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What Is Diabetes?

Diabetes is a chronic condition that affects how the body converts food into energy. The body breaks down the food we eat into glucose, a type of sugar. When glucose enters the bloodstream, the pancreas releases the hormone insulin. Insulin pushes sugar into the body's cells so that they can make energy.1

With diabetes, however, the body either can't make enough insulin or doesn’t use the insulin produced efficiently. In both situations, too much sugar ends up in the bloodstream. Over time, this can cause health complications, such as eye, kidney, and heart problems.1


Prevalence of Diabetes

In 2022, 37.3 million people in the United States had diabetes,2 and it is becoming more widespread. There's no cure for diabetes, but treatment and management are possible.1

Causes and Risk Factors

What Causes Diabetes?
Causes of Diabetes

Causes of diabetes depend on the type of diabetes. However, lifestyle factors can predispose some people to the disease.1

Evidence suggests that Type 1 diabetes stems from an autoimmune reaction. The reaction damages the beta cells in the pancreas, which are responsible for insulin production.3

Sometimes it takes months before a person notices Type 1 diabetes symptoms, but usually, when symptoms begin, they quickly become severe.3

The risk factors for Type 1 diabetes are murky compared to those of type 2 diabetes. Family genetics may play a role for some people, but the development of type 1 diabetes isn’t consistent or predictable. An environmental trigger, like a virus, may also contribute to Type 1 diabetes.3

While there is uncertainty about genetic and viral underpinnings of Type 1 diabetes, there is no evidence that indicates that diet and lifestyle choices cause the disease.3

Research has revealed more about the origins of Type 2 diabetes. While lifestyle factors such as diet and exercise, as well as being overweight, are contributors to the disease, so are age, race, and ethnicity. Family history, or genetics , plays a stronger role in the risk for type 2 diabetes than for type 1.9,10

Diabetes Prevention

No one can prevent Type 1 diabetes. However, people can take steps to potentially prevent Type 2 diabetes.3

People who are diagnosed with prediabetes and are overweight can lose anywhere from 5% to 7% of their body weight to reduce their risk of developing Type 2 diabetes. Physical activity and dietary modifications can help. The CDC recommends 150 minutes weekly of up-tempo activity, such as brisk walking. That translates to 30 minutes daily, most days of the week.7

People who are concerned about developing Type 2 diabetes, regardless of whether they have a prediabetes diagnosis, should talk to their healthcare provider and may also turn to the CDC’s Diabetes Prevention Program (DPP), which provides a registry of recognized diabetes prevention programs across the U.S.

The DPP recommendations, including maintaining at least 7% weight loss and exercising at least 150 minutes weekly, were tested in a study. Its findings suggested that these actions reduced diabetes development. The DPP trial’s dietary guidance emphasized eating fewer calories and taking an individualized approach to selecting calorie sources, including carbohydrates, proteins, and fats. Some dietary approaches that may be useful for people at risk of diabetes include a Mediterranean-style diet, a largely plant-based diet, or the DASH diet (which stands for Dietary Approaches to Stop Hypertension).11

For exercise, the DPP trial involved moderate-intensity activity, like brisk walking, as well as resistance training, like lifting weights, to lower diabetes risk. Overall, the trial helped participants moderately reduce levels of blood glucose after a meal.11

With Type 1 diabetes, the beta cells in the pancreas, which make insulin, are destroyed by the immune system. Over time, the amount of insulin the pancreas produces will go down until there’s virtually no insulin in the body. Consequently, blood sugar can't enter the cells for energy production. Instead, it accumulates in the bloodstream, and can cause critical illness if symptoms are not diagnosed.1 Although it can develop at any age, Type 1 diabetes is typically diagnosed in children, teens, and young adults.1

Between 90% and 95% of people in the United States with diabetes have Type 2 diabetes.3 In this version of the disease, even though the pancreas is still making insulin, the body doesn’t use insulin normally. Eventually glucose levels in the blood go up.3 Type 2 diabetes typically occurs in adulthood, and it may take longer to diagnose. This delay is because hyperglycemia, the medical term for high blood sugar, is often not severe enough to generate symptoms early in the disease’s progression.1,4 These symptoms can include feeling hungry or thirsty and frequent urination. Type 2 diabetes increases the risk of heart disease, kidney disease, and certain types of eye disease.1,4

Increasingly, young adults, teens, and children are developing Type 2 diabetes, a trend driven by rising childhood obesity rates.3,5

Gestational diabetes occurs in anywhere between 2% and 10% of pregnancies in the United States. Hormonal changes and weight gain during pregnancy tax the body’s ability to use insulin, sometimes leading to insulin resistance. Some insulin resistance during later stages of pregnancy is normal. But when the body can’t produce enough insulin to keep up, gestational diabetes can occur. A person does not need to have diabetes prior to pregnancy to develop gestational diabetes; however, having insulin resistance prior to pregnancy increases the risk.6

A person with prediabetes has blood sugar levels that are elevated but aren’t high enough to meet the diagnostic criteria for Type 2 diabetes. This situation applies to about 96 million American adults, or more than one in three. Complicating matters, more than 80% aren’t aware that they have prediabetes.7

Many people who develop prediabetes have insulin resistance first. Insulin resistance means that a specific group of cells in the pancreas, called beta cells, produce insufficient insulin to keep blood sugar inside the normal range.8 In prediabetes, the pancreas usually releases more insulin as cells fail to respond to the hormone. But eventually the pancreas falls behind, allowing blood sugar to rise more.7

Diabetes Symptoms

The type, severity, and time to onset of diabetes symptoms can vary depending on the type of diabetes.1

Diabetes Symptoms
  • The symptoms of diabetes may develop over years, making them difficult to notice. In type 2 diabetes, symptoms usually begin in adulthood, but teens and children are increasingly experiencing these symptoms.12 They include:12

    • Frequent urination
    • Increased thirst 
    • Frequent hunger
    • Blurry vision 
    • Numb or tingling feet or hands 
    • Fatigue 
    • Dry skin 
    • Slow-healing sores 
    • An increase in the number of infections
    • Unexplained or unintended weight loss
  • Type 1 diabetes symptoms are largely the same, aside from timing and severity. Onset occurs typically in childhood, but it can begin in teenage or young-adult years. Symptoms usually are sudden—building over a few weeks —and severe.12 In addition to the list above, they include:12

    • Stomach pain
    • Nausea
    • Vomiting

    A Type 1 diabetes diagnosis may stem from the onset of diabetic ketoacidosis (DKA). In one study, 29% of patients had DKA at the time of diagnosis.13 When the body lacks sufficient insulin, it starts using fat as a source of energy. The liver begins to metabolize fat to fuel the body. This process produces ketones, which can accumulate in the blood and reach hazardous levels. When this syndrome develops, it’s called DKA. People with DKA may experience rapid breathing, dry mouth and skin, flushing of the face, abdominal pain, nausea, vomiting, fatigue, muscle aches or stiffness, headache, and breath that smells fruity.14

  • This type of diabetes, which occurs during pregnancy, does not typically have symptoms. That’s why it’s critical that a doctor tests for gestational diabetes between week 24 and week 28 of pregnancy. Early intervention can protect the health of the parent and baby.12

  • Prediabetes often lacks symptoms. That’s why it’s essential for people with the following risk factors to discuss blood sugar testing with their healthcare provider:7

    • Overweight
    • Age 45 or older
    • Fewer than three sessions of physical activity weekly
    • Gestational diabetes
    • Polycystic ovary syndrome 

Common Diabetes Complications

Diabetes raises the risk of multiple complications. But with proper treatment, it's possible to prevent or delay the onset of these conditions:

Common Diabetes Complications
  • Changing fluid levels and swollen tissues can damage the blood vessels of the eyes.15 Diabetic retinopathy is one common complication that can lead to blindness as blood vessels in the retina become damaged. Diabetes can also lead to diabetic macular edema, a condition in which the retina’s blood vessels leak fluid into the macula, another part of the eye necessary for crisp vision. People with diabetes may also experience glaucoma (a cluster of eye diseases that damage the optic nerve) and cataracts (a clouding of the eye’s lens).16

  • Diabetes can lead to nerve damage and diminished blood flow to the feet.15 Nerve damage can lead to a loss of sensation in the feet. This can become problematic when someone has a cut, blister, or ulcer (sore) on their foot. They may not realize they have the wound, which later becomes infected. It could turn into gangrene, and infections may not heal, which can require amputation.17

  • High blood sugar can promote an overgrowth of bacteria in the mouth. These bacteria can lead to plaque buildup, which can cause bad breath, gum disease, tooth decay, and cavities.15 Diabetes, as well as some diabetes medications, may also lower the amount of saliva that a person’s salivary gland produces. With less saliva to wash away food and prevent bacteria growth, people are more susceptible to cavities, gum disease, and other oral health issues.18

  • Diabetes can damage nerves and blood vessels throughout the body, including in the heart.15 People with diabetes have a higher risk of several types of heart disease, including coronary artery disease.19 Diabetes also increases the risk of stroke.19 People who have diabetes also face an increased likelihood of high blood pressure or high cholesterol, which increase their odds of a heart attack or stroke.19

  • Diabetes can harm the blood vessels of the kidneys, as well as nephrons, the parts of the kidney that are responsible for filtering the blood.15,20 Diabetic nephropathy is a common cause of kidney failure and the need for dialysis.15,20

  • High glucose affects the nerves and the blood vessels that supply the nerves with nutrients and oxygen.15 Symptoms may include numbness in the feet, legs, or hands; shooting pains, burning, or tingling sensations; nausea, vomiting, constipation , or diarrhea; or dizziness occurring when changing positions quickly.21

  • Nerve damage and reduced blood flow can lead to both issues.15 Some may experience erectile dysfunction or retrograde ejaculation, a condition in which some semen moves into the bladder instead of out of the penis. Others may have penile curvature, known as Peyronie’s disease. Diabetes can also contribute to fertility problems. Finally, some people may experience bladder leakage, or the inability to fully empty the bladder.22

  • Reduced circulation and changes to small blood vessels can cause skin problems and skin infections.15 People with diabetes may experience more bacterial infections, such as styes, boils, folliculitis, carbuncles, and infections of the nails. They also may have more fungal infections, such as jock itch, athlete’s foot, ringworm, and vaginal infections. Itching stemming from poor circulation, dry skin, or yeast infections is also common.23

For those who have been diagnosed with diabetes, treatment is available. A doctor can help to identify the best diabetes treatment and management options.

Insulin therapy is critical for people with Type 1 diabetes. Along with high blood sugar, insufficient insulin levels can lead to ketoacidosis, and the breakdown of bodily tissues, and high triglycerides.24

Mounting evidence supports multiple daily glucose injections or the use of continuous glucose infusion from an insulin pump. Both approaches have led to improved long-term health and lower A1C levels.24

Pancreas transplantation and islet (insulin-producing cell) transplantation may be options for patients meeting certain criteria. Eligible people may include those who simultaneously receive a kidney transplant, those who recently received a kidney transplant, and those with recurring ketoacidosis or severe low blood sugar despite intensive management.24

Recent research has suggested that islet  transplantation could be successful in long-term management of Type 1 diabetes.25 In islet transplantation, surgeons inject donor cells into a vein, which carries blood to the recipient’s liver. The cells could help the recipient produce and release more insulin.26

People with Type 1 diabetes may also benefit from nutritional therapy. A trained therapist can help them match carbohydrate intake, activity level, and insulin therapy. Meeting the goal of 150 minutes of weekly physical activity may also be beneficial.27

Management of Type 2 diabetes hinges on several factors, including the presence of other diseases, such as cardiovascular disease, and the patient’s circumstances and preferences. Lifestyle changes, such as diet modification and exercise, are often components of Type 2 diabetes management.24

Like Type 1 diabetes, insulin may be involved in Type 2 diabetes management, particularly short-term use for patients who are exhibiting glucose toxicity. In recent years, there has been a shift towards using other newer medications that may have cardiovascular benefits, kidney benefits, and lower risk of certain side effects.24

In addition to insulin, there are other first-line medications a physician may prescribe to manage type 2 diabetes. Depending on the other medical conditions and the patient’s preferences and situation, preferred options include:

  • Biguanides.24 These drugs  work to regulate the amount of glucose produced by the liver, help the body respond to insulin, and increase the amount of glucose absorbed in the intestines.28,29
  • Glucagon-like peptide-1 receptor agonists.24 This class of medications can help promote insulin secretion and has effects in the brain and GI tract.30
  • Sodium-glucose cotransporter 2 inhibitors.24 These drugs lower blood sugar levels by promoting extra glucose to be secreted in the urine.31

Global Impact of Diabetes

Global Impact of Diabetes

The global impact of diabetes is expanding, according to the International Diabetes Federation. As of 2021, the most recent year for which data is available, about 537 million adults between the ages of 20-79 are living with diabetes. The total is projected to reach 643 million by 2030 and 783 million by 2045.32

Three-quarters of adults with diabetes live in low- and middle-income countries.33 Roughly half of all adults with diabetes (about 240 million) are undiagnosed.33

Globally, diabetes and its complications caused about 6.7 million deaths in 2021. The disease also cost an estimated $966 billion that same year. Diabetes alone accounts for 9% of global health costs for adults.33

Nearly 1.2 million children and teens worldwide have Type 1 diabetes, and gestational diabetes affects one in six live births.33

Frequently Asked Questions About Diabetes

  • For years, Type 2 diabetes was considered irreversible, but new research suggests that it can go into remission using approaches geared toward weight loss, including surgery, lifestyle changes, and medications.34 The disease can be treated with a healthy diet, physical activity, and medications. Diabetes treatment may involve monitoring blood glucose levels, receiving patient education, regular visits with healthcare providers, sticking to a healthy nutrition plan under a dietician’s guidance, and attending to the health of feet and eyes.35 Stress management may also be a component of treatment.36

  • There is a strong genetic link with Type 2 diabetes, but it doesn't guarantee that the condition will develop. Lifestyle choices significantly impact the risk. If one parent has Type 2 diabetes, the lifetime risk is 40%. If both parents have it, the risk is 70%.37

  • People who have diabetes that is controlled by insulin or medications can donate blood. Using insulin does not affect eligibility.38

  • Type 1 diabetes cannot be cured, but it can be treated and managed.39 Islet transplantation may also provide long-term management of Type 1 Diabetes.25 Research demonstrates that Type 2 diabetes can be reversed with interventions including diet, reducing carbohydrate intake, and bariatric surgery.34,40

  • Low carbohydrate diets, such as the keto diet, can lead to weight loss and help lower blood sugar. The keto diet may not be appropriate for everyone, especially people with Type 2 diabetes.40 Talking to a doctor or dietitian can be helpful for someone who is interested in a specific diet.35

Find a Pfizer clinical trial for diabetes at

Explore diabetes clinical trials at

Area of Focus: Internal Medicine

Diabetes is a focus of Pfizer’s Internal Medicine Therapeutic Area. Visit the Internal Medicine Page.

The information contained on this page is provided for your general information only. It is not intended as a substitute for seeking medical advice from a healthcare provider. Pfizer is not in the business of providing medical advice and does not engage in the practice of medicine. Pfizer under no circumstances recommends particular treatments for specific individuals and in all cases recommends consulting a physician or healthcare center before pursuing any course of treatment.