Type 2 diabetes mellitus is a chronic condition where your body loses its ability to use insulin effectively, causing blood sugar levels to stay too high. It accounts for roughly 90% to 95% of all diabetes cases worldwide, and the number of adults living with diabetes has surpassed 800 million globally, more than quadrupling since 1990. Unlike type 1 diabetes, where the immune system destroys insulin-producing cells, type 2 develops because your cells gradually stop responding to insulin, a hormone that moves sugar from your blood into your cells for energy.
How Type 2 Differs From Type 1
The distinction matters because the two conditions have different causes, different progressions, and different treatment paths. Type 1 diabetes is an autoimmune disorder. The immune system attacks and destroys insulin-producing cells in the pancreas, leaving the body unable to make any insulin at all. It often appears in childhood, sometimes as young as 4 to 6 years old, and always requires insulin from the start.
Type 2 is a hormonal and metabolic condition. Your pancreas still produces insulin, at least initially, but your body doesn’t respond to it properly. This is called insulin resistance. Over time, the pancreas works harder and harder to compensate, and eventually it may produce less and less insulin or stop making it altogether. Type 2 is more common in adults but is becoming increasingly common in children and teens.
Symptoms That Develop Slowly
One of the most important things to know about type 2 diabetes is that symptoms often come on gradually. Many people live with it for years without knowing. When symptoms do appear, they typically include increased thirst, more frequent urination, persistent hunger, unexplained weight loss, and fatigue. These happen because your cells aren’t getting enough glucose for energy, and your kidneys are working overtime to filter excess sugar from your blood.
Other signs are easier to overlook: blurred vision, slow-healing cuts or sores, frequent infections, and numbness or tingling in your hands or feet. Some people develop patches of darkened skin, most often in the armpits and neck. Any combination of these warrants a blood test, especially if you have risk factors.
Who Is Most at Risk
Several factors increase your likelihood of developing type 2 diabetes, and most of them interact with each other. According to the CDC, you’re at higher risk if you:
- Have overweight or obesity
- Are 45 or older
- Have a parent or sibling with type 2 diabetes
- Are physically active fewer than three times a week
- Have non-alcoholic fatty liver disease
- Have had gestational diabetes or given birth to a baby weighing over 9 pounds
- Are African American, Hispanic or Latino, American Indian, Alaska Native, or certain Pacific Islander or Asian American populations
Having prediabetes is itself a major risk factor. Family history plays a significant role, suggesting a strong genetic component, but lifestyle factors like physical inactivity and excess weight are the primary drivers that push someone from genetic susceptibility into active disease.
How It Is Diagnosed
Diagnosis relies on blood tests that measure how much sugar is circulating in your blood. The two most common are the A1C test and the fasting blood glucose test. A1C reflects your average blood sugar over the past two to three months and is expressed as a percentage. A fasting glucose test measures your blood sugar after not eating for at least eight hours.
The thresholds break down clearly. A normal A1C is below 5.7%. Prediabetes falls between 5.7% and 6.4%, and the higher you are within that range, the greater your risk of progressing to diabetes. An A1C of 6.5% or above means diabetes. For fasting blood glucose, a reading of 126 mg/dL or higher indicates diabetes. Your doctor will typically confirm the result with a second test on a different day.
What Happens if It Goes Unmanaged
Chronically elevated blood sugar damages blood vessels throughout your body, and the complications fall into two broad categories. Small blood vessel damage affects your eyes, kidneys, and nerves. Large blood vessel damage raises your risk of heart attack, stroke, and peripheral artery disease.
Eye damage (retinopathy) can progress from mild changes to vision loss requiring laser treatment. Kidney damage (nephropathy) starts with small amounts of protein leaking into your urine and can eventually lead to kidney failure. Nerve damage (neuropathy) often begins as tingling or numbness in the feet and can progress to foot ulcers, infections, and in severe cases, amputation. Cardiovascular disease is the leading cause of death among people with type 2 diabetes. These complications develop over years, which is why early detection and consistent management matter so much.
Treatment and Management
Lifestyle changes form the foundation. Regular physical activity and modest weight loss (even 5% to 7% of body weight) can significantly improve insulin sensitivity and lower blood sugar. Diet changes that reduce refined carbohydrates and emphasize whole foods, fiber, and lean protein make a measurable difference.
When medication is needed, the approach depends on your overall health profile. For people without heart or kidney complications, metformin has traditionally been the first medication prescribed. It works by reducing the amount of sugar your liver releases and helping your cells respond better to insulin. For people who also have heart disease, heart failure, or chronic kidney disease, newer classes of medications may be started alongside or instead of metformin. These newer drugs, which help the body excrete excess sugar through urine or mimic a gut hormone that regulates blood sugar, have shown benefits beyond glucose control, including protecting the heart and kidneys.
Treatment is increasingly personalized. Your doctor considers your A1C level, your weight, your cardiovascular risk, and your kidney function when choosing medications. Some people need only one medication; others may eventually need combinations or insulin as the disease progresses.
Can Type 2 Diabetes Be Reversed?
Remission is possible, though not guaranteed. An international expert panel convened by the American Diabetes Association defined remission as achieving an A1C below 6.5% for at least three months without taking any diabetes medication. This can happen through significant weight loss, dietary changes, or bariatric surgery.
Remission is not the same as a cure. The underlying tendency toward insulin resistance remains, and blood sugar can rise again, especially if weight is regained or lifestyle changes aren’t sustained. People in remission still need regular A1C monitoring, typically at least once a year, because the condition can return without obvious symptoms. The earlier type 2 diabetes is caught and the less time the pancreas has been overworked, the better the chances of achieving remission.
The Global Scale of the Problem
Type 2 diabetes is no longer a disease of wealthy nations. Global diabetes prevalence in adults doubled from 7% to 14% between 1990 and 2022. The highest rates, around 20% of adults, are in South-East Asia and the Eastern Mediterranean. Perhaps more alarming, nearly 450 million adults with diabetes worldwide remain untreated. In Africa, South-East Asia, and the Eastern Mediterranean, fewer than 4 in 10 adults with diabetes are taking glucose-lowering medication. The World Health Organization has called for urgent action, noting a 3.5-fold increase in untreated cases since 1990.