Most people know about Type 1 and Type 2 diabetes, but there are actually several distinct types, each with different causes and treatments. As of 2024, diabetes affects roughly 589 million adults worldwide, about 11% of the global adult population. Understanding which type you or someone you know has matters because the treatment approach can be completely different.
Type 1 Diabetes
Type 1 diabetes is an autoimmune disease. Your immune system mistakenly attacks and destroys the insulin-producing cells in your pancreas. Without these cells, your body can’t make insulin at all, so blood sugar builds up with no way to get into your cells for energy. People with Type 1 always need insulin, either through injections or a pump, for the rest of their lives.
Type 1 is most often diagnosed in children and young adults, though it can appear at any age. The exact trigger isn’t fully understood, but it involves a combination of genetic susceptibility and environmental factors. It accounts for roughly 5 to 10% of all diabetes cases. Symptoms tend to come on quickly: extreme thirst, frequent urination, unintended weight loss, and fatigue that doesn’t improve with rest.
Type 2 Diabetes
Type 2 is by far the most common form, making up about 90 to 95% of all diabetes cases. It develops when your body’s cells stop responding normally to insulin, a problem called insulin resistance. Your pancreas tries to compensate by producing more insulin, but over time it can’t keep up. The result is the same as Type 1 (too much sugar in the blood) but the underlying problem is different.
Obesity is the most common driver of insulin resistance. Excess body fat interferes with the way your cells receive insulin’s signal to absorb sugar. Type 2 typically develops gradually, often over years, and many people have no obvious symptoms in the early stages. It’s most frequently diagnosed in adults over 40, but rising obesity rates have made it increasingly common in younger people, including teenagers. Unlike Type 1, many people with Type 2 can manage it through lifestyle changes, oral medications, or a combination of both, though some eventually need insulin as their pancreas produces less over time.
Prediabetes
Prediabetes isn’t a separate “type” of diabetes, but it’s a critical stage that often precedes Type 2. It means your blood sugar is higher than normal but not yet high enough for a diabetes diagnosis. According to the American Diabetes Association, prediabetes is defined as an A1C between 5.7% and 6.4%, a fasting blood sugar of 100 to 125 mg/dL, or a two-hour glucose tolerance reading of 140 to 199 mg/dL. A diabetes diagnosis starts at an A1C of 6.5%, a fasting glucose of 126 mg/dL, or a two-hour reading of 200 mg/dL or higher.
The reason prediabetes matters: it’s often reversible. Modest weight loss (even 5 to 7% of body weight), regular physical activity, and dietary changes can bring blood sugar back to normal levels and prevent or significantly delay the progression to Type 2.
Gestational Diabetes
Gestational diabetes develops during pregnancy in people who didn’t have diabetes before. Hormones produced by the placenta can make your cells more resistant to insulin, and if your pancreas can’t produce enough extra insulin to overcome that resistance, blood sugar rises. It’s typically screened for between 24 and 28 weeks of pregnancy, though people at high risk may be tested at their first prenatal visit.
Screening involves drinking a sugary solution and then having your blood drawn. A one-hour reading below 140 mg/dL is generally considered normal. A reading of 190 mg/dL or higher indicates gestational diabetes. If the result falls between those values, a longer follow-up test checks blood sugar at one, two, and three hours after drinking a more concentrated glucose solution. Two or more elevated readings on that test confirm the diagnosis.
Gestational diabetes usually resolves after delivery, but it significantly increases the risk of developing Type 2 diabetes later in life. It can also lead to complications during pregnancy if blood sugar isn’t well controlled, including a larger-than-average baby and increased likelihood of cesarean delivery.
LADA (Type 1.5 Diabetes)
Latent autoimmune diabetes in adults, often called LADA or Type 1.5 diabetes, shares features of both Type 1 and Type 2. Like Type 1, it involves an autoimmune attack on the insulin-producing cells in the pancreas. But like Type 2, it develops slowly, typically in adults over 30, and doesn’t require insulin right away.
LADA is frequently misdiagnosed as Type 2 because it appears in adults and progresses gradually. The key difference is that people with LADA produce autoantibodies, the same immune markers found in Type 1. Over time, usually within 5 to 10 years of diagnosis, most people with LADA will need insulin as their pancreas loses the ability to produce it. Recognizing LADA early matters because treatments designed for Type 2 (which focus on reducing insulin resistance) don’t address the autoimmune destruction that’s the real problem.
MODY (Maturity-Onset Diabetes of the Young)
MODY accounts for about 1 to 2% of diabetes cases and is caused by a mutation in a single gene. Because it follows a dominant inheritance pattern, a parent with MODY has a 50% chance of passing it to each child. It typically develops before age 25.
There are several subtypes of MODY, and the distinction matters because each one responds to different treatments. Some forms are mild enough that they need no medication at all. Others respond well to oral medications, and only a few require insulin. MODY is often misdiagnosed as Type 1 or Type 2 because it’s rare and many clinicians don’t test for it. Genetic testing is the only way to confirm a MODY diagnosis.
Type 3c Diabetes
Type 3c diabetes results from physical damage to the pancreas rather than an autoimmune attack or insulin resistance. Any condition that harms the pancreas can cause it: chronic or acute pancreatitis, pancreatic cancer, cystic fibrosis, iron overload (hemochromatosis), or surgical removal of part or all of the pancreas.
What sets Type 3c apart is that the damage often affects more than just insulin production. The pancreas also makes digestive enzymes, so people with Type 3c frequently have trouble digesting food properly, especially fats. Treatment depends on how much of the pancreas is still functioning. Some people manage with oral medications alone, while others need insulin. Most also need to take enzyme supplements with meals to aid digestion.
Drug-Induced and Secondary Diabetes
Certain medications can push blood sugar high enough to cause diabetes. Antipsychotic medications are among the most well-known culprits, partly because they promote weight gain and disrupt how the body handles sugar. Some older HIV medications, particularly certain antivirals, also increase insulin resistance. Specific cancer treatments can trigger hyperglycemia as well. These drugs can raise blood sugar through several different mechanisms: increasing insulin resistance, boosting sugar production by the liver, or directly impairing the pancreas’s ability to release insulin.
Hormonal conditions can also cause diabetes. Disorders that lead to excess cortisol or growth hormone production force the body to pump out more glucose than insulin can handle. In some cases, treating the underlying condition or switching medications resolves the blood sugar problem. In others, the diabetes becomes permanent and requires ongoing treatment.
Diabetes Insipidus Is Not the Same Condition
Despite sharing the word “diabetes,” diabetes insipidus is an entirely different disease. Both conditions cause excessive thirst and urination, which is why they were historically grouped under the same name. But the similarity ends there. Diabetes mellitus (all the types described above) involves problems with blood sugar regulation. Diabetes insipidus involves the kidneys’ inability to properly concentrate urine, usually due to a problem with a hormone that controls water balance. Blood sugar levels in diabetes insipidus are completely normal. The two conditions have different causes, different tests, and different treatments.