Type 2 diabetes is a chronic condition where your body stops using insulin effectively, causing blood sugar to build up in the bloodstream instead of entering cells for energy. It accounts for roughly 90% to 95% of all diabetes cases, and as of 2024, about 589 million adults worldwide are living with some form of diabetes, representing over 11% of the global adult population. Unlike type 1 diabetes, where the immune system destroys the cells that make insulin, type 2 develops gradually and is closely tied to weight, activity level, and genetics.
How It Develops in the Body
Insulin is a hormone your pancreas releases to help cells absorb sugar (glucose) from your blood. In type 2 diabetes, two things go wrong. First, your cells become resistant to insulin’s signal, so they don’t absorb glucose the way they should. Second, your pancreas struggles to produce enough extra insulin to compensate.
Obesity is the most common driver of insulin resistance. Excess body fat, particularly around the abdomen, triggers low-grade inflammation across multiple tissues including fat, muscle, liver, and even the brain. That inflammation interferes with insulin’s ability to do its job at the cellular level. Specifically, it disrupts the chemical chain reaction insulin normally kicks off when it docks onto a cell’s surface. Over time, your pancreas works harder and harder to keep up. Eventually, its insulin-producing cells wear out, and blood sugar levels rise to the point where damage begins.
Mitochondria, the energy-producing structures inside your cells, also play a role. Because glucose and fat metabolism both depend on mitochondria, any dysfunction in these structures can worsen insulin resistance and its downstream effects.
Who Is Most at Risk
Type 2 diabetes most commonly begins in middle age or later, and more than 20% of Americans over 65 currently have the disease. But age alone doesn’t explain it. Several factors stack on top of each other:
- Excess weight. Most people develop some degree of insulin resistance as they age, but carrying extra weight, especially with limited physical activity, amplifies that resistance dramatically.
- Family history. There’s no single inheritance pattern, but having a parent or sibling with type 2 diabetes raises your risk. The more affected family members you have, the higher the likelihood.
- Ethnicity. In the United States, the disease is most common among Native Americans and Alaska Natives, followed by people of African American and Hispanic descent. Non-Hispanic white and Asian Americans have somewhat lower rates.
These risk factors interact. A person with a family history who also carries excess weight and is physically inactive faces a much steeper risk than someone with just one of those factors.
Symptoms to Recognize
Type 2 diabetes often develops slowly, and many people have it for years before noticing anything unusual. When symptoms do appear, they reflect what happens when too much sugar stays in the bloodstream:
- Frequent urination and increased thirst. Your kidneys work overtime to filter excess glucose, pulling more water with it.
- Increased hunger. Because glucose isn’t reaching your cells efficiently, your body signals that it needs more fuel.
- Unexplained weight loss. Without adequate glucose absorption, the body starts burning fat and muscle for energy.
- Fatigue and irritability. Cells deprived of their primary energy source leave you drained.
- Blurry vision. High blood sugar pulls fluid from the lenses of your eyes, temporarily affecting focus.
Some symptoms are more specific to type 2 than type 1: slow-healing cuts and sores, dark patches of skin around the neck, armpits, or groin (a condition called acanthosis nigricans), and numbness or tingling in the hands and feet. Frequent urinary tract infections and yeast infections are also common, since elevated sugar creates an environment where bacteria and fungi thrive.
How It’s Diagnosed
Diagnosis relies on blood tests that measure how much glucose is circulating. The most commonly used tests, with thresholds set by the American Diabetes Association, are:
- A1C test. This reflects your average blood sugar over the past two to three months. An A1C of 5.7% to 6.4% indicates prediabetes. An A1C of 6.5% or higher means diabetes.
- Fasting blood glucose. After an overnight fast, a reading of 100 to 125 mg/dL falls in the prediabetes range. A reading of 126 mg/dL or higher indicates diabetes.
Prediabetes is worth paying attention to. It means blood sugar is elevated but not yet high enough for a diabetes diagnosis, and it’s the stage where lifestyle changes can have the biggest impact on preventing or delaying progression.
Long-Term Complications
Persistently high blood sugar damages blood vessels throughout the body. The complications fall into two broad categories based on which vessels are affected.
Damage to small blood vessels (microvascular complications) leads to problems in three main areas. In the eyes, it causes diabetic retinopathy, where tiny blood vessels in the retina leak or grow abnormally, potentially leading to vision loss. In the kidneys, it leads to diabetic nephropathy, a progressive decline in kidney function that can eventually require dialysis. In the nerves, it causes neuropathy, most commonly felt as numbness, tingling, or pain in the feet and hands. Severe neuropathy combined with poor circulation can lead to foot ulcers that heal poorly and, in the worst cases, may require amputation.
Damage to large blood vessels (macrovascular complications) raises the risk of heart disease, stroke, and peripheral arterial disease. These cardiovascular complications are the leading cause of death among people with type 2 diabetes. Research shows that small-vessel and large-vessel damage are strongly interrelated: the same processes that harm tiny capillaries in the eyes or kidneys also contribute to heart disease.
How It’s Managed
Management starts with lifestyle changes, and for many people, those changes remain the foundation even after medication is added. Regular physical activity improves insulin sensitivity directly, as does losing even a modest amount of weight. Dietary adjustments that reduce blood sugar spikes, particularly cutting back on refined carbohydrates and sugary drinks, make a measurable difference.
When lifestyle changes aren’t enough to reach target blood sugar levels, medication enters the picture. The most widely prescribed first-line drug works by reducing the amount of glucose your liver releases into the bloodstream while also helping your muscles absorb glucose more effectively. It has been used for decades and remains a cornerstone of treatment partly because of its safety profile and low cost.
Newer classes of medications have expanded the options significantly. One class works by mimicking a gut hormone that stimulates insulin release after meals, slows digestion, and reduces appetite, often leading to substantial weight loss alongside blood sugar control. Another class works at the kidneys, causing excess glucose to be filtered out through urine rather than reabsorbed back into the bloodstream. Both of these newer drug classes have also shown benefits for heart and kidney health beyond just lowering blood sugar, which has changed how doctors think about treatment priorities.
Can Type 2 Diabetes Be Reversed?
Remission is possible. An international expert consensus defines it as achieving an A1C below 6.5% that lasts at least three months without any diabetes medication. This can happen through significant weight loss, dietary interventions, or bariatric surgery. When A1C testing isn’t reliable for a particular individual, a fasting blood glucose below 126 mg/dL can serve as an alternative marker.
Remission is more likely when pursued earlier in the disease, before the insulin-producing cells in the pancreas have sustained too much damage. It does not mean the disease is cured. The underlying tendency toward insulin resistance remains, and blood sugar levels need ongoing monitoring because relapse is common, particularly if weight is regained. Still, for people who achieve it, remission means a period of living free from both the medication burden and the elevated blood sugar that drives complications.