Types of 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

Diabetes is a chronic disease that causes the level of sugar (glucose) in the blood to be too high when left untreated. A person with diabetes has too little or no insulin, a hormone that helps glucose reach cells to provide energy, or the body is not able to use insulin properly, causing glucose to build up in the blood.

High blood sugar is the main feature of diabetes (measured in a blood test), but there are several distinct types of diabetes that have this telltale sign. Diabetes symptoms sometimes vary between children and adults and among the different types of diabetes, but the different types also share some common symptoms and signs. In many diabetes patients, symptoms will not be apparent until the condition has progressed for years. Symptoms and even lab markers may resemble more than one form of diabetes, which may make diagnosis more difficult.

Therefore, it may sometimes be challenging at first for doctors to pinpoint the type of diabetes right away.

Types of diabetes range from autoimmune-generated diabetes (type 1) to diabetes marked by more gradual insulin resistance (type 2) to diabetes that develops or gets worse as a direct result of pregnancy (gestational diabetes) or other conditions or medications.

Common Diabetes Types

The two most common forms of diabetes are type 1 and type 2.

Type 2 diabetes: The most common type of diabetes in the United States is type 2 diabetes, most often occurring in adults over age 45. However, it is increasingly being diagnosed in younger adults, teenagers and younger children.

The primary cause of type 2 diabetes is a combination of insufficient insulin and insulin resistance — the body’s cells do not respond correctly to insulin, so they are unable to convert blood sugar into energy. To compensate, the pancreas makes even more insulin, and eventually, it is unable to keep up. People with type 2 diabetes may be treated with a combination of lifestyle changes, nutrition, exercise and oral and/or injectable medications (including insulin).

Learn more about type 2 diabetes

Type 1 diabetes: Type 1 diabetes is another form of diabetes that can be found in the United States. It is an autoimmune condition in which the immune system attacks and destroys insulin-producing (beta) cells in the pancreas, resulting in little or no insulin production. It occurs more often in young people — which is why it was once called “juvenile diabetes” — but type 1 diabetes may develop at any age. As with many autoimmune conditions, doctors are not sure what triggers type 1 diabetes, but people with a family history of the disorder may have a higher risk.

As with type 2 diabetes, someone in the early stages of type 1 diabetes may not have obvious symptoms or may have inconsistent symptoms. However, as more insulin-producing cells are destroyed, the condition may quickly become noticeable, and even life-threatening. Type 1 diabetes must always be treated with insulin injections, and many patients use continuous glucose monitors and insulin pumps to manage their insulin and blood sugar levels.

Learn more about type 1 diabetes

Prediabetes

Prediabetes occurs when blood sugar levels are higher than normal, but not yet in the diabetic range. Doctors use fasting blood glucose and A1C blood tests to diagnose prediabetes.

An A1C test measures the amount of sugar-coated hemoglobin in a person’s blood cells. Everyone’s blood contains hemoglobin, a protein that delivers oxygen to tissues, but people with higher blood sugar levels have more sugar-coated hemoglobin. Prediabetes is defined as an A1C of between 5.7% and 6.4%, while diabetes is diagnosed with an A1C of over 6.5%.

An estimated 97.6 million American adults over age 18 had prediabetes in 2021, according to the U.S. Centers for Disease Control and Prevention. That translates to 1 in 3 adults nationwide. Prediabetes is associated with serious health risks like obesity, heart disease and stroke, but it may be reversible with lifestyle and nutrition changes.

Less Common Types

While type 1 and type 2 are the two most common forms of diabetes diagnosed in the United States, numerous other forms of diabetes exist, some of which also have subtypes. The exact symptoms and progressions of each type of diabetes may range widely by type and by person.

Type 3c Diabetes

Type 3c diabetes is a general term that describes diabetes that results from pancreatic diseases and injuries. Because the pancreas is responsible for secreting insulin, any injury or disorder affecting the organ may result in low levels of insulin production.

The most common pancreatic-related conditions that may lead to type 3c diabetes are chronic pancreatitis, pancreatic cancer, cystic fibrosis and surgery. Prevalence for type 3c is unknown.

Gestational Diabetes

Gestational diabetes is a type of diabetes that only occurs during pregnancy in women who do not already have diabetes. While having it does not mean that a patient will have diabetes after pregnancy, both the baby and the mother have an increased risk for developing type 2 diabetes later in life. Gestational diabetes often resolves after the pregnancy.

Gestational diabetes occurs in about 9% of pregnancies, according to the American Diabetes Association. Steps to manage it include lifestyle changes, such as monitoring carbohydrates, being more active, testing blood sugar levels at home and, if needed, taking metformin to help control blood sugar levels. The exact cause is unknown, but it may owe to hormones secreted by the placenta that block the mother’s insulin. The placenta, which nourishes the growing fetus, is an organ present only during pregnancy.

Latent Autoimmune Diabetes in Adults (LADA)

Latent autoimmune diabetes in adults (LADA) has characteristics of both type 1 and type 2 diabetes. LADA may not require insulin therapy at the onset, but patients will become insulin dependent as diabetes progresses.

LADA patients may be misdiagnosed as having type 2 diabetes. People with LADA have antibodies to pancreatic cells that make insulin, which means that the immune system steadily works to destroy those cells because it mistakes them as a threat. In the past, this condition may have been referred to as type 1.5 diabetes.

Maturity Onset Diabetes of the Young (MODY)

Maturity onset diabetes of the young (MODY) tends to develop in young adults under age 25. It is caused by genetic mutations that cause pancreatic beta cell dysfunction.

Like LADA, MODY may be easy to misdiagnose, and symptoms may be difficult to pinpoint in the early stages, especially because it tends to occur in nonobese young adults with no clear signs of insulin resistance. This type of diabetes has at least six recognized subtypes, and genetic testing is recommended to identify each patient’s subtype in order to tailor treatment.

Neonatal Diabetes

Neonatal diabetes is a condition caused by a genetic mutation. Sometimes called congenital diabetes, it causes a baby under six months of age to develop diabetes. It is rare, occurring in 1 in every 90,000 to 160,000 live births, according to a 2018 review in Clinics in Perinatology. Babies with this condition will need insulin therapy for life, although there is some evidence that early diagnosis and aggressive treatment may help preserve function of some pancreatic beta cells.

Steroid-Induced Diabetes

Steroid-induced diabetes occurs when someone who already has diabetes takes corticosteroids, which may elevate blood sugar levels to sometimes dangerous levels. Treatment depends on what the steroids are being used for, the dose someone is taking and what other conditions are present. The care team will take these factors into account when making a tailored management plan.

Cystic Fibrosis Diabetes

Cystic fibrosis-related diabetes (CFRD) is a form of diabetes that develops as a direct result of having cystic fibrosis (CF), a genetic disease that primarily affects the lungs, digestive system and pancreas. About 19% of adolescents and 40% to 50% of adults with cystic fibrosis have CFRD, according to a 2019 review in the Journal of Cystic Fibrosis. New treatments and medications have enabled patients with CF to live longer, which means that they may also develop the typical complications of diabetes. Patients with CFRD will need careful management of the condition to help their overall health as well as complications from CF.

Wolfram Syndrome

Wolfram syndrome is a rare, inherited genetic disorder that affects multiple organs, including insulin-dependent diabetes, vision loss, hearing loss, neurodegenerative disorder and psychiatric disorders.

Alström Syndrome

Alstrӧm syndrome is another very rare genetic disorder that causes type 2 diabetes, among other severe health issues. Symptoms begin in infancy, but progression and presentation of the disease may vary from person to person.

Brittle Diabetes

Now regarded as demeaning to some, the term brittle diabetes was once used by doctors to describe people with diabetes who had very large swings in their blood sugar or frequent, disruptive episodes of either low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia).

Secondary Diabetes in Cancer Patients

Cancer treatment is linked to new-onset diabetes as well as to worsening of preexisting diabetes. There is evidence that some cancer treatments may cause immune-mediated diabetes or type 2 diabetes, especially if they are genetically prone to developing diabetes.