There are several types of diabetes, not just two. Most people know about Type 1 and Type 2, which together account for the vast majority of cases. But gestational diabetes, LADA, MODY, Type 3c, neonatal diabetes, and drug-induced diabetes are all recognized as distinct forms, each with different causes and different treatment paths. About 40.1 million people in the United States have diabetes, and understanding which type you’re dealing with matters because the management for each one can look completely different.
Type 1 Diabetes
Type 1 diabetes is an autoimmune condition. Your immune system attacks and destroys the cells in the pancreas that produce insulin, leaving your body unable to make it at all. Without insulin, glucose stays in your bloodstream instead of entering your cells for energy. People with Type 1 need to take insulin every day for the rest of their lives, whether through injections or a pump.
About 2.1 million people in the U.S. have diagnosed Type 1 diabetes, including roughly 314,000 children and adolescents. It typically appears in childhood or early adulthood, though it can develop at any age. Because insulin production is essentially absent, a blood test called C-peptide (which measures how much insulin the pancreas is making) will show very low levels. This test helps doctors confirm a Type 1 diagnosis and distinguish it from Type 2.
Type 2 Diabetes
Type 2 is by far the most common form, making up the overwhelming majority of all diabetes cases. It develops through a combination of two problems: your body’s cells stop responding normally to insulin (insulin resistance), and your pancreas gradually loses its ability to produce enough insulin to compensate.
Insulin resistance starts in your muscles, fat tissue, and liver. Excess body fat triggers inflammatory signals and releases fatty acids into the bloodstream, which interfere with your cells’ ability to absorb glucose. In the early stages, your pancreas works harder to keep up, pumping out more insulin. Over time, the insulin-producing cells wear out. In adults, this decline in function happens at a rate of roughly 7% to 11% per year. In younger people with Type 2, the decline is much steeper, at 20% to 35% per year, which is one reason youth-onset Type 2 tends to be more aggressive.
Unlike Type 1, many people with Type 2 can manage their blood sugar through lifestyle changes and oral medications, at least initially. Some eventually need insulin as their pancreas produces less over time.
How Diabetes Is Diagnosed
Regardless of type, diabetes is confirmed using the same blood sugar thresholds. The American Diabetes Association recognizes three main tests:
- A1C: Measures your average blood sugar over the past two to three months. Normal is below 5.7%, prediabetes ranges from 5.7% to 6.4%, and diabetes is diagnosed at 6.5% or higher.
- Fasting blood glucose: Taken after an overnight fast. Normal is below 100 mg/dL, prediabetes is 100 to 125, and diabetes is 126 or higher.
- Oral glucose tolerance test: Measures blood sugar two hours after drinking a glucose solution. Normal is below 140 mg/dL, prediabetes is 140 to 199, and diabetes is 200 or higher.
Once diabetes is confirmed, additional tests like C-peptide levels and autoantibody panels help determine which specific type you have.
Gestational Diabetes
Gestational diabetes develops during pregnancy in people who didn’t have diabetes before. Hormonal changes make your body more resistant to insulin, and if your pancreas can’t keep up with the increased demand, blood sugar rises. It’s typically screened for between weeks 24 and 28 of pregnancy using a glucose tolerance test. A blood sugar reading of 153 mg/dL or higher two hours after drinking the glucose solution points to gestational diabetes.
For most people, blood sugar returns to normal after delivery. But having gestational diabetes significantly raises your risk of developing Type 2 later in life, which is why follow-up testing in the months and years after pregnancy is important.
LADA (Type 1.5 Diabetes)
Latent autoimmune diabetes in adults, often called LADA or Type 1.5, sits between Type 1 and Type 2. Like Type 1, it’s an autoimmune condition where the immune system attacks insulin-producing cells. But it progresses much more slowly, which is why it’s frequently misdiagnosed as Type 2.
LADA generally appears after age 30. The key distinguishing feature is the presence of autoantibodies in the blood, particularly one called GAD65, which shows up in about 90% of LADA cases. People with LADA don’t need insulin right away, typically managing without it for at least six months after diagnosis. Eventually, though, as the autoimmune destruction continues, most will need insulin. If you’ve been diagnosed with Type 2 but aren’t overweight, aren’t responding well to standard medications, or have a family history of autoimmune conditions, LADA is worth investigating.
MODY (Monogenic Diabetes)
Maturity-onset diabetes of the young, or MODY, is caused by a single gene mutation passed down through families. It accounts for a small percentage of all diabetes cases but is important to identify because treatment varies dramatically depending on which gene is affected.
The two most common forms make up nearly all MODY cases. One type (responsible for 50% to 70% of cases) involves a gene that controls how the liver and pancreas regulate blood sugar. People with this form often respond well to a class of oral medications and may not need insulin. The other common type (30% to 50% of cases) involves the gene that acts as the body’s glucose sensor. This form produces mildly elevated blood sugar that’s usually stable and often doesn’t require any treatment at all. Less common forms each account for 5% to 10% of cases.
MODY is often misdiagnosed as Type 1 or Type 2. If you developed diabetes before age 25, have a strong family history spanning multiple generations, and don’t have the autoantibodies associated with Type 1, genetic testing for MODY is worth pursuing. A correct diagnosis can sometimes mean switching from insulin to an oral medication, or stopping treatment entirely.
Type 3c (Pancreatogenic) Diabetes
Type 3c diabetes develops when the pancreas is physically damaged by disease, injury, or surgery. The causes include chronic or acute pancreatitis, pancreatic cancer, cystic fibrosis, iron overload conditions like hemochromatosis, and surgical removal of part or all of the pancreas.
What makes Type 3c distinct from other types is that the damage isn’t autoimmune and isn’t caused by insulin resistance. The pancreas simply can’t function properly because of structural harm. People with Type 3c often have digestive problems too, because the same damage that reduces insulin production also reduces the digestive enzymes the pancreas normally makes.
Researchers estimate Type 3c represents 1% to 9% of all diabetes cases, a wide range because it’s not well recognized and is frequently misdiagnosed as Type 2. If you developed diabetes after a bout of pancreatitis or a pancreatic condition, it’s worth asking your doctor whether Type 3c fits your situation, since management may differ.
Neonatal Diabetes
Neonatal diabetes is a rare genetic form that appears in infants, most often within the first six months of life. It comes in two forms: transient, where the diabetes resolves in infancy but may return later in life, and permanent, where insulin is needed from the start and indefinitely. Which form a child has depends on the specific gene mutation involved. Some children with permanent neonatal diabetes caused by certain mutations can eventually switch from insulin injections to oral medications, which is why genetic testing in infants diagnosed this early is particularly valuable.
Drug-Induced Diabetes
Certain medications can push blood sugar high enough to cause diabetes, especially in people who already have some degree of insulin resistance. This is recognized as its own category by both the WHO and the American Diabetes Association.
Steroids like prednisone are the most common culprits. All glucocorticoids cause dose-dependent insulin resistance, and long-term use leads to impaired blood sugar control or outright diabetes in 14% to 28% of people taking them. Atypical antipsychotic medications, particularly clozapine and olanzapine, are also well-documented triggers. Other medications that can raise blood sugar include certain blood pressure drugs (thiazide diuretics carry a risk of about 3 to 6 new cases per 1,000 patient-years at higher doses, and beta-blockers increase the risk of new diabetes by about 22%), HIV medications, high-dose asthma inhalers, and immunosuppressants used after organ transplants.
In some cases, blood sugar returns to normal when the medication is stopped or the dose is reduced. In others, the drug unmasks diabetes that was already developing, and it persists. If your blood sugar rose after starting a new medication, your doctor can help determine whether the drug is the primary cause or whether an underlying form of diabetes was already in progress.