Type 2 Diabetes

January 7, 2025

This page was reviewed under our medical and editorial policy by Ping H. Wang, M.D., professor and chair, Department of Diabetes, Endocrinology & Metabolism, City of Hope^® Cancer Center Duarte

Type 2 diabetes is a common chronic disease in the United States. An estimated 1 in 10 Americans have diabetes, and 90% to 95% of all cases are type 2 diabetes, according to the U.S. Centers for Disease Control and Prevention (CDC).

This guide to type 2 diabetes and its causes, symptoms and treatment options is designed to help patients and their families learn more.

What Is Type 2 Diabetes?

Type 2 diabetes is a disease that occurs when a person’s blood sugar, also called blood glucose, is too high.

Blood sugar mostly comes from food and provides energy. A hormone called insulin, made by the pancreas, is essential for helping blood sugar provide energy. It helps blood sugar go from the bloodstream and into the body’s cells.

When type 2 diabetes occurs, the body either is not using insulin well and/or is not producing enough insulin. As a result, too much glucose remains in the blood, and these high blood sugar levels over time can lead to health problems.

Type 2 Versus Type 1 Diabetes

There are two main types of diabetes, type 1 and type 2. In both types, there is too much glucose in the blood and insulin is not being produced in normal amounts.

There are, however, key differences between the two types. Type 1 is an autoimmune disease in which the pancreas is unable to produce insulin. Type 1 diabetes is less common and most often is diagnosed in children and young adults.

Type 2 diabetes is more common in adults. It occurs when the body becomes resistant to insulin over time. In other words, the cells are not able to respond to insulin and take in sugar for energy. At first, the pancreas tries to release extra insulin, but over time, the pancreas begins to produce less insulin.

Type 2 Diabetes Symptoms

Type 2 diabetes does not always cause symptoms, and when symptoms do occur, they often develop very slowly.

The symptoms most often associated with type 2 diabetes may include:

• Fatigue
• Blurry vision
• Increased hunger and thirst
• More frequent need to urinate
• Tingling or numbness in the feet or hands
• Weight loss without explanation
• Sores or cuts that heal slowly or not at all

However, many of these symptoms may be caused by factors other than type 2 diabetes, so patients should always talk with their doctor to find out more.

What Causes Type 2 Diabetes?

Type 2 diabetes is caused by several complex factors that make a person’s cells resistant to insulin. Insulin is made by the pancreas, but if blood sugar levels continue to rise over time, the pancreas may not be able to produce enough insulin.

This is known as insulin resistance, and it means the body’s cells are no longer able to absorb sugar. Over time, blood sugar levels may become too high, leading to type 2 diabetes.

Many risk factors make a person prone to insulin resistance and type 2 diabetes, including some gene variations and personal factors, like being overweight.

Risk Factors

Risk factors are things that may increase a person’s likelihood of developing a disease. For type 2 diabetes, risk factors linked to the disease may include:

• Being 45 or older
• Family history of diabetes
• Being overweight
• Lack of regular physical exercise
• Certain ethnicities (African Americans, Alaska Natives, American Indians, Asian Americans, Hispanics/Latinos, Native Hawaiians and Pacific Islanders) have an increased risk

Health conditions linked to a higher risk of developing type 2 diabetes may include:

• History of gestational diabetes
• Stroke
• Heart disease and high blood pressure
• Low HDL (good) cholesterol
• Having prediabetes, which means a patient has increased blood sugar levels but not high enough to be classified as diabetes

Is Type 2 Diabetes Genetic?

Type 2 diabetes has a genetic link. Hundreds of genetic variations have been linked so far to type 2 diabetes. However, it is a complex disease that is linked to both genetics and lifestyle factors. Researchers have identified gene changes, which are passed down from parents, that are linked to an increased risk. It is also more common in certain ethnicities and runs in families, pointing to genetic links.

However, there is no clear pattern of inheritance. Instead, it is believed that both genetic changes and lifestyle factors, such as weight and lack of activity, play an important role in the development over time of type 2 diabetes.

How to Prevent Type 2 Diabetes

It may be possible for patients to prevent or delay type 2 diabetes from developing by making certain lifestyle changes. These may include:

• Maintaining a healthy weight
• Getting regular exercise
• Quitting smoking
• Eating a balanced and nutritious diet, such as the diabetes-friendly diet

Patients may wish to speak with their doctor for help in making lifestyle changes.

The Diagnosis Process

If a doctor suspects that the patient has type 2 diabetes, they may perform a series of blood tests to test their blood sugar levels. Blood tests are the only way to confirm a diagnosis of type 2 diabetes.

Diagnostic blood tests for diabetes include the following.

Fasting plasma glucose (FPG) test: Doctors use this blood test to measure the patient’s current blood sugar levels. The patient may need to avoid eating or drinking before the test.

Random plasma glucose (RPG) test: This test also measures the patient’s current blood sugar levels. It is most often used with patients who already have diabetes symptoms.

A1C (also called hemoglobin A1C test, or HbA1C): Used to test for both type 2 and prediabetes, AlC measures the patient’s blood sugar levels over a three-month period.

Type 2 Diabetes Treatments

Treatment for type 2 diabetes is about controlling the patient’s blood sugar levels. This may be achieved through a combination of lifestyle changes and medication, if needed.

Type 2 diabetes may be managed and controlled with the following approaches.

Regular blood sugar and screening tests: Patients with diabetes learn how to regularly test their own blood sugar levels, and some patients may be eligible to use diabetes monitoring devices to help with this process. Patients also undergo regular cholesterol and blood pressure tests. 

Lifestyle changes: Many patients find they are able to better manage their type 2 diabetes by making healthy changes to their diet and increasing their weekly physical exercise.

Medication: Various oral or injectable medications may also be used to manage diabetes.

Type 2 Diabetes Medications

Some patients may need medication to control their type 2 diabetes if they are not able to reduce blood sugar levels through lifestyle changes. 

There are many types of diabetes treatment medications, with each working in slightly different ways. These are some of the most common medication options for type 2 diabetes.

Bromocriptine: This medication is a dopamine receptor that may help lower blood sugar. 

Gliflozins: These help reduce blood glucose levels through urination. When taking this medication, an increased amount of sugar exits the body in urine.

Glinides: This type of drug stimulates the patient’s insulin production.

Gliptins: This medication type also stimulates insulin production.

Glitazones: This helps insulin in the body work better.

Glucagon-like peptide-1 (GLP-1) receptor agonists: This class of medications stimulates insulin secretion, reduces appetite and food intake, and decreases body weight.

Insulin: More commonly used by type 1 diabetes patients, insulin is sometimes used for type 2 patients when other medications are not successful.

Metformin: This medication is often the first option used for type 2 diabetes. It works to reduce the body’s blood sugar levels.

Sulfonylureas: These are used to help increase insulin production.

Can Type 2 Diabetes Be Reversed?

While type 2 diabetes is not curable, it is possible to reverse the disease, bringing down the patient’s blood sugar to normal levels. This is achieved through weight loss and lifelong dietary changes, allowing patients to live without requiring medication.

The patient’s medical team will be able to provide guidance on making lifestyle changes or on medical therapies that may help the patient move toward reversal, also known as remission.

Type 2 Diabetes Complications

If type 2 diabetes is left untreated, it may cause other serious health conditions over a long period of time. These are known as diabetes complications. The complications associated with type 2 diabetes may include:

• Heart disease
• Stroke
• Kidney disease or failure
• Gum disease
• Vision problems, including blindness
• Depression
• Foot problems like numbness, pain and wounds that won’t heal
• Diabetic neuropathy (nerve damage)
• Skin infections
• Immune system weakness
• Sexual issues like erectile dysfunction in men and low desire in women
• Bladder issues like urinary incontinence (involuntary urination)
• Sleep apnea

For patients diagnosed with type 2 diabetes, their care team will discuss the potential complications, along with strategies for reducing their risk.

Type 2 Diabetes Life Expectancy

Having type 2 diabetes may impact a person’s life expectancy, but the good news is that treatment and lifestyle changes may help patients live longer and enjoy a higher quality of life.

According to the CDC, a 2022 study in Diabetes and Endocrinology showed that, at the age of 50, it is estimated that patients with type 2 diabetes in the United States live six years less than those without the disease. However, by working with their doctor to reduce their weight, cholesterol and blood pressure, along with managing their blood sugar, patients may help increase their life expectancy between three to 10 years, researchers found.

Patients should speak with their endocrinology care team to get a prognosis tailored to their specific type 2 diabetes diagnosis.