Type 2 diabetes (type 2 DM, or type 2 diabetes mellitus) is a chronic condition where your body struggles to use insulin properly, causing blood sugar levels to stay too high. It accounts for more than 95% of all diabetes cases worldwide, and the number of people living with diabetes has quadrupled from 200 million in 1990 to 830 million in 2022.
How Type 2 Diabetes Develops
Insulin is a hormone your pancreas makes to help blood sugar (glucose) move from your bloodstream into your cells, where it’s used for energy. In type 2 diabetes, two things go wrong. First, your cells in your muscles, fat, and liver stop responding well to insulin, a problem called insulin resistance. Second, your pancreas can’t produce enough insulin to compensate. The result is that glucose builds up in your blood instead of reaching your cells.
This is different from type 1 diabetes, where the immune system destroys the insulin-producing cells in the pancreas entirely. In type 2, the pancreas still makes insulin, but the system breaks down gradually over months or years.
Common Symptoms
Type 2 diabetes often develops slowly, and many people have it for years without knowing. When symptoms do appear, the most common ones are:
- Frequent urination: Your kidneys work harder to filter the excess glucose, pulling more water along with it.
- Increased thirst: Losing extra fluid through urination leaves you dehydrated.
- Persistent hunger: Because glucose can’t get into your cells efficiently, your body signals that it needs more fuel, even right after eating.
Other signs include blurred vision, slow-healing cuts, numbness or tingling in the hands and feet, fatigue, and unexplained weight loss. Some people only discover the condition through a routine blood test.
Who Is at Risk
Several factors raise your chances of developing type 2 diabetes. Being overweight is the most significant. Most adults with a BMI of 25 or higher face increased risk, though the threshold is lower for Asian Americans (BMI of 23 or higher) and higher for Pacific Islanders (BMI of 26 or higher). Where you carry weight matters too: men with a waist circumference over 40 inches and women with a waist over 35 inches are at higher risk.
Other major risk factors include:
- Being 35 or older
- Having a family history of diabetes
- Being physically inactive
- Having prediabetes (blood sugar levels that are elevated but not yet in the diabetic range)
- A history of gestational diabetes or giving birth to a baby weighing 9 pounds or more
Certain racial and ethnic groups, including African American, American Indian, Asian American, Hispanic/Latino, and Pacific Islander populations, also face higher risk.
How It Is Diagnosed
Doctors use one of three blood tests to diagnose type 2 diabetes. An A1C test measures your average blood sugar over the past two to three months; a result of 6.5% or higher indicates diabetes. A fasting blood glucose test (taken after not eating for at least 8 hours) diagnoses diabetes at 126 mg/dL or higher. A two-hour oral glucose tolerance test, where you drink a sugary solution and have blood drawn two hours later, diagnoses diabetes at 200 mg/dL or higher.
If your numbers fall between the normal range and the diabetes threshold, you may be diagnosed with prediabetes. As of 2022, 14% of adults worldwide were living with diabetes, up from 7% in 1990.
Long-Term Complications
When blood sugar stays elevated over years, it damages blood vessels throughout the body. The complications fall into two broad categories based on the size of blood vessels affected.
Small blood vessel damage can lead to kidney disease (which in severe cases requires dialysis or transplant), vision problems including damage to the blood vessels in the retina, and nerve damage that typically starts as numbness or pain in the feet and hands. Large blood vessel damage raises the risk of heart attack, stroke, heart failure, and peripheral vascular disease, which reduces blood flow to the legs and, in serious cases, can lead to amputation.
These complications are not inevitable. Keeping blood sugar, blood pressure, and cholesterol well managed significantly lowers the risk of all of them.
Lifestyle Management
Lifestyle changes form the foundation of type 2 diabetes management, whether or not medication is also needed. The goal is at least 150 minutes of moderate-intensity physical activity per week, which could be brisk walking, cycling, swimming, or anything that gets your heart rate up. Spreading this across five days is easier on your body than cramming it into two.
Losing even a modest amount of weight can improve insulin sensitivity meaningfully. The focus with food is on managing carbohydrate intake, since carbohydrates have the biggest impact on blood sugar. This doesn’t mean eliminating carbs entirely but rather choosing higher-fiber, slower-digesting sources and eating consistent portions. Working with a dietitian to build a realistic, sustainable eating pattern tends to be more effective than following restrictive diets.
Medications for Type 2 Diabetes
Metformin is typically the first medication prescribed. It works by reducing the amount of glucose your liver releases into your bloodstream and by helping your muscle cells respond to insulin more effectively. It’s taken as a pill, usually twice a day.
If metformin alone isn’t enough, your doctor may add a second medication from another class. The most notable newer options include GLP-1 receptor agonists (most are injected weekly) and SGLT2 inhibitors (taken as a daily pill). GLP-1 receptor agonists are particularly notable because they can lower blood sugar significantly while also promoting weight loss, and some have been shown to reduce heart disease risk. SGLT2 inhibitors work by causing your kidneys to remove excess glucose through urine, and they also offer heart and kidney protection.
Other classes include DPP-4 inhibitors, which extend the life of natural hormones that lower blood sugar, and sulfonylureas, which stimulate the pancreas to produce more insulin. Some people with type 2 diabetes eventually need insulin injections, especially as the condition progresses over many years.
Prevention and Remission
For people with prediabetes, a structured lifestyle change program can reduce the risk of developing type 2 diabetes by 58%, and by 71% for those over age 60. These programs typically focus on gradual weight loss through better eating and regular physical activity.
For people already diagnosed, remission is possible. An international expert consensus defines remission as an A1C below 6.5% sustained for at least three months after stopping all diabetes medication. This is most achievable early in the disease, often through significant weight loss. Remission doesn’t mean the condition is cured permanently; it means blood sugar has returned to normal levels, and ongoing monitoring is still important because the underlying tendency toward insulin resistance remains.