Diabetes mellitus is a group of metabolic diseases characterized by elevated blood sugar (hyperglycemia), resulting from defects in insulin secretion, insulin action, or both. It is one of the most common chronic diseases worldwide, affecting over 37 million Americans — roughly 1 in 10 people.
The Role of Insulin
To understand diabetes, it helps to understand insulin's role. When you eat, carbohydrates are broken down into glucose, which enters the bloodstream. In response, the pancreas releases insulin — a hormone that acts as a "key" allowing glucose to enter cells, where it is used for energy. Without adequate insulin action, glucose accumulates in the blood while cells are starved of energy.
Types of Diabetes
- Type 1 Diabetes (T1D) — An autoimmune condition in which the immune system destroys insulin-producing beta cells in the pancreas. Patients require lifelong insulin therapy. Typically diagnosed in childhood or young adulthood, though it can occur at any age.
- Type 2 Diabetes (T2D) — The most common form (~90–95% of cases). Develops due to progressive insulin resistance combined with relative insulin deficiency. Strongly associated with obesity, inactivity, and genetic factors. Usually managed with lifestyle changes and oral/injectable medications, sometimes including insulin.
- Gestational Diabetes Mellitus (GDM) — Develops during pregnancy due to insulin resistance from placental hormones. Requires treatment to protect fetal outcomes. Women with GDM have a significantly increased risk of developing T2D later in life.
- Other specific types — Including MODY (Maturity-Onset Diabetes of the Young), medication-induced diabetes, and diabetes from pancreatic disease.
Symptoms of Diabetes
Classic symptoms of elevated blood sugar include:
- Increased thirst (polydipsia)
- Frequent urination (polyuria)
- Unexplained weight loss
- Blurry vision
- Fatigue
- Slow-healing wounds
- Frequent infections
- Tingling or numbness in feet or hands
Type 2 diabetes often develops gradually with few symptoms — many people have diabetes for years before diagnosis. Type 1 diabetes typically presents more acutely.
How Is Diabetes Diagnosed?
| Test | Diabetes | Pre-Diabetes | Normal |
|---|---|---|---|
| Fasting glucose | ≥126 mg/dL | 100–125 mg/dL | <100 mg/dL |
| A1C | ≥6.5% | 5.7–6.4% | <5.7% |
| 2-hr glucose (OGTT) | ≥200 mg/dL | 140–199 mg/dL | <140 mg/dL |
| Random glucose (with symptoms) | ≥200 mg/dL | — | — |
Why Diabetes Management Matters
Chronically elevated blood sugar damages blood vessels and nerves throughout the body, leading to serious long-term complications including heart disease, stroke, kidney failure, blindness, and neuropathy (nerve damage). The great news: with proper treatment and monitoring, these complications can be prevented or significantly delayed.
Key Takeaways
- Diabetes is extremely common — 1 in 10 Americans has it, and many are undiagnosed
- Type 2 is the most common form; Type 1 requires lifelong insulin
- A1C is the key long-term measure of blood sugar control
- With proper treatment, diabetes complications can be prevented
- Board-certified endocrinologists specialize in optimal diabetes management