Diabetes is a condition where your blood sugar stays too high because your body either can’t make 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 bloodstream and use it for energy. When that system breaks down, sugar builds up in your blood and, over time, damages organs throughout your body. About 40 million people in the United States have diabetes, roughly 12% of the population, and another 115 million American adults have prediabetes, a warning stage where blood sugar is elevated but not yet in the diabetic range.
How Insulin Works and What Goes Wrong
After you eat, your digestive system breaks food down into glucose, a simple sugar that enters your bloodstream. Your pancreas detects the rising blood sugar and releases insulin. Insulin signals your muscle, fat, and liver cells to open up and pull glucose inside, where it’s either burned for energy or stored for later use. This process keeps your blood sugar within a tight, healthy range.
In diabetes, this cycle fails. In some people, the pancreas stops producing insulin entirely. In others, the cells gradually stop responding to insulin’s signal, a problem called insulin resistance. Either way, glucose stays trapped in the bloodstream instead of reaching the cells that need it. The result is chronically high blood sugar, which silently damages blood vessels, nerves, and organs over months and years.
Types of Diabetes
Type 1
Type 1 diabetes is an autoimmune condition. Your immune system mistakenly attacks and destroys the insulin-producing cells in your pancreas, leaving your body unable to make insulin at all. It often appears in childhood, sometimes as young as four to six years old, though it can develop at any age. People with Type 1 diabetes need insulin every day for the rest of their lives because there is no way to restart the destroyed cells.
Type 2
Type 2 diabetes is far more common and develops differently. Your pancreas still makes insulin, at least initially, but your muscle, liver, and fat cells stop responding to it effectively. Your pancreas tries to compensate by producing more and more insulin, but eventually it can’t keep up. Over time, it may slow its insulin production significantly or stop making it altogether. Type 2 is more common in adults, though it’s increasingly diagnosed in children and teens. Excess weight, inactivity, and genetics all play a role.
Gestational Diabetes
Some people develop diabetes during pregnancy. Hormonal shifts make it harder for the body to use insulin efficiently, and blood sugar rises. Extra weight before pregnancy increases the risk, though experts still don’t fully understand why some pregnant people develop it and others don’t. Gestational diabetes usually resolves after delivery, but it raises the long-term risk of developing Type 2 diabetes later in life. It can also lead to complications like a larger-than-normal baby, difficult delivery, and a higher chance of needing a C-section.
Common Symptoms
High blood sugar often builds gradually, and many people, particularly those with Type 2, have no obvious symptoms at first. In fact, roughly 11 million American adults have diabetes without knowing it. When symptoms do appear, the earliest and most recognizable ones are:
- Frequent urination: your kidneys work overtime to flush excess sugar out through urine
- Increased thirst: all that extra urination leaves you dehydrated
- Unusual fatigue: your cells aren’t getting the fuel they need
- Blurred vision: high blood sugar pulls fluid from the lenses of your eyes
If blood sugar climbs much higher and stays there, more serious warning signs develop. These include fruity-smelling breath, nausea, abdominal pain, confusion, and in severe cases, loss of consciousness. This dangerous state happens when the body starts breaking down fat for energy instead of glucose, producing toxic acids called ketones. It’s a medical emergency most common in Type 1 diabetes but possible in Type 2 as well.
How Diabetes Is Diagnosed
Doctors use a few simple blood tests, and any one of them can confirm a diagnosis. The most common are:
- A1C test: measures your average blood sugar over the past two to three months. Normal is below 5.7%, prediabetes falls between 5.7% and 6.4%, and 6.5% or higher means diabetes.
- Fasting blood sugar: taken after an overnight fast. Normal is below 100 mg/dL, prediabetes is 100 to 125 mg/dL, and 126 mg/dL or higher indicates diabetes.
- Oral glucose tolerance test: you drink a sugary solution and your blood sugar is measured two hours later. Below 140 mg/dL is normal, 140 to 199 is prediabetes, and 200 or above is diabetes.
These thresholds matter because prediabetes is a critical window. Your blood sugar is elevated enough to cause some harm, but lifestyle changes at this stage can dramatically lower your risk of progressing to full diabetes.
Long-Term Damage to the Body
Chronically high blood sugar acts like sandpaper on the inside of your blood vessels, and the damage accumulates over years. The smallest blood vessels are hit first, which is why certain organs are especially vulnerable.
In the eyes, damaged blood vessels at the back of the retina can leak or swell, gradually leading to vision loss. In the kidneys, the tiny filtering units lose their ability to clean waste from your blood, potentially progressing to chronic kidney disease. Nerve damage is another hallmark of diabetes, often starting in the feet and hands as numbness, tingling, or pain that makes everyday activities difficult.
The cardiovascular system takes a broad hit. Diabetes damages blood vessel walls throughout the body, contributes to high blood pressure, and significantly increases the risk of heart attack, heart failure, and stroke. Blood vessel damage in the brain can also lead to memory problems over time. These complications aren’t inevitable. Keeping blood sugar well-controlled slows or prevents most of them.
How Diabetes Is Managed
Treatment looks different depending on the type. People with Type 1 diabetes take insulin multiple times a day, timed around meals and adjusted based on activity levels. Insulin can be delivered through a syringe, an insulin pen, an insulin pump worn on the body, or even an artificial pancreas system that automates much of the dosing. There is no pill alternative for Type 1.
Type 2 diabetes often starts with lifestyle changes. Eating balanced meals, limiting excess calories, staying physically active, sleeping well, and managing stress can all help lower blood sugar. For many people, though, lifestyle changes alone aren’t enough, and oral medications or injectable insulin become part of the routine. Some people with Type 2 eventually need insulin as their pancreas produces less of it over the years.
Gestational diabetes is typically managed through a healthy eating plan and moderate physical activity, such as 150 minutes of brisk walking per week. If that’s not enough to keep blood sugar in a safe range, insulin may be recommended for the remainder of the pregnancy.
Prediabetes and Prevention
Prediabetes affects an enormous number of people, over 115 million adults in the U.S. alone, and most don’t know they have it. The good news is that this stage responds remarkably well to straightforward lifestyle changes. Walking 30 minutes a day and cutting back on high-fat, high-sugar foods has been shown to reduce the risk of developing Type 2 diabetes by more than 50% in people with prediabetes.
A review of randomized trials following over 5,000 people with prediabetes for two to six years found that about 15% of those who made lifestyle changes developed diabetes, compared to 26% in the group that didn’t, a 42% reduction in risk. Even web-based programs that pair personalized eating plans with a single dietitian consultation have produced roughly a 45% drop in diabetes risk. These numbers are striking because they show that a relatively modest amount of daily movement and dietary adjustment can change the trajectory of the disease before it starts.