What Is Maturity-Onset Diabetes of the Young?

Written by Sharon Liao
Medically Reviewed by Michael Dansinger, MD on August 28, 2025
7 min read

Maturity-onset diabetes of the young (MODY) refers to a group of rare kinds of diabetes. They run in families and usually show up when you're an adolescent or young adult. It's sometimes called monogenic diabetes or MODY syndrome. Like type 1 and type 2 diabetes, MODY diabetes affects the way your body uses and stores sugar from food. But treatment can be different, so it's important to get the right diagnosis.

MODY is caused by a mutation, or change, in one of your genes. This is different from type 1 and type 2 diabetes, which are caused by a combination of different genes and other things, such as obesity.

"Type 1 diabetes is an autoimmune disease, and type 2 diabetes is typically thought of as something that occurs after many years of overuse of the pancreas," says Beth Gottesman, MD, an endocrinologist at Phoenix Children's in Arizona. "The insulin is eventually unable to keep up with the amount of sugar and carbohydrate that is being consumed. However, MODY diabetes is something that's within a person from birth because it's genetic."

The genetic change that happens because of MODY diabetes keeps your pancreas from making enough insulin, a hormone that helps control the level of sugar in your blood.

Who gets it?

MODY diabetes is usually inherited, so your odds of getting it are higher if you have family members with the disease. It's a monogenic condition, which means that if you have a parent with MODY, there's a 50% chance that you'll have it too. In many cases, the disease reaches across multiple generations, affecting a grandparent, parent, and child.

The disease usually affects teens and young adults under 35. But you can get it at any age. Unlike type 2 diabetes, MODY isn't linked to obesity or high blood pressure. People with MODY are often at a healthy weight.

How common is MODY?

MODY is a rare type of diabetes that doctors sometimes confuse with type 1 or type 2 diabetes. The condition makes up less than 5% of all diabetes cases. Since it can be misdiagnosed, more people may have it than doctors realize.

As Gottesman explains, "It takes a sleuth to put together the pieces and think, 'This isn't really fitting either the type 1 or the type 2 picture, so I need to expand my mind and think of other options,' because there are treatment implications for MODY diabetes that may be easier than using insulin."

The signs of MODY can depend on which of your genes is affected. In some cases, there may be no symptoms at all. But in general, the disease comes on gradually. You may have high blood sugar for years before you notice one of these warning signs:

MODY 1 (HNF4A mutation)

HNF4A (MODY 1) is a less common type of MODY. You may need a genetic test to tell it apart from MODY 3 (HNF1A mutation). People with MODY 1 may have low "good" cholesterol (HDL) and may be more like those with type 2 diabetes. 

People with MODY 1 are often born bigger than usual and sometimes have low blood sugar as babies. If someone in the family had low blood sugar as a baby and later got diabetes, doctors might check for this type.

MODY 2 (GCK mutation)

GCK (MODY 2) is a type of MODY caused by a problem in a gene that helps your body know when to release insulin. Because of this, people with this type usually have slightly higher blood sugar, even when they haven't eaten. It's usually mild, doesn't worsen over time, and doesn't cause symptoms. Most people with GCK-MODY have a low risk of serious problems.

MODY 3 (HNF1A mutation)

The HNF1A gene causes a majority of MODY cases — around 70%. With this type of MODY, diabetes happens when your pancreas makes less insulin than normal. It usually happens in adolescence or your early twenties.

MODY 4 (PDX1 mutation)

MODY 4 happens when a change in the PDX1 gene stops your pancreas from growing normally and making insulin, which leads to diabetes.

MODY 5 (HNF1B mutation)

HNF1B (MODY 5) is a rare form of MODY that makes up less than 5% of MODY cases. Many people with this gene mutation get diabetes at a young age. It also causes kidney cysts, gout, and changes to the uterus.

MODY 6 (NEUROD1 mutation)

NEUROD1 MODY happens due to a change in the gene that controls how your pancreas develops. This type can appear starting in puberty, all the way to your 60s.

Other types of MODY

Scientists have detected at least 14 different MODY mutations. Other types include changes to the following genes: INS, PAX 4, ABCC8, KCNJ11, KLF11, CEL, BLK, and APPL1. These gene changes can affect at what age you get diabetes, how you respond to treatment, and whether the condition affects other parts of your body besides your pancreas.

You should get genetic testing for MODY if:

  • Doctors diagnosed you with diabetes when you were 6 months old or younger.
  • Your fasting blood sugar levels are regularly higher than normal.
  • You test negative for antibodies linked to diabetes, which suggests a cause of diabetes unrelated to autoimmune disease (as seen in type 1 diabetes).
  • You have a family member diagnosed with diabetes at a young age (under 30 years).
  • Your body continues to make C-peptide, a substance the pancreas releases into your body when making insulin. People with type 1 diabetes usually stop making their own insulin a few months or years after diagnosis.

Gottesman explains that when she meets a patient who has just received a diabetes diagnosis, she asks whether the condition runs in their family. "If I hear a pretty extensive family history, especially on one side of the family, that makes me think that perhaps this is more genetic and less likely to be type 1 or type 2 diabetes, which are somewhat inheritable but not as significantly so as MODY."

Like other types of diabetes, MODY causes high blood sugar levels. If you don't get treatment, over time it can lead to complications such as:

  • Nerve damage
  • Heart disease
  • Eye damage, including blindness
  • Foot problems
  • Skin problems such as infections
  • Blood vessel problems
  • Kidney problems
  • Problems with your reproductive organs
  • Low magnesium
  • Gout
  • Overactive parathyroid glands
  • Liver problems
  • Brain development issues
  • Autism
  • Small size at birth

Because there can be no symptoms or mild ones, you and your doctor may not realize at first that you have MODY. Your doctor may diagnose you with diabetes when a blood test shows that your blood sugar levels are high. The next step is to figure out what kind of diabetes you have.

Your doctor will ask about your family history of diabetes. They may order blood tests that can rule out other types of the disease besides MODY.

Based on these results, your doctor might suggest that you get genetic testing to confirm you have MODY. They'll take a sample of DNA from your saliva or blood and send it to a lab. A technician will look for changes in a gene that cause MODY.

MODY 1 and 3 treatment

With these types, diet changes can help manage your blood sugar in the beginning. But over time, your insulin-producing cells may get weaker, and you may need medication. You'll likely take a drug called a sulfonylurea or a GLP-1 receptor agonist.

MODY 2 treatment

This disease is usually managed through diet and exercise. You usually don't have to take medicine.

MODY 4 treatment

Oral diabetes medicines can help treat this type of MODY. Research shows metformin and DPP-4 inhibitors work well.

MODY 5 treatment

You'll need to take insulin to treat it. This rare form of MODY can harm other organs, such as your kidneys. You'll need treatment for complications, such as kidney cysts or kidney failure.

MODY 6 treatment

This type tends to appear later in life, around age 40. You'll take insulin to treat it.

Maturity-onset diabetes of the young (MODY) is an uncommon type of diabetes that usually affects teens and young adults. It also runs in families, so if one or both of your parents have it, there's a 50% higher chance that you'll also have it. Doctors suggest genetic testing for MODY if you were young when diagnosed or if someone in your family has it. Treatment for MODY ranges from diet and exercise to medication to manage your blood sugar.

Is MODY diabetes reversible?

There's no cure for MODY, but you can manage the condition and predict it through genetic testing.

What is the difference between diabetes and MODY?

MODY is a type of diabetes that runs in families. It usually happens in younger people, but you can get a diagnosis at any age.

How rare is MODY diabetes?

MODY is an uncommon form of diabetes, making up less than 5% of all diabetes cases. But this number may actually be higher since doctors tend to mistake it for type 1 or type 2 diabetes.

Is MODY diabetes dangerous?

Like other forms of diabetes, MODY can be dangerous due to high blood sugar if left undiagnosed or untreated. It can also cause other health problems that affect your eyes, kidneys, nerves, and blood vessels.

Is MODY diabetes autoimmune?

No. Unlike type 1 diabetes, MODY diabetes is a genetic condition, not an autoimmune disease.