What Is Diabetes? Types, Symptoms, Causes & Treatment

Written by Jaclyn Weiner, RD, RDN, MEd, MS

Last updated September 21, 2026

Diabetes is one of the most common chronic health conditions in the United States. It’s also widely misunderstood. Many people know it involves “blood sugar,” but fewer understand what that actually means for the body, or how different the three main types really are.

Diabetes is more than simply having high blood sugar. Understanding what causes blood glucose to rise, which type of diabetes you may have, and how it’s diagnosed can help you take the right next steps. This guide covers all of that in plain language, without assuming you already know the medical terms. For a quick clinical overview alongside this guide, MedlinePlus is a useful reference point.

Not everyone with diabetes has obvious symptoms. That’s part of what makes understanding this condition, and knowing when to get tested, genuinely important. Diabetes is also one of the most common health issues people face, which is part of why accurate, accessible information about it matters so much.

Quick answer

• Diabetes is a chronic condition where blood glucose (blood sugar) stays too high, because the body doesn’t make enough insulin, doesn’t use it effectively, or both.
• There are three main types: type 1, type 2, and gestational diabetes. Each has different causes.
• Common symptoms include frequent urination, increased thirst, fatigue, and blurred vision, but some people have no noticeable symptoms at all.
• Diabetes is diagnosed through blood tests, not symptoms alone or home glucose meters.
• Type 2 diabetes can often be prevented or delayed. Type 1 currently cannot be prevented.
• Left unmanaged, diabetes can contribute to serious complications over time, but ongoing care and monitoring help most people manage it well.

What is diabetes?

To understand diabetes, it helps to understand two things first: glucose and insulin.

What glucose and insulin do

Glucose is a type of sugar that comes mainly from the food you eat. It travels through your bloodstream and serves as your body’s main source of energy.

Insulin is a hormone made by the pancreas. According to the CDC, insulin acts like a key, helping glucose move out of the bloodstream and into your cells, where it can actually be used for energy.

What goes wrong in diabetes

Diabetes develops when this system breaks down in one of two ways. Either the body doesn’t produce enough insulin, or the body’s cells stop responding to insulin properly. Either way, glucose builds up in the bloodstream instead of reaching the cells that need it.

Over time, persistently high blood glucose can affect blood vessels, nerves, and organs throughout the body. This is part of why ongoing management matters, not just occasional symptom relief.

What are the different types of diabetes?

There are three main types of diabetes, and they have genuinely different causes, even though they share the same basic problem: elevated blood glucose.

Type 1 diabetes

Type 1 diabetes is an autoimmune condition. The body’s immune system mistakenly attacks and destroys the beta cells in the pancreas that produce insulin. As a result, the body makes little or no insulin at all.

Type 1 diabetes can develop at any age, though it’s most often diagnosed in children, teens, and young adults. Symptoms often appear relatively quickly. Diet and lifestyle habits do not cause type 1 diabetes, and people with this type require insulin treatment to survive.

Type 2 diabetes

Type 2 diabetes is the most common form, accounting for roughly 90% to 95% of diagnosed cases in U.S. adults. It occurs when the body doesn’t use insulin properly, a state called insulin resistance, and over time may not produce enough insulin to keep up with demand.

Symptoms of type 2 diabetes can develop gradually, or they may be absent entirely for years. Several risk factors contribute to type 2 diabetes, and lifestyle changes and medications often form part of its management.

Gestational diabetes

Gestational diabetes develops during pregnancy, typically in the second or third trimester. According to the CDC, it usually doesn’t cause noticeable symptoms, which is why routine testing during weeks 24 to 28 of pregnancy is standard care.

Gestational diabetes can affect the health of both the pregnant person and the baby if left unmanaged. It generally resolves after delivery, though it raises the risk of developing type 2 diabetes later in life.

Other, less common forms

A small number of diabetes cases result from other causes. Monogenic diabetes results from a single gene mutation, and some cases develop as a result of another disease or as a side effect of certain medications. These forms are far less common than type 1, type 2, and gestational diabetes.

What are the symptoms of diabetes?

Diabetes symptoms vary depending on the type and how quickly it develops. Importantly, some people have no symptoms at all, especially in the early stages.

Common symptoms across diabetes types

Several symptoms are shared across most types of diabetes, according to NIDDK:

• Frequent urination
• Increased thirst
• Increased hunger, even after eating
• Fatigue
• Unexplained weight loss
• Blurred vision
• Slow-healing sores
• Frequent infections
• Numbness or tingling in the hands or feet

If you’ve been feeling persistently tired without an obvious cause, it’s worth knowing that fatigue can have many explanations beyond diabetes. Our guide to what causes fatigue covers the broader picture.

Type 1 diabetes symptoms

Type 1 diabetes symptoms tend to appear quickly and can become severe. Left untreated, type 1 diabetes can lead to diabetic ketoacidosis (DKA), a serious complication. Warning symptoms of DKA include:

• Nausea or vomiting
• Abdominal pain
• Trouble breathing
• Fruity-smelling breath
• Severe dehydration or fainting

DKA is a medical emergency. Trouble breathing alongside these other symptoms deserves immediate attention; our guide to shortness of breath covers this symptom in more general contexts as well.

Type 2 diabetes symptoms

Type 2 diabetes symptoms often develop slowly, sometimes over several years. Many people have no obvious symptoms at all. Diabetes is frequently discovered during routine blood testing, or after complications, like vision changes or chest pain, have already developed. Our guide to chest pain covers when this particular symptom needs urgent evaluation.

Some people notice episodes of dizziness related to blood sugar swings, particularly if they’re already being treated for diabetes. Our guide to what causes dizziness covers the range of possible causes.

When should you see a doctor?

Persistent symptoms or known risk factors are reasons to get tested, not to self-diagnose. According to NIDDK, anyone with possible diabetes symptoms should be tested, and home glucose meters alone cannot diagnose diabetes. Only a proper blood test, ordered and interpreted by a healthcare professional, can confirm a diagnosis.

What causes diabetes?

Diabetes doesn’t have one universal cause. Each type develops differently.

Causes of type 1 diabetes

Type 1 diabetes results from an autoimmune response that destroys insulin-producing cells in the pancreas. Genetic susceptibility plays a role, and researchers believe environmental factors may help trigger the immune response in people who are already genetically predisposed. Diet and lifestyle do not cause type 1 diabetes.

Causes of type 2 diabetes

Type 2 diabetes generally develops from a combination of insulin resistance and, over time, inadequate insulin production. Genetic factors play a real role, and several contributing factors raise risk, including excess body weight and physical inactivity. It’s rarely caused by just one factor alone.

Causes of gestational diabetes

During pregnancy, hormonal changes can make the body less sensitive to insulin. For most pregnant people, the pancreas produces enough extra insulin to compensate. When it can’t keep up with the increased demand, gestational diabetes develops.

What are the risk factors for diabetes?

Having a risk factor doesn’t mean you’ll definitely develop diabetes. It means your likelihood is higher than someone without that factor.

Type 1 risk factors

• Family history of type 1 diabetes
• Genetic susceptibility
• Certain age patterns, most commonly childhood through young adulthood
• Possible environmental triggers, still an active area of research

Type 2 risk factors

• Family history of type 2 diabetes
• Prediabetes
• Overweight or obesity
• Physical inactivity
• Increasing age
• Previous gestational diabetes
• Certain other health conditions

Gestational diabetes risk factors

• Overweight or obesity before pregnancy
• Family history of type 2 diabetes
• Previous gestational diabetes
• Certain other pregnancy-related factors

Regular physical activity is one of the more consistently supported ways to lower type 2 diabetes risk. Our guide to the benefits of exercise covers what the evidence actually shows.

How is diabetes diagnosed?

Diabetes and prediabetes are diagnosed using blood tests interpreted by a healthcare professional, not through symptoms alone.

A1C test

The A1C test measures your average blood glucose over roughly the past three months. It generally doesn’t require fasting beforehand, which makes it convenient for both screening and diagnosis.

Fasting plasma glucose test

This test measures blood glucose after a period of fasting, usually at least eight hours without food.

Oral glucose tolerance test

This test measures how your body responds to glucose over time. You drink a glucose solution, and your blood glucose is measured at intervals afterward. It’s commonly used to screen for gestational diabetes.

Random plasma glucose test

This test can be done at any time, regardless of when you last ate. It’s particularly useful when someone already has clear diabetes symptoms.

Current diagnostic thresholds

According to the American Diabetes Association’s Standards of Care, current diagnostic criteria for diabetes in non-pregnant adults are:

In most cases, a diagnosis requires two abnormal results, either from two different tests or the same test repeated on a different day. These thresholds can be updated as clinical guidance evolves, so always confirm current numbers with a healthcare provider rather than relying solely on any single source, including this one.

How is diabetes treated?

Treatment depends heavily on the type of diabetes, individual health needs, current blood glucose levels, and other medical factors. There’s no single approach that fits everyone.

Type 1 diabetes treatment

People with type 1 diabetes need insulin to survive. Treatment typically includes:

• Insulin, delivered by injection or pump
• Regular blood glucose monitoring
• Coordinated nutrition planning
• Physical activity
• Diabetes technology, like continuous glucose monitors, where appropriate

Type 2 diabetes treatment

Type 2 diabetes management often combines several approaches:

• Nutrition and lifestyle changes
• Physical activity
• Weight management, when appropriate for the individual
• Oral medications
• Injectable medications
• Insulin, when needed
• Regular blood glucose monitoring
• Managing related factors like blood pressure and cholesterol

Gestational diabetes treatment

Management usually includes blood glucose monitoring, nutrition guidance, and physical activity when medically appropriate. Medication is added when lifestyle measures alone aren’t enough to keep blood glucose in a healthy range. Regular prenatal monitoring continues throughout the pregnancy.

Nutrition’s role across all types

Nutrition plays a meaningful supporting role in diabetes management, particularly for type 2 and gestational diabetes. Our guides to what makes a balanced diet and what counts as a healthy diet cover the fundamentals, while our nutrition facts resource offers a broader reference.

Specific dietary patterns come up often in diabetes discussions. The Mediterranean diet and eating patterns built around anti-inflammatory foods have research support for supporting metabolic health. High-fiber foods and adequate intake from high-protein foods can also help support steadier blood glucose levels. Some people explore intermittent fasting as part of their approach, though this should be discussed with a doctor first if you have diabetes, since timing changes can affect blood glucose and medication needs.

Some research has also looked at ginger’s effect on blood glucose specifically. Our guide to ginger’s overall health effects covers where that evidence stands, alongside its other studied uses.

Can diabetes be prevented?

Whether diabetes can be prevented depends entirely on which type you’re talking about.

Type 1 diabetes

There is currently no established way to prevent type 1 diabetes. Because it results from an autoimmune process, it isn’t related to diet, weight, or activity level.

Type 2 diabetes

Type 2 diabetes can sometimes be prevented or delayed through several well-supported measures:

• Increased physical activity
• Healthy eating patterns
• Weight management, when appropriate
• Addressing prediabetes early, before it progresses

If you’re working on weight as part of a diabetes-prevention plan, our roundup of 2026 weight loss trends covers current, evidence-based approaches worth knowing about.

Gestational diabetes

Not all cases of gestational diabetes can be prevented. Appropriate prenatal care and managing known risk factors ahead of and during pregnancy may help reduce risk for some people.

What happens if diabetes isn’t managed?

Persistently high blood glucose can affect multiple organ systems over time. This isn’t meant to cause alarm. It’s meant to explain why ongoing management genuinely matters.

Potential long-term complications

Poorly controlled or persistent high blood glucose can contribute to:

• Heart disease
• Stroke
• Kidney disease
• Nerve damage (neuropathy)
• Eye disease and vision problems
• Foot problems
• Dental problems
• Sexual and bladder problems

These complications tend to develop gradually, often over years. This is exactly why regular monitoring and consistent management matter, even when you’re feeling fine day to day.

Diabetes vs. prediabetes: what’s the difference?

These two terms are related but distinct, and understanding the difference matters for what happens next.

The key distinction

Prediabetes means your blood glucose is higher than the healthy range but not high enough to meet the diagnostic threshold for diabetes. Diabetes means your blood glucose has reached the diagnostic range established by healthcare professionals and reflected in the table above.

Prediabetes is a meaningful warning sign, not a diagnosis to ignore. Many of the same lifestyle changes that help prevent type 2 diabetes can help reverse prediabetes for some people.

Building healthy habits alongside diabetes care

Diabetes management works best as part of a broader, sustainable approach to health, not as an isolated set of rules.

Lifestyle factors that support blood glucose management

A few everyday habits genuinely support better blood glucose control alongside medical treatment. Our guides to how to reduce stress and how to improve sleep cover two factors that measurably affect blood glucose regulation, not just general wellbeing.

For a broader framework, our overview of how to improve your health, our healthy living tips resource, and our guide to how to live a healthy lifestyle all touch on how nutrition, activity, sleep, and stress work together. Building general healthy habits is a reasonable foundation whether you’re managing diabetes, prediabetes, or simply trying to lower your risk.

Frequently asked questions

What is diabetes in simple terms?

Diabetes is a condition where your blood sugar stays too high because your body doesn’t make enough insulin, doesn’t use insulin properly, or both. Insulin is the hormone that normally helps move sugar from your blood into your cells for energy.

What are the first signs of diabetes?

Early signs often include increased thirst, frequent urination, unusual fatigue, and increased hunger. That said, many people, especially those with type 2 diabetes, have no noticeable early symptoms at all.

What are the 3 main types of diabetes?

The three main types are type 1 diabetes, an autoimmune condition; type 2 diabetes, the most common form, involving insulin resistance; and gestational diabetes, which develops during pregnancy.

Can diabetes go away?

Type 1 diabetes doesn’t go away and requires lifelong insulin treatment. Gestational diabetes usually resolves after delivery. Type 2 diabetes can sometimes go into remission, meaning blood glucose returns to a non-diabetic range, through significant lifestyle changes or weight loss, but this differs from a cure. Ongoing monitoring generally remains important even during remission.

Can you have diabetes without symptoms?

Yes. Many people, particularly those with type 2 diabetes, have few or no noticeable symptoms, sometimes for years. This is exactly why routine screening matters for people with risk factors, rather than waiting for symptoms to appear.

How is diabetes diagnosed?

Diabetes is diagnosed through blood tests performed and interpreted by a healthcare professional, using established criteria like the A1C test, fasting plasma glucose test, oral glucose tolerance test, or random plasma glucose test.

Is diabetes caused by eating too much sugar?

Not directly, and the answer differs by type. Type 1 diabetes is an autoimmune condition unrelated to diet. Type 2 diabetes has multiple contributing factors, including genetics, weight, and activity level; diet plays a role within that broader picture, but “eating too much sugar” alone is an oversimplification of a more complex condition.

Can people with diabetes live a normal life?

Yes, for most people. With appropriate management, monitoring, and regular healthcare follow-up, many people with diabetes lead full, active lives. Consistent care and communication with a healthcare team make a real difference in long-term outcomes.

When to seek medical care

Concerned you may have diabetes? If you’re experiencing symptoms or have risk factors for diabetes, speak with a qualified healthcare professional about whether you should be tested. Early diagnosis and consistent management meaningfully reduce the risk of long-term complications.

Sources

1. Centers for Disease Control and Prevention (CDC). About Diabetes
2. CDC. Diabetes Risk Factors
3. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Symptoms & Causes of Diabetes
4. NIDDK. What Is Diabetes?
5. American Diabetes Association. Standards of Care in Diabetes, Classification and Diagnosis
6. MedlinePlus, National Library of Medicine. Diabetes

Medical disclaimer

This article is for general information and education. It is not medical advice and cannot diagnose diabetes or any other condition. If you have symptoms of diabetes or risk factors for the condition, talk to a qualified healthcare provider about testing.

Read our full Medical Disclaimer.