Diabetes is a condition where your blood sugar stays too high because your body either can’t make enough insulin or can’t use it properly. Insulin is a hormone produced by your pancreas that acts like a key, unlocking your cells so they can absorb sugar from your blood and convert it into energy. When that system breaks down, sugar builds up in the bloodstream and damages your body over time. About 15.8% of U.S. adults have some form of diabetes, and roughly 4.5% of them don’t know it yet.
How Blood Sugar Regulation Works
Your pancreas contains clusters of cells called the islets of Langerhans, which house two key players: beta cells that produce insulin and alpha cells that produce glucagon. These two hormones work in a constant balancing act. When blood sugar rises after a meal, beta cells release insulin to help your cells absorb that sugar. When blood sugar drops too low, alpha cells release glucagon to signal your liver to release stored sugar back into the blood.
In diabetes, this balance breaks down. Either the beta cells are destroyed and can’t produce insulin at all, or your cells stop responding to insulin the way they should. In both cases, sugar accumulates in the bloodstream instead of entering your cells, leaving your cells starved for energy while your blood sugar climbs to damaging levels. Your body may also overproduce glucagon in response, pushing blood sugar even higher.
Type 1 Diabetes
Type 1 diabetes is an autoimmune condition. Your immune system mistakenly attacks and destroys the insulin-producing beta cells in your pancreas. Once those cells are gone, your body produces little to no insulin. This form affects roughly 1% of the population in developed countries and typically appears in childhood or adolescence, though it can develop at any age.
Because the body can no longer make its own insulin, people with type 1 diabetes need to take insulin every day for the rest of their lives. There’s no way to prevent it, and it isn’t caused by diet or lifestyle. The exact trigger is thought to involve a combination of genetic susceptibility and environmental factors, though researchers haven’t pinpointed the precise environmental causes.
Type 2 Diabetes
Type 2 is far more common, affecting about 8.5% of the global adult population. It develops when your cells become resistant to insulin, meaning the “key” no longer fits the lock as well as it should. Your pancreas tries to compensate by producing more insulin, but eventually it can’t keep up with the demand. The result is a slow, steady rise in blood sugar.
Insulin resistance is driven largely by excess body fat and aging. Fat tissue releases substances that interfere with how your cells process sugar and respond to insulin. This is why type 2 diabetes is strongly linked to being overweight, though it can also develop in people who aren’t. Unlike type 1, type 2 diabetes often responds to lifestyle changes, oral medications, or both. Some people with advanced type 2 diabetes eventually need insulin as well.
Gestational Diabetes
Gestational diabetes develops during pregnancy, typically around the 24th week. Pregnancy hormones and weight gain naturally increase insulin resistance in all women, but some women can’t produce enough extra insulin to overcome it. The condition usually has no noticeable symptoms, which is why screening between 24 and 28 weeks of pregnancy is standard.
The stakes are real: about half of women who develop gestational diabetes go on to develop type 2 diabetes later in life. Managing blood sugar during pregnancy, through diet, physical activity, and sometimes medication, helps protect both mother and baby from complications.
Less Common Types
Not every case fits neatly into the type 1 or type 2 categories. Latent autoimmune diabetes of adults (sometimes called type 1.5) is an autoimmune form that appears after age 30 and progresses much more slowly than typical type 1. People with this form don’t need insulin right away, often going six months or more before insulin becomes necessary. It’s frequently misdiagnosed as type 2 because it shows up in adults and starts off mild.
There’s also maturity-onset diabetes of the young (MODY), a rare genetic form caused by a single gene mutation. MODY runs strongly in families and can be distinguished from other types through genetic testing. It requires different treatment depending on which gene is involved.
Common Symptoms
The classic symptoms of diabetes stem directly from high blood sugar. When excess sugar spills into your urine, it pulls water along with it, leading to frequent urination and persistent thirst. Because your cells aren’t absorbing enough sugar for energy, you may feel unusually hungry and fatigued even after eating. Other warning signs include blurred vision, slow-healing sores, and frequent infections such as urinary tract infections or yeast infections.
Type 1 symptoms tend to appear suddenly and dramatically, sometimes over just a few weeks. Type 2 symptoms develop so gradually that many people live with the condition for years without realizing it. That slow onset explains why millions of Americans have undiagnosed diabetes.
How Diabetes Is Diagnosed
Doctors use a few standard blood tests, and any one of them can confirm a diagnosis. An A1C test measures your average blood sugar over the previous two to three months: 6.5% or higher indicates diabetes. A fasting blood sugar test (taken after not eating overnight) of 126 mg/dL or higher also qualifies. A third option, the oral glucose tolerance test, measures blood sugar two hours after drinking a sugary solution: 200 mg/dL or higher means diabetes.
Results between normal and diabetic ranges indicate prediabetes, a warning stage where blood sugar is elevated but not yet high enough for a diabetes diagnosis.
Prediabetes and Prevention
Prediabetes is more reversible than many people realize. A large meta-analysis of randomized trials found that lifestyle changes (primarily improved diet and regular exercise) reduced the risk of progressing to type 2 diabetes by 41% and increased the chances of returning to normal blood sugar levels by 44%. The benefits were strongest in people who had multiple markers of impaired blood sugar rather than just one borderline test result.
The lifestyle changes that make the biggest difference aren’t extreme. Moderate weight loss, even 5 to 7% of body weight, combined with about 150 minutes of physical activity per week, is consistently effective. For someone weighing 200 pounds, that’s losing 10 to 14 pounds.
Long-Term Complications
Persistently high blood sugar damages small blood vessels throughout your body. This is why diabetes can affect so many different organs, often simultaneously. The three most common complications involve the nerves, eyes, and kidneys, and they share overlapping mechanisms: chronic high blood sugar injures the lining of tiny blood vessels, triggers inflammation, and causes harmful compounds to accumulate in tissues.
Nerve damage (neuropathy) typically starts in the feet, causing numbness, tingling, or pain. Eye damage (retinopathy) can progress silently for years before causing vision loss. Kidney damage (nephropathy) gradually impairs your kidneys’ ability to filter waste from your blood. These three complications are closely interconnected. Research shows that the severity of one often predicts the presence and progression of the others, reinforcing that they all spring from the same underlying vascular damage.
Diabetes also significantly raises the risk of heart disease and stroke through damage to larger blood vessels. This is actually the leading cause of death in people with diabetes, which is why managing blood pressure and cholesterol matters alongside blood sugar control.
How Diabetes Is Managed
For type 1 diabetes, insulin is non-negotiable. People with type 1 take insulin through injections or an insulin pump, adjusting doses based on what they eat, their activity level, and their current blood sugar readings. Frequent blood sugar monitoring, either through finger sticks or a continuous glucose monitor worn on the skin, is part of daily life.
Type 2 diabetes management starts with lifestyle changes: meal planning, regular physical activity, and weight management. When those aren’t enough, medications come into play. The most commonly prescribed first-line medication helps the liver release less sugar into the bloodstream and makes cells more sensitive to insulin. Beyond that, several newer classes of drugs work in different ways: some help the kidneys flush out excess sugar through urine, others mimic gut hormones that stimulate insulin release and reduce appetite, and some slow down digestion of carbohydrates.
Regardless of type, managing diabetes is a daily commitment. It involves tracking what you eat, staying physically active, monitoring your blood sugar, and attending regular checkups to screen for complications in your eyes, kidneys, and feet. The goal is keeping blood sugar as close to normal as possible while minimizing episodes where it drops too low.