Diabetes is a chronic disease in which your blood sugar (glucose) stays too high because your body either can’t make enough insulin or can’t use the insulin it makes. Insulin is a hormone produced by your pancreas, and its job is to move sugar from your bloodstream into your cells, where it’s used for energy. When that system breaks down, sugar builds up in your blood and causes damage over time.
How Insulin Normally Works
Every time you eat, your body breaks food down into glucose, which enters your bloodstream. Your pancreas detects the rise in blood sugar and releases insulin in response. Insulin acts like a key: it signals your cells, especially muscle cells, to open tiny doorways (called glucose transporters) on their surface. These doorways sit dormant inside the cell until insulin arrives and triggers them to move to the cell wall, where they can pull glucose in.
Once insulin levels drop, those doorways retract back inside the cell and glucose uptake slows. This cycle keeps blood sugar in a narrow, healthy range throughout the day. In diabetes, the cycle is disrupted at one stage or another, and glucose stays stranded in the bloodstream instead of reaching the cells that need it.
Type 1 Diabetes
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 to take insulin every day for the rest of their lives because their body has permanently lost the ability to produce it.
Type 2 Diabetes
Type 2 diabetes is far more common and works differently. Your pancreas still makes insulin, at least initially, but your cells stop responding to it properly. This is called insulin resistance. Your muscles, liver, and fat cells essentially ignore insulin’s signal to open up and absorb glucose. The pancreas tries to compensate by producing more insulin, but over time it can’t keep up. Eventually, many people with Type 2 produce less and less insulin, and some stop producing it altogether.
Type 2 is more likely to develop in adults, though it’s becoming increasingly common in children and teenagers. Risk factors include excess weight, physical inactivity, and family history.
Gestational Diabetes
Some women develop diabetes during pregnancy, even if they’ve never had blood sugar problems before. This is called gestational diabetes. Hormonal changes during pregnancy can make cells more resistant to insulin, and if the pancreas can’t produce enough extra insulin to overcome that resistance, blood sugar rises. Screening typically happens between 24 and 28 weeks of pregnancy, though women with higher risk factors may be tested at their first prenatal visit. Gestational diabetes usually resolves after delivery, but it significantly raises the risk of developing Type 2 diabetes later in life.
Common Symptoms
The early warning signs of diabetes are driven by excess sugar in the blood. When your kidneys work overtime to filter out the extra glucose, you urinate more frequently. That fluid loss makes you unusually thirsty. Because your cells aren’t getting the glucose they need for fuel, you may feel persistent hunger and fatigue even when you’re eating enough.
Type 1 symptoms tend to come on quickly, over days or weeks. Type 2 develops gradually, and many people live with it for years without noticing. Blurry vision, slow-healing cuts, and tingling in the hands or feet are signs that blood sugar has been elevated for a while.
How Diabetes Is Diagnosed
Doctors use a few straightforward 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 as a percentage. A normal A1C is below 5.7%. Between 5.7% and 6.4% is considered prediabetes, a warning zone where blood sugar is elevated but not yet high enough for a diabetes diagnosis. An A1C of 6.5% or higher means diabetes.
A fasting blood glucose test checks your blood sugar after you haven’t eaten for at least eight hours. Normal is below 100 mg/dL, prediabetes falls between 100 and 125, and 126 or above indicates diabetes. A glucose tolerance test, where you drink a sugary solution and have your blood drawn two hours later, uses a threshold of 200 mg/dL. If your blood sugar is 200 mg/dL or higher at any random point during the day and you have symptoms, that alone can confirm the diagnosis.
What Happens if Blood Sugar Stays High
Chronically elevated blood sugar damages blood vessels and nerves throughout the body. The effects are widespread and serious, but they develop slowly, often over years.
- Heart and blood vessels: Diabetes makes it harder to control blood pressure and cholesterol, raising your risk of heart attack and stroke.
- Kidneys: High blood sugar gradually damages the kidneys’ filtering system. In severe cases, kidneys can lose function entirely, requiring dialysis or a transplant.
- Eyes: Damage to tiny blood vessels in the retina can cause vision problems, difficulty seeing at night, light sensitivity, and eventually blindness.
- Nerves: Nerve damage, especially in the feet and legs, causes pain, burning, tingling, or numbness. It can also affect digestion and sexual function.
These complications aren’t inevitable. Keeping blood sugar closer to the normal range through treatment and lifestyle changes dramatically lowers the risk of all of them. That’s why early detection and consistent management matter so much, particularly for Type 2 diabetes and prediabetes, where changes in diet, physical activity, and weight can make a measurable difference in blood sugar levels.