There are several types of diabetes, not just the two most people know about. Type 1 and type 2 account for the vast majority of cases, with type 2 alone representing more than 95% of all diabetes diagnoses worldwide. But gestational diabetes, latent autoimmune diabetes in adults (LADA), monogenic diabetes, and type 3c diabetes are distinct conditions with different causes, and recognizing which type someone has changes how it’s treated.
Type 1 Diabetes
Type 1 diabetes is an autoimmune condition. The immune system attacks and destroys the insulin-producing cells in the pancreas, leaving the body unable to make insulin at all. Without insulin, glucose builds up in the bloodstream instead of entering cells for energy. People with type 1 need insulin from the day of diagnosis and for the rest of their lives.
Type 1 most commonly appears in childhood or adolescence, though it can develop at any age. It accounts for roughly 5% of all diabetes cases. The onset tends to be rapid, with symptoms like extreme thirst, frequent urination, unexplained weight loss, and fatigue developing over days or weeks. The exact trigger isn’t fully understood, but genetics and environmental factors both play a role.
Type 2 Diabetes
Type 2 diabetes develops when the body still makes insulin but can’t use it effectively, a problem called insulin resistance. Over time, the pancreas struggles to keep up with the increased demand and insulin production declines. This is the most common form by far, making up over 95% of diabetes cases globally.
Unlike type 1, type 2 develops gradually, often over years. Risk factors include carrying excess weight (particularly around the abdomen), physical inactivity, family history, and age over 45. It’s increasingly diagnosed in younger adults and even adolescents, largely driven by rising obesity rates. Many people have type 2 for years before symptoms become noticeable, which is why routine screening matters. An A1C blood test of 6.5% or above indicates diabetes, while a result between 5.7% and 6.4% falls in the prediabetes range, meaning blood sugar is elevated but not yet high enough for a diabetes diagnosis.
Treatment typically starts with lifestyle changes and oral medications. Some people with type 2 eventually need insulin, but many manage their blood sugar without it for years or even decades.
Prediabetes
Prediabetes isn’t a separate type of diabetes, but it’s a critical stage that precedes type 2. An A1C between 5.7% and 6.4% signals that blood sugar regulation is already impaired. Without intervention, a significant percentage of people with prediabetes progress to type 2 within five to ten years. The encouraging part is that lifestyle changes at this stage, particularly modest weight loss and regular physical activity, can delay or prevent that progression entirely.
Gestational Diabetes
Gestational diabetes develops during pregnancy in people who didn’t have diabetes before. Hormonal changes during pregnancy naturally increase insulin resistance, and when the pancreas can’t compensate, blood sugar rises. Screening typically happens between 24 and 28 weeks of pregnancy, though people with higher risk factors may be tested at the first prenatal visit.
The initial screening involves drinking a glucose solution and having blood drawn an hour later. A blood glucose reading of 140 or higher triggers a follow-up test, while a reading of 200 or higher may indicate pre-existing type 2 diabetes. The follow-up oral glucose tolerance test involves fasting overnight, then having blood drawn at multiple intervals after drinking glucose. Elevated readings at two or more time points confirm gestational diabetes.
Gestational diabetes usually resolves after delivery, but it significantly raises the risk of developing type 2 diabetes later in life. It also increases the chance of complications during pregnancy, including higher birth weight and preterm delivery, which is why managing blood sugar during those months matters.
LADA (Type 1.5 Diabetes)
Latent autoimmune diabetes in adults, sometimes called type 1.5 diabetes, is an autoimmune form that progresses slowly. Like type 1, the immune system attacks the insulin-producing cells in the pancreas. But unlike type 1, the destruction happens gradually over months or years rather than weeks, which means people with LADA often look like they have type 2 diabetes at first.
The initial presentation is similar enough to type 2 that many people with LADA are misdiagnosed. The clue often comes when oral medications stop working. At that point, a blood test for GAD antibodies (proteins that indicate autoimmune activity against the pancreas) can confirm the diagnosis. A C-peptide test, which measures how much insulin the pancreas is still producing, helps gauge how far the condition has progressed. People with LADA eventually need insulin, but the timeline varies. Some manage on oral medications for years before making the switch.
Monogenic Diabetes (MODY)
Maturity-onset diabetes of the young, or MODY, is caused by a single gene mutation rather than the complex mix of genetic and environmental factors behind type 1 or type 2. It’s inherited in a dominant pattern, meaning a child needs only one copy of the mutated gene from one parent to develop it. MODY accounts for a small fraction of all diabetes cases, but it’s frequently misdiagnosed as type 1 or type 2 because it’s not widely screened for.
At least 14 subtypes of MODY have been identified, each linked to a different gene. Two subtypes make up the large majority of cases. The most common, caused by mutations in the HNF1A gene, accounts for 50 to 70 percent of all MODY cases. The second most common, caused by mutations in the GCK gene, accounts for 30 to 50 percent. Both genes are involved in how the pancreas produces insulin, but they affect blood sugar differently. GCK-MODY causes mildly elevated blood sugar that is stable and rarely needs treatment beyond monitoring. HNF1A-MODY causes progressively higher blood sugar that responds well to certain oral medications, often without the need for insulin.
Getting the specific subtype right matters because treatment varies dramatically. Some forms of MODY respond to low-dose oral medication, while others require insulin. People with GCK-MODY may need no medication at all. Genetic testing is the only way to confirm MODY and identify the subtype.
Type 3c (Pancreatogenic) Diabetes
Type 3c diabetes develops when the pancreas is physically damaged enough that it can no longer produce adequate insulin. Unlike the autoimmune destruction in type 1, the damage here comes from disease, injury, or surgery affecting the pancreas itself.
Chronic pancreatitis is the leading cause, responsible for roughly 79% of type 3c cases. Pancreatic cancer accounts for about 8%, and hemochromatosis (a condition where excess iron accumulates in organs, including the pancreas) causes about 7%. Cystic fibrosis contributes around 4% of cases, and surgical removal of part or all of the pancreas makes up about 2%. Because the damage also affects the cells that produce digestive enzymes, people with type 3c often deal with digestive problems alongside their blood sugar issues, a combination that can make the condition harder to manage than other types.
Type 3c is commonly misdiagnosed as type 2, which matters because the treatment approach differs. People with type 3c may need insulin earlier and often require enzyme supplements to help with digestion.
Drug-Induced and Secondary Diabetes
Certain medications can push blood sugar high enough to cause diabetes, particularly in people who already have some degree of insulin resistance. Corticosteroids are the most well-known culprits. All corticosteroids raise blood glucose, but some do so more aggressively than others. Dexamethasone and methylprednisolone are associated with larger blood sugar spikes compared to prednisolone or hydrocortisone. This matters for people on long-term steroid therapy for conditions like asthma, autoimmune diseases, or organ transplants.
Hormonal disorders can also trigger diabetes. Conditions that cause the body to overproduce cortisol or growth hormone raise blood sugar through the same insulin-resistance pathway as type 2. When the underlying condition is treated or the medication is stopped, blood sugar sometimes returns to normal, though not always. People who develop drug-induced diabetes often had borderline blood sugar to begin with, and the medication tipped them over the threshold.