Being diabetic means your body can’t properly manage blood sugar. In a healthy body, a hormone called insulin moves sugar from your bloodstream into your cells, where it’s used for energy. When you’re diabetic, that system is broken: either your body doesn’t make enough insulin, or your cells stop responding to it. The result is blood sugar that stays too high, and over time, that excess sugar damages organs throughout your body.
About 40.1 million people in the United States have diabetes, and more than 1 in 4 of them don’t know it.
How Blood Sugar Normally Works
Every time you eat, your digestive system breaks down carbohydrates into glucose, a simple sugar that enters your bloodstream. Your pancreas detects the rising blood sugar and releases insulin, which acts like a key that unlocks your cells so glucose can enter. Muscle cells, liver cells, and fat cells all depend on this process. When insulin is doing its job, blood sugar rises briefly after a meal and then drops back to a normal range.
In diabetes, this cycle breaks down. Glucose builds up in the blood instead of getting into cells. Your cells are essentially starving for energy while sugar accumulates in your bloodstream, and that combination drives most of the symptoms and long-term damage associated with the condition.
Type 1, Type 2, and Gestational Diabetes
There are several forms of diabetes, and they have different causes.
Type 1 Diabetes
Type 1 is an autoimmune disease. Your immune system mistakenly attacks the insulin-producing cells in your pancreas, eventually destroying them. Without those cells, your body makes little or no insulin. Type 1 is driven by a combination of genetic and environmental factors, and it often appears in childhood or adolescence, though it can develop at any age. People with type 1 diabetes need insulin every day to survive.
Type 2 Diabetes
Type 2 is far more common and develops differently. Your cells gradually become resistant to insulin, meaning they stop responding to it effectively. Your pancreas tries to compensate by producing more insulin, but eventually it can’t keep up. The combination of insulin resistance and declining insulin production causes blood sugar to rise. Type 2 is strongly linked to weight, physical inactivity, and genetics, and it typically develops in adults, though rising obesity rates have made it increasingly common in younger people.
Gestational Diabetes
Gestational diabetes is first diagnosed during pregnancy. Hormonal changes during pregnancy can make cells more resistant to insulin, and for some people, the pancreas can’t produce enough extra insulin to overcome that resistance. Blood sugar usually returns to normal after delivery, but having gestational diabetes raises your long-term risk of developing type 2.
Symptoms of High Blood Sugar
The classic symptoms of diabetes are frequent urination, excessive thirst, and increased hunger. These three are closely connected. When blood sugar gets too high, your kidneys work overtime to filter out the excess glucose, pulling extra water along with it. That leads to frequent urination, which dehydrates you and makes you intensely thirsty. Meanwhile, because glucose isn’t reaching your cells efficiently, your body signals that it needs more fuel, so you feel hungrier than usual.
Other common signs include unexplained weight loss (especially in type 1), blurred vision, fatigue, and slow-healing cuts or infections. Type 2 diabetes often develops so gradually that people have it for years without obvious symptoms, which is why so many cases go undiagnosed.
How Diabetes Is Diagnosed
Doctors use a few blood tests to diagnose diabetes. The most common is the A1C test, which measures your average blood sugar over the past two to three months. An A1C below 5.7% is normal. Between 5.7% and 6.4% is considered prediabetes. At 6.5% or higher, you’re diagnosed with diabetes.
A fasting blood sugar test works similarly. After not eating overnight, a blood sugar reading below 100 mg/dL is normal. Between 100 and 125 mg/dL falls in the prediabetes range. A reading of 126 mg/dL or higher indicates diabetes.
What Prediabetes Means
Prediabetes is exactly what it sounds like: blood sugar levels that are higher than normal but not yet high enough to qualify as diabetes. It’s a warning stage, and the good news is that it’s often reversible. A systematic review of interventions found that people who made lifestyle changes (typically improved diet and increased physical activity) were 18% more likely to return to normal blood sugar levels than those who didn’t. For every six people who adopted lifestyle modifications, one fully reversed their prediabetes within about a year and a half.
Certain medications can also help. Some drug classes showed even higher reversal rates in clinical studies, but lifestyle changes remain the first recommendation because they carry no side effects and improve overall health beyond just blood sugar.
Long-Term Health Risks
Persistently high blood sugar damages blood vessels throughout the body, and that damage shows up in specific organs over time.
Eyes. Diabetic eye disease is one of the most common complications. High blood sugar injures the tiny blood vessels in the retina, and the risk increases with both the severity of blood sugar elevation and the presence of high blood pressure. Retinal damage is also linked to higher rates of heart attack, stroke, and cardiovascular death.
Kidneys. Diabetes is a leading cause of kidney disease. Protein leaking into the urine (a sign of kidney damage) occurs in 15 to 40% of people with type 1 and 5 to 20% of people with type 2. Advanced kidney damage from diabetes increases the risk of stroke by more than four times.
Nerves. Nerve damage affects nearly half of all people with diabetes. It most often starts in the feet and hands, causing tingling, numbness, or pain. Because nerve damage reduces sensation, foot injuries can go unnoticed. More than 80% of diabetes-related amputations happen after a foot ulcer or undetected injury.
Heart and blood vessels. Diabetes significantly raises the risk of heart disease and stroke. The damage to small blood vessels in the eyes and kidneys is closely connected to damage in larger blood vessels supplying the heart and brain, meaning complications in one area often signal trouble elsewhere.
How Diabetes Is Managed
Managing diabetes centers on keeping blood sugar as close to a normal range as possible. The tools depend on the type.
People with type 1 diabetes rely on insulin, delivered either through injections or an insulin pump. Many also use a continuous glucose monitor (CGM), a small sensor placed just under the skin that tracks blood sugar levels throughout the day and night. CGMs can send alerts when levels get too high or too low, which makes it easier to catch problems early. Some systems pair a CGM with an insulin pump to create what’s called an artificial pancreas, which automatically adjusts insulin delivery based on real-time glucose readings. The first of these hybrid systems was approved in 2016, and several more have followed since.
For type 2 diabetes, management often starts with lifestyle changes: adjusting your diet to reduce refined carbohydrates and added sugars, increasing physical activity, and losing weight if needed. These changes alone can sometimes bring blood sugar into a healthy range. When lifestyle changes aren’t enough, medications that help your body use insulin more effectively or stimulate more insulin production are added. Some people with type 2 eventually need insulin as well, particularly as the condition progresses over many years.
Regardless of type, regular monitoring is essential. Checking blood sugar levels, whether through finger sticks or a CGM, helps you understand how food, activity, stress, and sleep affect your numbers. That feedback loop is what makes daily management possible.