Type 2 diabetes is a condition where your body stops responding properly to insulin, the hormone that moves sugar from your blood into your cells for energy. It accounts for roughly 90% of all diabetes cases worldwide, and global prevalence in adults has doubled from 7% to 14% between 1990 and 2022, with more than 800 million adults now living with diabetes.
How Type 2 Diabetes Develops
Every cell in your body needs glucose for fuel, and insulin acts as the key that unlocks the door to let glucose in. In type 2 diabetes, that key stops working well. Your muscle cells, fat cells, and liver cells gradually lose their sensitivity to insulin, so glucose builds up in the bloodstream instead of entering cells where it’s needed.
In muscle tissue, insulin normally triggers a transporter protein to move to the cell surface and pull glucose inside. When muscles become resistant to insulin, that transporter stays locked away inside the cell. Fat tissue develops a similar problem: it stops responding to insulin’s signal to absorb glucose and, worse, starts releasing fatty acids into the blood, which further raises blood sugar. The liver, meanwhile, keeps producing glucose even when blood sugar is already high, because insulin’s “stop” signal no longer gets through.
Your pancreas tries to compensate by pumping out more insulin. For a while, this brute-force approach keeps blood sugar in check. But the insulin-producing beta cells in the pancreas eventually wear out. Once both insulin resistance and beta cell burnout are present, blood sugar rises sharply and type 2 diabetes progresses.
Who Is at Risk
The CDC identifies several major risk factors for type 2 diabetes:
- Weight: Having overweight or obesity is the single strongest modifiable risk factor.
- Age: Risk increases at 45 and continues rising with each decade.
- Family history: A parent or sibling with type 2 diabetes significantly raises your likelihood.
- Physical inactivity: Exercising fewer than three times a week increases risk.
- Ethnicity: African American, Hispanic/Latino, American Indian, Alaska Native, some Pacific Islander, and some Asian American populations face higher rates.
- Gestational diabetes: Having had diabetes during pregnancy, or delivering a baby weighing over 9 pounds, is a risk factor that persists for years afterward.
- Non-alcoholic fatty liver disease: Fat accumulation in the liver is both a contributor to and a marker of insulin resistance.
Genetics load the gun, but lifestyle pulls the trigger. Most people who develop type 2 diabetes carry a combination of inherited susceptibility and environmental factors like excess weight and sedentary habits.
Symptoms to Recognize
Type 2 diabetes often develops so gradually that people live with it for years before noticing anything wrong. When blood sugar climbs high enough to cause symptoms, the most common early signs are frequent urination, increased thirst, blurred vision, and unusual fatigue. You urinate more because your kidneys are working overtime to flush excess glucose, which in turn dehydrates you and drives the thirst.
If blood sugar stays high for a long time without treatment, more serious symptoms can develop: fruity-smelling breath, dry mouth, abdominal pain, nausea, shortness of breath, and confusion. These can signal a dangerous buildup of toxic acids in the blood called ketoacidosis, which requires emergency care.
How It Is Diagnosed
Three blood tests can confirm a diagnosis. An A1C test measures your average blood sugar over the past two to three months; diabetes is diagnosed at 6.5% or higher. A fasting blood glucose test (taken after at least eight hours without eating) diagnoses diabetes at 126 mg/dL or above. An oral glucose tolerance test, which measures blood sugar two hours after drinking a sugary solution, diagnoses diabetes at 200 mg/dL or above. Your doctor typically repeats an abnormal result on a separate day to confirm the diagnosis.
Long-Term Complications
Persistently high blood sugar damages blood vessels and nerves throughout the body. The complications fall into two broad categories: damage to small blood vessels (eyes, kidneys, nerves) and damage to large blood vessels (heart, brain, legs).
Nerve damage, called neuropathy, is one of the most common complications. It typically starts as tingling or numbness at the tips of the toes or fingers and slowly spreads upward. Over time it can progress to burning pain or complete loss of sensation, which makes foot injuries easy to miss and slow to heal.
Diabetes raises the risk of serious eye conditions including cataracts, glaucoma, and damage to the blood vessels of the retina (diabetic retinopathy), which can lead to blindness if left untreated. It also increases the risk of heart disease, stroke, high blood pressure, and narrowed arteries. Heart disease is the leading cause of death among people with type 2 diabetes.
Treatment and Daily Management
Current guidelines recommend starting most people on a combination of metformin and an SGLT2 inhibitor (a class of drug that helps the kidneys remove excess glucose through urine). If someone cannot tolerate metformin, an SGLT2 inhibitor alone is typically used. For people who also have heart disease, injectable medications that mimic a gut hormone called GLP-1 (the same class that includes semaglutide, marketed as Ozempic) are added to the regimen. People diagnosed before age 40 may also be considered for these newer drugs early on.
Medication is only part of the picture. Dietary changes play a central role. Reducing overall carbohydrate intake has proven effective for blood sugar control and weight loss. Most guidelines recommend a moderate carbohydrate intake focused on nutrient-dense, whole foods rather than an extreme restriction. Interestingly, the usefulness of the glycemic index (a ranking of how quickly foods raise blood sugar) is now uncertain, as recent research has challenged its previously claimed benefits.
Regular physical activity improves insulin sensitivity directly by helping muscles absorb glucose without needing as much insulin. Even moderate exercise three or more times a week makes a measurable difference.
Can Type 2 Diabetes Be Reversed?
Remission is possible, and weight loss is the most important factor. Remission is defined as blood sugar returning to a non-diabetic range and staying there for at least six months without any diabetes medications. A landmark trial called DiRECT found high rates of remission among people who lost more than 22 pounds (about 10 kg) and sustained that loss over one to two years.
Remission is more likely the earlier it’s pursued after diagnosis, before beta cells in the pancreas have suffered too much damage. It does not mean the disease is cured permanently. Without ongoing weight management, blood sugar levels tend to creep back up over time, so sustained lifestyle changes remain essential even after reaching remission.