Conditions guide

Type 2 Diabetes

Type 2 diabetes is a long-term condition in which the body does not use insulin well and blood sugar (glucose) levels stay higher than normal. It is the most common form of diabetes and develops gradually, often over many years.

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At a Glance

  • Type 2 diabetes accounts for the large majority of diabetes cases.
  • It involves insulin resistance and a gradual decline in the pancreas's ability to make enough insulin.
  • Many people have no symptoms early on, so screening blood tests are important.
  • Common tests include the hemoglobin A1C, fasting plasma glucose, and oral glucose tolerance test.
  • Over time, high blood sugar can damage blood vessels, nerves, eyes, kidneys, and the heart.
  • Management usually combines healthy eating, physical activity, monitoring, and often medicines.

What It Is

Insulin is a hormone made by the pancreas that helps glucose move from the blood into cells for energy. In type 2 diabetes, the body's cells respond poorly to insulin (insulin resistance), and over time the pancreas cannot keep up with the extra demand. As a result, glucose builds up in the blood.

Type 2 diabetes is different from type 1 diabetes, an autoimmune condition in which the body makes little or no insulin. Type 2 diabetes most often develops in adults, but it is increasingly seen in children and teens.

Prediabetes means blood sugar is higher than normal but not yet in the diabetes range. Many people with prediabetes can lower their risk of progressing to type 2 diabetes through lifestyle changes such as weight loss and increased activity.

Common Terminology

Insulin resistance
A state in which the body's cells do not respond well to insulin, so more insulin is needed to move glucose into cells.
Hemoglobin A1C
A blood test that reflects average blood sugar levels over roughly the past two to three months.
Prediabetes
Blood sugar levels above normal but below the threshold for diabetes.
Hyperglycemia
Higher than normal blood sugar.
Hypoglycemia
Lower than normal blood sugar, which can occur with some diabetes medicines and may cause shakiness, sweating, or confusion.
Neuropathy
Nerve damage, which in diabetes often affects the feet and legs first and can cause numbness, tingling, or pain.
Retinopathy
Damage to blood vessels in the retina of the eye that can affect vision.

Common Causes and Associations

Type 2 diabetes results from a mix of genetic and lifestyle factors.

  • Having overweight or obesity, especially extra fat around the abdomen, is a major risk factor.
  • Physical inactivity contributes to insulin resistance.
  • A family history of type 2 diabetes increases risk.
  • Risk rises with age, particularly after 35 to 45.
  • Some racial and ethnic groups, including African American, Hispanic/Latino, American Indian, Alaska Native, Asian American, and Pacific Islander people, have higher rates.
  • A history of gestational diabetes or polycystic ovary syndrome (PCOS) is associated with higher risk.
  • High blood pressure and abnormal cholesterol levels often occur alongside type 2 diabetes.

Symptoms and Features

This is a general description, not a diagnostic checklist. Symptoms often develop slowly, and many people have no noticeable symptoms for years.

  • Increased thirst and frequent urination.
  • Increased hunger and feeling very tired.
  • Blurred vision.
  • Slow-healing sores or frequent infections, such as skin, gum, or urinary infections.
  • Numbness or tingling in the hands or feet.
  • Unexplained weight loss, which is less common in type 2 than type 1 diabetes.
  • Patches of darker, velvety skin in body folds (acanthosis nigricans), which can be linked with insulin resistance.

Tests and Evaluation

Diagnosis is based on blood tests, usually confirmed with repeat testing unless symptoms and results are clear.

  • Hemoglobin A1C: a result of 6.5% or higher is generally used to diagnose diabetes, and 5.7% to 6.4% indicates prediabetes.
  • Fasting plasma glucose: 126 mg/dL or higher after not eating for at least 8 hours is generally consistent with diabetes.
  • Oral glucose tolerance test: a 2-hour reading of 200 mg/dL or higher after a sugary drink is generally consistent with diabetes.
  • A random plasma glucose of 200 mg/dL or higher with classic symptoms can also support a diagnosis.
  • Ongoing evaluation often includes kidney function tests, urine albumin, cholesterol, eye exams, and foot exams.
  • Labs may use slightly different methods, and results are interpreted by a clinician.

Treatment Overview

Treatment plans are individualized by a clinician and often change over time as the condition progresses.

  • Healthy eating patterns, often with guidance from a dietitian or diabetes educator, are a core part of management.
  • Regular physical activity helps the body use insulin more effectively.
  • Weight loss, when appropriate, can improve blood sugar levels and in some cases lead to remission.
  • Metformin is commonly used as an initial medicine, and other classes include SGLT2 inhibitors, GLP-1 receptor agonists, DPP-4 inhibitors, sulfonylureas, and insulin.
  • Blood sugar monitoring, using finger-stick meters or continuous glucose monitors, helps track control for some people.
  • Managing blood pressure and cholesterol, and not smoking, is important for reducing heart and blood vessel complications.
  • Regular eye, foot, kidney, and dental checks are part of routine diabetes care.

When Professional Care May Be Discussed

Very high blood sugar with extreme thirst, confusion, vomiting, or difficulty breathing, or low blood sugar with confusion, seizures, or loss of consciousness, is generally treated as a medical emergency; in the US, people are advised to call 911.

  • Screening for diabetes is generally recommended for adults with risk factors and for adults starting in middle age.
  • Symptoms such as increased thirst, frequent urination, and blurred vision are commonly evaluated by a healthcare professional.
  • Frequent low or high blood sugar readings are typically discussed with a clinician.
  • Foot sores, wounds that do not heal, or changes in skin color on the feet are generally evaluated promptly.
  • Changes in vision, swelling, or new numbness are usually reported to a clinician.
  • Illness, pregnancy, or planned surgery can affect diabetes management and are often discussed in advance.

Questions to Ask a Healthcare Professional

General questions people often find useful to bring to an appointment:

  • What do A1C and fasting glucose results mean, and how often are they usually checked?
  • What is the difference between prediabetes and type 2 diabetes?
  • Which complications are most important to screen for, and how often?
  • What role do diet and physical activity play in managing blood sugar?
  • How do different classes of diabetes medicines generally work?
  • What are the signs of low blood sugar, and how is it usually handled?
  • Is blood sugar monitoring at home generally recommended in this situation?

Sources

This guide was written in plain language from the following authoritative references.

  1. Diabetes Type 2 — MedlinePlus (U.S. National Library of Medicine)
  2. Type 2 Diabetes — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
  3. Type 2 diabetes — NHS

Last updated October 8, 2026. FreeDoc guides are general educational information and are not a substitute for care from a qualified professional.