Types of Diabetes Mellitus

Medically Reviewed by Zilpah Sheikh, MD on June 18, 2024
Written by Frances Gatta, Rebecca Buffum Taylor
9 min read

Diabetes mellitus, also called diabetes, is a term for several conditions involving how your body turns food into energy. The term comes from the Greek word “diabetes,” which means to siphon or to pass through, and the Latin word “mellitus,” which means sweet. In 2021, 529 million people worldwide and 38.4 million in the U.S. had diabetes. 

When you eat a carbohydrate, your body turns it into a sugar called glucose and sends that to your bloodstream. Your pancreas releases insulin, a hormone that helps move glucose from your blood into your cells, which use it for energy.

When you have diabetes and don’t get treatment, your body doesn’t use insulin like it should. Too much glucose stays in your blood, a condition usually called high blood sugar. This can cause health problems that may be serious or even life-threatening.

There’s no cure for diabetes. But with treatment and lifestyle changes, you can live a long, healthy life.

Diabetes comes in different forms, depending on the cause.

Prediabetes is when your blood sugar is higher than it should be but not high enough for your doctor to diagnose it as diabetes. Normal blood sugar levels are between 70 mg/dL and 99 mg/dL. Blood sugar levels in people with prediabetes are between 110 mg/dL and 125 mg/dL.

Prediabetes often has no symptoms. More than a third of people in the U.S. have it, but about 90% don't know. If you have prediabetes, you might notice darkened skin on areas like your neck, armpits, and groin.

Rarely, you may have other symptoms like:

  • Unexplained weight loss or gain
  • Wanting to eat more
  • Weakness
  • Fatigue
  • Sweating
  • Blurred vision
  • Cuts or bruises that heal slowly
  • Having skin infections or gum bleeding often

Over 70% of people with prediabetes later develop type 2 diabetes. You’re also likely to start having heart, kidney, and nerve damage. 

You can lower these risks and potentially reverse prediabetes by: 

  • Exercising regularly
  • Eating a healthy diet
  • Maintaining a healthy weight
  • Managing your stress levels
  • Quitting smoking 

Your doctor might recommend medications like acarbose and metformin if you can’t follow these lifestyle changes or you’re at a very high risk of having type 2 diabetes. 

Type 1 diabetes is also called insulin-dependent diabetes. It used to be called juvenile-onset diabetes because it was thought to start more often in childhood. However, more research has shown it happens as frequently in children and adults. 

Type 1 diabetes is an organ-specific autoimmune condition. It happens when your body attacks your pancreas with antibodies. The organ is damaged and doesn't make insulin. It affects 2 million people, including about 304,000 children and teens in the U.S.

Your genes might cause this type of diabetes. It could also happen because of problems with cells in your pancreas that make insulin. Type 1 diabetes cannot be prevented. 

Type 1 diabetes symptoms happen quickly, in a few days to weeks. They include:

  • Feeling thirst and hunger often
  • Peeing more
  • Blurry vision
  • Fatigue
  • Unexplained weight loss

About 30% of people with type 1 diabetes have a life-threatening condition that causes loss of consciousness, called diabetic coma, as their first symptom. 

Get medical help immediately if you or your child show any of these symptoms:

  • Breath that smells fruity
  • Dry or flushed skin
  • Nausea
  • Difficulty breathing
  • Being unable to focus
  • Confusion
  • Vomiting
  • Stomach pain

Many of the health problems that can come with type 1 happen because of damage to tiny blood vessels in your eyes (diabetic retinopathy), nerves (diabetic neuropathy), and kidneys (diabetic nephropathy). People with type 1 also have a higher risk of heart disease and stroke.

A doctor may use a test called random plasma glucose (RPG) to check how much sugar you have in your blood when diagnosing type 1 diabetes. They may also use an A1c blood test to estimate your blood sugar levels over the last 3 months. Your doctor uses it to see how well your blood sugar is controlled. That helps them know your risk of complications.

Treatment for type 1 diabetes involves injecting insulin into the fatty tissue just under your skin. You might use:

  • Syringes
  • Insulin pens that use prefilled cartridges and a thin needle
  • Jet injectors that use high-pressure air to send a spray of insulin through your skin
  • Pumps that send insulin through a tube to a catheter under the skin of your belly

If you have type 1 diabetes, you’ll need to make changes, including:

  • Frequent testing of your blood sugar levels
  • Careful meal planning
  • Daily exercise
  • Taking insulin and other medications, including pramlintide or metformin, as needed

Type 2 diabetes used to be called non-insulin-dependent or adult-onset diabetes. But it’s become more common in children and teens over the past 20 years, largely because more young people are overweight or obese. About 90% of people with diabetes have type 2.

When you have type 2 diabetes, your pancreas usually creates some insulin. But either it’s not enough or your body doesn’t use it like it should. Insulin resistance, when your cells don’t respond to insulin, usually happens in fat, liver, and muscle cells.

Type 2 diabetes is often milder than type 1. But it can still cause major health complications, especially in the tiny blood vessels in your kidneys, nerves, and eyes. Type 2 also raises your risk of heart disease and stroke.

People who have obesity -- more than 20% over their target body weight for their height -- have an especially high risk of type 2 diabetes and the health problems that can follow. Obesity often causes insulin resistance, so your pancreas has to work harder to make more insulin. But it’s still not enough to keep your blood sugar levels where they should be.

Treatment for type 2 diabetes involves keeping a healthy weight, eating right, and exercising. Some people need medication, too.

Your doctor might do an A1c test a few times a year to see how well you’ve been controlling your blood sugar.

Pregnancy usually causes some form of insulin resistance. If this becomes diabetes, it’s called gestational. Doctors often spot it in 2%-10% of pregnancies. You may be diagnosed in the middle or late pregnancy with a: 

  • Glucose challenge test, which checks how your body responds to sugar
  • Or an oral glucose tolerance test, which checks how well your body uses and stores sugar

It usually causes no or mild symptoms like feeling thirstier or peeing more often. It goes away after giving birth. But people who have had gestational diabetes are 8-10 times more likely to develop type 2 diabetes and have twice the risk of developing heart disease compared to those who have not had it.  

If you’ve had gestational diabetes, you’ll need to be tested for type 2 diabetes every 3 years for the rest of your life.

Gestational diabetes is more of a risk for the baby than the mother. Because your blood sugars travel through their placenta to the baby, it’s important to control gestational diabetes to protect the baby's growth and development. 

A baby might have unusual weight gain before birth, trouble breathing at birth, or a higher risk of obesity and diabetes later in life. You might need a cesarean section because of an overly large baby, or they might have damage to their heart, kidney, nerves, and eyes.

Gestational diabetes treatment involves:

  • Careful meal planning to make sure you get enough nutrients without too much fat and calories
  • Daily exercise
  • Keeping weight gain under control
  • Taking insulin to control your blood sugar levels, if needed

Rarely, diabetes can happen due to changes in a single gene that can affect how much insulin the body can produce. When this is the case, it is called monogenic diabetes. 

The gene mutation is often passed down from one or both parents. However, gene mutations may also happen unexpectedly. 

In the U.S., monogenic diabetes happens in 1% to 4% of all diabetes cases. 

The two main types of monogenic diabetes are

  • Neonatal diabetes mellitus, which happens in babies
  • Maturity-onset diabetes of the young, which occurs in teens and young adults

Many times, doctors mistake monogenic diabetes for type 2 diabetes. But a doctor might suspect monogenic diabetes if: 

  • Diabetes is diagnosed before a baby is 6 months old
  • A child or young adult has diabetes, including those having a family history of diabetes, that shows neither type 1 nor type 2 diabetes features.
  • A person has slightly high blood sugar levels after not eating for some time. 

Then, they recommend genetic testing to confirm it and determine which specific type you have. They might also test your family members to see if they have it.

You may get diabetes medicines you take by mouth or insulin injections to treat it.

Secondary diabetes is a type of diabetes that happens because of another primary condition, which may include:

  • Endocrine dysfunctions or hormone-related problems like having too much cortisol hormone (Cushing's syndrome) and having too much growth hormone (acromegaly)
  • Disorders involving the pancreas
  • Having excess iron
  • Cystic fibrosis (CF)
  • Polycystic ovarian syndrome (PCOS)

Medications like steroids may also trigger secondary diabetes. 

Treatment may involve managing the underlying cause, making lifestyle changes, and taking insulin and other medications to control your blood sugar levels.

Type 1 and type 2 diabetes are the most common types of diabetes. Type 1 diabetes affects 1.3 million people in the U.S., and type 2 diabetes occurs in 37 million people. 

Type 1 diabetes happens when the immune system mistakenly attacks your pancreas, causing it to stop producing insulin. Both genetic and environmental factors play a role in causing this immune response. 

Type 2 diabetes is a hormonal condition that happens when your body doesn't respond well to insulin, which leads to high blood sugar levels. With time, the pancreas in people with type 2 diabetes may stop working as well as it should until it stops being able to produce insulin.

Type 1 diabetes symptoms usually happen suddenly within a few days to a week. Type 2 diabetes symptoms take a while, about a year, to develop.

People with type 1 diabetes need insulin medicine because the body can’t make it anymore. People with type 2 diabetes only need insulin when their pancreas stops making it. 

Diabetes is a group of conditions that affect how well your body turns food into energy. It causes high blood sugar levels that can lead to serious health issues like heart disease, eye damage, dementia, stroke, and kidney damage. Your doctor will manage it depending on the type you have. You may need insulin injections and antidiabetic medicines. They’ll also recommend following lifestyle changes like eating a healthy diet and exercising.  

Is type 2 diabetes manageable?

Yes, type 2 diabetes is manageable with medicines and healthy lifestyle changes.

What causes diabetes mellitus?

What causes diabetes will depend on the type. It may be related to your genes, lifestyle, and family history. But all forms of diabetes cause you to have high blood sugar levels.

What are diabetes mellitus types 1 and 2?

Types 1 and 2 diabetes are the most common type of diabetes. Type 1 diabetes happens when your immune system attacks and damages your pancreas, causing it to stop making enough insulin. Type 2 diabetes occurs when your body stops using insulin well.