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. Without enough working insulin, sugar builds up in your blood and starves your cells of fuel. About 40.1 million people in the United States have diabetes, roughly 1 in every 8, and more than 1 in 4 of them don’t know it.
How Insulin Normally Works
After you eat, your body breaks food down into glucose, a simple sugar that enters your bloodstream. Rising blood sugar signals your pancreas to release insulin. Insulin then travels through your blood and tells your cells to open up special glucose transporters on their surfaces. In muscle and fat tissue, these transporters sit inside the cell doing nothing until insulin arrives. Once insulin binds to the cell, those transporters move to the cell’s outer wall, where they pull glucose in. The cell gets energy, and your blood sugar drops back to normal.
When this system breaks down, glucose has nowhere to go. It accumulates in your blood, and over time that excess sugar damages blood vessels, nerves, and organs throughout your body.
Type 1 Diabetes
Type 1 diabetes is an autoimmune disease. Your immune system mistakenly attacks the insulin-producing cells in your pancreas and destroys them. The result is a near-complete inability to make insulin. Without daily insulin from injections or a pump, a person with Type 1 diabetes cannot survive.
Type 1 often appears in childhood, frequently between ages 4 and 6, though it can develop at any age. It accounts for a smaller share of all diabetes cases, roughly 5 to 10 percent. The exact trigger isn’t fully understood, but genetics and environmental factors both play a role.
Type 2 Diabetes
Type 2 diabetes is far more common and works differently. Your pancreas still produces insulin, at least initially, but your cells stop responding to it properly. This is called insulin resistance. Think of it as the locks on your cells becoming jammed: insulin (the key) is there, but it can’t open the door efficiently. Your pancreas compensates by producing even more insulin, flooding the system with extra keys. Over time, though, this overworked pancreas burns out and gradually makes less and less insulin. Eventually it may stop producing insulin altogether.
Type 2 diabetes is more common in adults, but it’s increasingly diagnosed in children and teenagers, largely driven by rising rates of obesity and sedentary lifestyles.
Gestational Diabetes
Gestational diabetes develops during pregnancy in women who didn’t have diabetes before. Hormonal changes during pregnancy can make cells more resistant to insulin, and some women’s bodies can’t produce enough extra insulin to compensate. It typically resolves after delivery, but it raises the risk of developing Type 2 diabetes later in life for both the mother and child.
Prediabetes: The Warning Stage
Prediabetes means your blood sugar is higher than normal but not high enough for a diabetes diagnosis. It’s a critical window because lifestyle changes at this stage, like losing a moderate amount of weight and getting regular physical activity, can cut your risk of developing Type 2 diabetes by 58 percent. For people over 60, that risk reduction climbs to 71 percent. Without changes, prediabetes frequently progresses to full Type 2 diabetes.
Common Symptoms
Many people with diabetes, especially Type 2, have no obvious symptoms in the early stages. When blood sugar climbs high enough, the most recognizable signs are frequent urination and increased thirst. The reason is straightforward: when there’s too much sugar in your blood, your kidneys can’t reabsorb it all. The excess sugar spills into your urine and pulls water along with it, so you urinate more. Losing all that fluid makes you dehydrated, which triggers intense thirst.
Other common symptoms include:
- Unexplained weight loss, especially in Type 1, because your cells can’t access glucose for energy and your body starts breaking down fat and muscle instead
- Fatigue, since your cells are starved of their primary fuel
- Blurred vision, caused by fluid shifts in the lens of your eye
- Slow-healing cuts or frequent infections
- Numbness or tingling in your hands or feet
How Diabetes Is Diagnosed
Doctors use a few straightforward blood tests. The numbers below come from the American Diabetes Association’s current diagnostic criteria:
- A1C test: Measures your average blood sugar over the past 2 to 3 months. Normal is below 5.7%. Prediabetes falls between 5.7% and 6.4%. Diabetes is 6.5% or higher.
- Fasting blood sugar: Taken after you haven’t eaten for at least 8 hours. Normal is below 100 mg/dL. Prediabetes is 100 to 125 mg/dL. Diabetes is 126 mg/dL or higher.
- Oral glucose tolerance test: Measures blood sugar two hours after drinking a sugary solution. Normal is below 140 mg/dL. Prediabetes is 140 to 199 mg/dL. Diabetes is 200 mg/dL or higher.
A single abnormal result is usually confirmed with a repeat test before a formal diagnosis is made.
Long-Term Complications
Persistently high blood sugar damages the body in two broad ways: it harms small blood vessels (affecting the eyes, kidneys, and nerves) and large blood vessels (raising the risk of heart attack, stroke, and poor circulation in the legs).
A large study tracking people with Type 2 diabetes over 15 years found that nerve damage in the hands and feet was the most frequently developing complication, followed closely by kidney disease. Both tended to appear within about 3 years of diagnosis. Heart-related complications, including heart failure and cardiovascular events like heart attack and stroke, were also significant risks. More severe outcomes like kidney failure requiring dialysis or amputation took longer to develop, typically around 5 years, but were devastating when they occurred.
The good news is that keeping blood sugar well controlled dramatically reduces the risk of all these complications.
Managing Blood Sugar
The goal of diabetes management is keeping blood sugar as close to normal as possible. The American Diabetes Association recommends most adults with diabetes aim for an A1C below 7%, a pre-meal blood sugar between 80 and 130 mg/dL, and a reading below 180 mg/dL one to two hours after starting a meal. These targets get adjusted based on your age, overall health, and individual circumstances.
For Type 1 diabetes, management always involves insulin, delivered through injections or an insulin pump, combined with monitoring blood sugar throughout the day. For Type 2 diabetes, treatment often starts with lifestyle changes: eating patterns that limit blood sugar spikes, regular physical activity, and weight loss if needed. Many people with Type 2 eventually need medication as well, and some progress to needing insulin over time as their pancreas produces less of it.
When Blood Sugar Becomes an Emergency
Extremely high blood sugar can become life-threatening. One dangerous condition involves severe dehydration combined with very high blood sugar, more common in Type 2 diabetes. Symptoms escalate from increased thirst and urination to weakness, confusion, fever, seizures, and eventually coma. This is a medical emergency. Another acute crisis, more common in Type 1, occurs when the body starts breaking down fat so rapidly that it produces toxic acids in the blood, leading to nausea, vomiting, abdominal pain, and a fruity smell on the breath. Both situations require emergency treatment.
Recognizing these warning signs matters because early action, getting to an emergency room quickly, can prevent permanent harm.