than 100 mg/dL is healthy, 100 to 125 mg/dL is prediabetes, and 126 mg/dL or higher on two tests is diabetes^[10].

The random plasma glucose (RPG) test, which measures your current blood sugar level. This test is used when you have diabetes symptoms and the provider does not want to wait for you to fast before having the test. A level of 200 mg/dL or higher suggests diabetes, especially if you also have symptoms of diabetes such as urinating often and being very thirsty^[10].

The oral glucose tolerance test mainly tests the blood sugar of people who are pregnant and those who have cystic fibrosis. You do not eat for a certain amount of time, then you drink a sugary liquid at your healthcare team’s office. You give blood samples over two hours to test blood sugar levels^[10].

Potential Health Problems

Chronic hyperglycemia (persistently high blood sugar) in combination with the other metabolic problems in patients with diabetes mellitus can cause damage to various organ systems, leading to the development of disabling and life-threatening health complications^[16]. The most prominent complications are microvascular (affecting small blood vessels) complications like retinopathy (eye disease), nephropathy (kidney disease), and neuropathy (nerve disease), and macrovascular (affecting large blood vessels) complications leading to a 2-fold to 4-fold increased risk of cardiovascular diseases^[16].

Over time, high blood sugar levels in type 2 diabetes can damage the eyes, kidneys, nerves, and heart^[2]. High blood sugar is damaging to the body and can cause other serious health problems such as heart disease, vision loss, and kidney disease^[3].

Type 2 diabetes affects all parts of the body and can cause serious, potentially life-threatening complications. These include atherosclerosis (fat buildup in the artery walls that can impair blood flow to all the organs, with the heart, brain, and legs most often affected), retinopathy (damage to tiny blood vessels in the retina that can lead to bleeding and vision loss), kidney disease, nerve damage, and an increased risk of infections^[8].

In 2021, diabetes was the direct cause of 1.6 million deaths, and 47% of all deaths due to diabetes occurred before the age of 70 years. Another 530,000 kidney disease deaths were caused by diabetes, and high blood glucose causes around 11% of cardiovascular deaths^[9].

Treatment Options

There is no cure for type 2 diabetes. However, losing weight, eating well, and exercising can help manage the condition^[2]. If diet and exercise are not enough to manage blood sugar, diabetes medicines or insulin therapy may help^[2].

Treatment for people with type 2 diabetes can include an eating plan, physical activity, and oral or injectable medications (including insulin) to help you meet your target blood glucose levels^[1]. Managing type 2 diabetes involves a comprehensive approach that includes meal planning, regular physical activity, and the right diabetes medications. By combining these three strategies, individuals can effectively regulate their blood glucose levels^[12].

If you need medicine, you will usually be offered metformin, which is one of a few medicines used to treat type 2 diabetes^[17]. Metformin is the first-line treatment option. It is safe and fairly well-tolerated, has excellent long-term effectiveness, is moderately priced, and has a simple dosing regimen^[15].

If metformin alone does not lower your blood glucose level, you may need to take another medicine with metformin or change to a different diabetes medicine^[17]. Many type 2 diabetes medications, including oral and injectable options, work in different ways to regulate blood glucose levels^[12]. Most patients with type 2 diabetes require more than one medication^[15].

If metformin or other diabetes medicines do not help, you may need to take insulin^[17]. You may need to take insulin a few times a day, either by injection or through a pump. This will help keep your blood glucose levels within a normal range. You will be told how much to take and when to take it^[17].

Some people may be able to manage their diabetes with healthy eating and being active, or their doctor may prescribe insulin or other medicines^[3]. You will need to check your blood sugar regularly and have regular appointments with your healthcare team to monitor your condition^[17].

Prevention and Lifestyle Changes

You can prevent or delay type 2 diabetes with proven lifestyle changes^[3]. These include losing weight if you have overweight, eating a healthy diet, and getting regular physical activity^[3].

Losing weight lowers the risk of diabetes. The American Diabetes Association recommends that people with prediabetes lose at least 5% to 7% of their body weight to prevent diabetes^[20]. People in one large study lowered their risk of developing type 2 diabetes by almost 60% over three years by losing about 7% of their body weight with changes in physical activity and diet^[20].

Regular exercise is good for people with diabetes. It lowers blood sugar, improves blood flow, lowers blood pressure, helps burn extra fat so that you can keep your weight down, and helps you handle stress and improves your mood^[23]. Try walking, jogging, or biking for 30 to 60 minutes every day^[23].

A healthy diet includes following a healthy eating plan. Try to eat a healthy diet including fruit, vegetables, wholegrain foods such as wholemeal bread and oats, and pulses such as chickpeas and lentils^[17]. Foods with sugar or carbohydrates can raise your blood sugar too high. A nurse or dietitian can teach you about good food choices. Make sure you know how to have a balanced meal with protein and fiber^[23].

Other important lifestyle changes include stopping smoking (having diabetes increases the harmful effects of smoking), limiting how much alcohol you drink, having regular dental check-ups to help prevent gum disease, and getting enough quality sleep^[17].

Living with Type 2 Diabetes

Type 2 diabetes is a chronic disease that requires long-term medical attention to limit the development of its devastating complications and to manage them when they do occur^[7]. Life does not end with type 2 diabetes—your best days lie ahead^[18].

It takes time and practice to live well with diabetes. Everything you do to take care of yourself helps. Over time, you will learn how to make diabetes fit with the rest of your life^[19]. Managing diabetes can be challenging, but everything you do to improve your health is worth it^[3].

You should have good control of your blood sugar. Learn the basic steps for managing diabetes to stay as healthy as possible. Steps include checking your blood sugar at home, keeping a healthy diet, being physically active, and being sure to take any medicine or insulin as instructed^[23].

Your provider will also help you by ordering blood tests and other tests. These help make sure your blood sugar and cholesterol levels are each in a healthy range. Also, follow your provider’s instructions about keeping your blood pressure in a healthy range^[23].

If you have type 2 diabetes, you will need check-ups to make sure your treatment is working and your condition is being managed. These include checking your average blood glucose levels (an HbA1c test) every 3 to 6 months, a foot check-up once every 2 years if your last check was OK or once a year if you need it, and checking your weight, body mass index, cholesterol, blood pressure, and kidneys at least once a year^[17]. You will also be offered diabetic eye screening when you are diagnosed and reviewed every 1 or 2 years^[17].

Everyone with diabetes should receive proper education and support about the best ways to manage their diabetes. Ask your health care provider about seeing a certified diabetes care and education specialist (often called a diabetes educator)^[23]. Diabetes self-management education and support can help you learn practical skills, gain confidence, and get support^[19].

Making lifestyle changes can be hard, but starting with small changes and building from there may benefit your health. You may want to get help from family, loved ones, friends, and other trusted people in your community^[24].