Diabetes mellitus, commonly referred to simply as diabetes, is a metabolic disease that causes high blood sugar.

The hormone insulin moves sugar from the blood into your cells to be stored or used for energy. With diabetes, your body either doesn’t make enough insulin or can’t effectively use the insulin it does make.

Untreated high blood sugar from diabetes can damage your nerves, eyes, kidneys, and other organs. But educating yourself about diabetes and taking steps to prevent or manage it can help you protect your health.

There are a few different types of diabetes:

  • Type 1: Type 1 diabetes is an autoimmune disease. The immune system attacks and destroys cells in the pancreas, where insulin is made. It’s unclear what causes this attack.
  • Type 2: Type 2 diabetes occurs when your body becomes resistant to insulin, and sugar builds up in your blood. It’s the most common type—about 90% to 95% of people living with diabetes have type 2.
  • Gestational: Gestational diabetes is high blood sugar during pregnancy. Insulin-blocking hormones produced by the placenta cause this type of diabetes.

A rare condition called diabetes insipidus is not related to diabetes mellitus, although it has a similar name. It’s a different condition in which your kidneys remove too much fluid from your body.

Each type of diabetes has unique symptoms, causes, and treatments.

Learn more about how these types differ from one another.

Prediabetes is the term that’s used when your blood sugar is higher than expected, but it’s not high enough for a diagnosis of type 2 diabetes. It occurs when the cells in your body don’t respond to insulin the way they should. This can lead to type 2 diabetes down the road.

Experts suggest that more than 1 in 3 Americans have prediabetes, but over 80% of people with prediabetes don’t even know it.

Diabetes symptoms are caused by rising blood sugar.

General symptoms

The general symptoms of diabetes include:

Symptoms in men

In addition to the general symptoms of diabetes, men with diabetes may have:

Symptoms in women

Women with diabetes can have symptoms such as:

Type 1 diabetes

Symptoms of type 1 diabetes can include:

  • extreme hunger
  • increased thirst
  • unintentional weight loss
  • frequent urination
  • blurry vision
  • tiredness

It may also result in mood changes.

Type 2 diabetes

Symptoms of type 2 diabetes can include:

  • increased hunger
  • increased thirst
  • increased urination
  • blurry vision
  • tiredness
  • sores that are slow to heal

It may also cause recurring infections. This is because high glucose levels make it harder for the body to heal.

Gestational diabetes

Most people who develop gestational diabetes don’t have any symptoms. Healthcare professionals often detect the condition during a routine blood sugar test or oral glucose tolerance test, which is usually performed between the 24th and 28th weeks of pregnancy.

In rare cases, a person with gestational diabetes will also experience increased thirst or urination.

The bottom line

Diabetes symptoms can be so mild that they’re hard to spot at first. Learn which signs should prompt a trip to the doctor.

Different causes are associated with each type of diabetes.

Type 1 diabetes

Doctors don’t know exactly what causes type 1 diabetes. For some reason, the immune system mistakenly attacks and destroys insulin-producing beta cells in the pancreas.

Genes may play a role in some people. It’s also possible that a virus sets off an immune system attack.

Type 2 diabetes

Type 2 diabetes stems from a combination of genetics and lifestyle factors. Having overweight or obesity increases your risk, too. Carrying extra weight, especially in your belly, makes your cells more resistant to the effects of insulin on your blood sugar.

This condition runs in families. Family members share genes that make them more likely to get type 2 diabetes and to be overweight.

Gestational diabetes

Gestational diabetes occurs as the result of hormonal changes during pregnancy. The placenta produces hormones that make a pregnant person’s cells less sensitive to the effects of insulin. This can cause high blood sugar during pregnancy.

People who are overweight when they get pregnant or who gain too much weight during pregnancy are more likely to get gestational diabetes.

The bottom line

Both genes and environmental factors play a role in triggering diabetes.

Certain factors increase your risk for diabetes.

Type 1 diabetes

You’re more likely to get type 1 diabetes if you’re a child or teenager, you have a parent or sibling with the condition, or you carry certain genes that are linked to the disease.

Type 2 diabetes

Your risk for type 2 diabetes increases if you:

Type 2 diabetes also disproportionately affects certain racial and ethnic populations.

Adults who have African American, Hispanic or Latino American, or Asian American ancestry are more likely to be diagnosed with type 2 diabetes than white adults, according to 2016 research. They’re also more likely to experience decreased quality of care and increased barriers to self-management.

Gestational diabetes

Your risk for gestational diabetes increases if you:

The bottom line

Your family history, environment, and preexisting medical conditions can all affect your odds of developing diabetes.

High blood sugar damages organs and tissues throughout your body. The higher your blood sugar is and the longer you live with it, the greater your risk for complications.

Complications associated with diabetes include:

Gestational diabetes

Unmanaged gestational diabetes can lead to problems that affect both the mother and baby. Complications affecting the baby can include:

A pregnant person with gestational diabetes can develop complications such as high blood pressure (preeclampsia) or type 2 diabetes. You may also require cesarean delivery, commonly referred to as a C-section.

The risk of gestational diabetes in future pregnancies also increases.

The bottom line

Diabetes can lead to serious medical complications, but you can manage the condition with medications and lifestyle changes.

Doctors treat diabetes with a few different medications. Some are taken by mouth, while others are available as injections.

Type 1 diabetes

Insulin is the main treatment for type 1 diabetes. It replaces the hormone your body isn’t able to produce.

Various types of insulin are commonly used by people with type 1 diabetes. They differ in how quickly they start to work and how long their effects last:

  • Rapid-acting insulin: starts to work within 15 minutes and its effects last for 2 to 4 hours
  • Short-acting insulin: starts to work within 30 minutes and lasts 3 to 6 hours
  • Intermediate-acting insulin: starts to work within 2 to 4 hours and lasts 12 to 18 hours
  • Long-acting insulin: starts to work 2 hours after injection and lasts up to 24 hours
  • Ultra-long acting insulin: starts to work 6 hours after injection and lasts 36 hours or more
  • Premixed insulin: starts working within 5 to 60 minutes and lasts 10 to 16 hours

Type 2 diabetes

Diet and exercise can help some people manage type 2 diabetes. If lifestyle changes aren’t enough to lower your blood sugar, you’ll need to take medication.

These drugs lower your blood sugar in a variety of ways:

DrugHow it worksExamples
alpha-glucosidase inhibitorsslow your body’s breakdown of sugars and starchy foodsacarbose (Precose) and miglitol
biguanidesreduce the amount of glucose your liver makesmetformin (Glucophage, Riomet)
DPP-4 inhibitorsimprove your blood sugar without making it drop too lowalogliptin (Nesina), linagliptin (Tradjenta), saxagliptin (Onglyza), and sitagliptin (Januvia)
glucagon-like peptidesstimulate your pancreas to produce more insulin; slow stomach emptyingsemaglutide (Ozempic), dulaglutide (Trulicity), exenatide (Byetta), and liraglutide (Victoza)
meglitinidesstimulate your pancreas to release more insulinnateglinide and repaglinide
SGLT2 inhibitorsrelease more glucose into the urinecanagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance)
sulfonylureasstimulate your pancreas to release more insulinglyburide (Glynase), glipizide (Glucotrol), and glimepiride (Amaryl)
thiazolidinedioneshelp insulin work betterpioglitazone (Actos) and rosiglitazone

You may need to take more than one of these medications. Some people with type 2 diabetes also take insulin.

Gestational diabetes

If you receive a diagnosis of gestational diabetes, you’ll need to monitor your blood sugar level several times per day during pregnancy. If it’s high, dietary changes and exercise may be enough to bring it down.

Research has found that about 15% to 30% of women who develop gestational diabetes will need insulin to lower their blood sugar. Insulin is safe for the developing baby.

The bottom line

The treatment regimen your doctor recommends will depend on the type of diabetes you have and its cause.

Healthy eating is a central part of managing diabetes. In some cases, changing your diet may be enough to manage the disease.

Type 1 diabetes

Your blood sugar level rises or falls based on the types of foods you eat. Starchy or sugary foods make blood sugar levels rise rapidly. Protein and fat cause more gradual increases.

Your medical team may recommend that you limit the amount of carbohydrates you eat each day. You’ll also need to balance your carb intake with your insulin doses.

Check out this guide to starting a type 1 diabetes diet.

Type 2 diabetes

Eating the right types of foods can both manage your blood sugar and help you lose any excess weight.

Carb counting is an important part of eating for type 2 diabetes. A dietitian can help you figure out how many grams of carbohydrates to eat at each meal.

In order to keep your blood sugar levels steady, try to eat small meals throughout the day. Emphasize healthy foods such as:

Certain other foods can hurt efforts to manage your blood sugar.

Gestational diabetes

Eating a well-balanced diet is important for both you and your baby during these 9 months. Making the right food choices can also help you avoid diabetes medications.

Watch your portion sizes, and limit sugary or salty foods. Although you need some sugar to feed your growing baby, you should avoid eating too much. Check out other do’s and don’ts for healthy eating with gestational diabetes.

The bottom line

Work with a registered dietitian, if you have access to one. They can help you design an individualized diabetes meal plan. Getting the right balance of protein, fat, and carbs can help you manage your blood sugar.

Along with diet and treatment, exercise plays an essential role in diabetes management. This is true for all types of diabetes.

Staying active helps your cells react to insulin more effectively and lower your blood sugar levels. Exercising regularly can also help you:

If you have type 1 or type 2 diabetes, general guidance is to aim for at least 150 minutes of moderate-intensity exercise each week. There are currently no separate exercise guidelines for people who have gestational diabetes. But if you’re pregnant, start out slowly and gradually increase your activity level over time to avoid overdoing it.

Diabetes-friendly exercises include:

  • walking
  • swimming
  • dancing
  • cycling

Talk with your doctor about safe ways to incorporate activity into your diabetes management plan. You may need to follow special precautions, like checking your blood sugar before and after working out and making sure to stay hydrated.

Consider working with a personal trainer or exercise physiologist who has experience working with people who have diabetes. They can help you develop a personalized workout plan tailored to your needs.

Anyone who has symptoms of diabetes or is at risk for the condition should be tested. People are routinely tested for gestational diabetes during their second trimester or third trimester of pregnancy.

Doctors use these blood tests to diagnose prediabetes and diabetes:

  • The fasting plasma glucose (FPG) test measures your blood sugar after you’ve fasted for 8 hours.
  • The A1C test provides a snapshot of your blood sugar levels over the previous 3 months.

How to diagnose gestational diabetes

To diagnose gestational diabetes, your doctor will test your blood sugar levels between the 24th week and 28th week of pregnancy. There are two types of tests:

  • Glucose challenge test: During a glucose challenge test, your blood sugar is checked an hour after you drink a sugary liquid. If your results are standard, no more testing is done. If blood sugar levels are high, you’ll need to undergo a glucose tolerance test.
  • Glucose tolerance test: During a glucose tolerance test, your blood sugar is checked after you fast overnight. Then you’re given a sugary drink and your blood sugar is re-tested after 1 hour and again after 2 hours. Gestational diabetes is diagnosed if any of these three readings come back noting high blood sugar.

The earlier you are diagnosed with diabetes, the sooner you can start treatment. Find out whether you should get tested, and get more information on tests your doctor might perform.

If you don’t already have a primary care specialist, you can browse doctors in your area through the Healthline FindCare tool.

Type 1 diabetes is not preventable because it’s caused by an issue with the immune system. Some causes of type 2 diabetes, such as your genes or age, aren’t under your control either.

Yet many other diabetes risk factors are manageable. Most diabetes prevention strategies involve making simple adjustments to your diet and fitness routine.

If you’ve received a diagnosis of prediabetes, here are a few things you can do to delay or prevent type 2 diabetes:

These aren’t the only ways to prevent diabetes. Discover more strategies that may help you avoid this chronic health condition.

People who’ve never had diabetes can suddenly develop gestational diabetes in pregnancy. Hormones produced by the placenta can make your body more resistant to the effects of insulin.

Pre-gestational diabetes

Some people had diabetes before they conceived carry it with them into pregnancy. This is called pre-gestational diabetes.

Risks to your newborn

Diabetes during pregnancy can lead to complications for your newborn, such as jaundice or breathing problems.

If you’re diagnosed with pre-gestational or gestational diabetes, you’ll need special monitoring to prevent complications.

Does gestational diabetes disappear on its own?

Gestational diabetes should go away after you deliver, but it does significantly increase your risk of getting diabetes later. About half of people with gestational diabetes will go on to develop type 2 diabetes.

Children can get both type 1 and type 2 diabetes. Managing blood sugar is especially important in young people because diabetes can damage important organs such as the heart and kidneys.

Type 1 diabetes

The autoimmune form of diabetes often starts in childhood. One of the main symptoms is increased urination. Kids with type 1 diabetes may start wetting the bed after they’ve been toilet trained.

Extreme thirst, fatigue, and hunger are also signs of the condition. It’s important that children with type 1 diabetes get treatment right away. The condition can cause high blood sugar and dehydration, which can be medical emergencies.

Type 2 diabetes

Type 1 diabetes used to be called juvenile diabetes because type 2 was so rare in children. Now that more children have overweight or obesity, type 2 diabetes is becoming more common in this age group.

Some children living with type 2 diabetes don’t experience symptoms. Others may experience:

  • increased thirst
  • frequent urination
  • extreme fatigue
  • blurry vision

Type 2 diabetes is often diagnosed based on medical history, a physical exam, and bloodwork.

Untreated type 2 diabetes can cause lifelong complications, including heart disease, kidney disease, and blindness. Healthy eating and exercise can help your child manage their blood sugar and prevent these problems.

Type 2 diabetes is more prevalent than ever in young people. Learn how to spot the signs so you can report them to your child’s doctor.

Some types of diabetes — like type 1 — are caused by factors that are out of your control. Others — like type 2 — can be prevented by making better food choices, increasing activity, and losing weight.

Discuss potential diabetes risks with your doctor. If you’re at risk, have your blood sugar tested and follow your doctor’s advice for managing your blood sugar.