Introduction to Diabetes

Core Concepts

Glucose and insulin: the normal partnership

Glucose is the body's preferred fuel, and blood glucose is kept in a narrow range by two opposing hormone families from the pancreatic islets:

• Insulin (from beta cells) is the "storage" hormone. After a meal, rising glucose triggers insulin release; insulin then tells muscle and fat cells to take up glucose (by moving glucose transporters to the cell surface), tells the liver to store glucose as glycogen, and promotes fat and protein storage. It is the only hormone that lowers blood glucose.
• Glucagon (from alpha cells) is the "release" hormone. When glucose falls, glucagon tells the liver to break down glycogen and release glucose. Other counter-regulatory signals (such as epinephrine and cortisol) back this up during stress or fasting.

The balance keeps fuel available to the brain — which cannot store glucose and depends on a steady blood supply — while preventing glucose from lingering too high in the blood.

The major types of diabetes

Type 1 diabetes is an autoimmune condition in which the immune system destroys the insulin-producing beta cells. People with type 1 produce little or no insulin and need exogenous (injected) insulin from diagnosis — often presenting acutely with weight loss, excessive thirst and urination, and sometimes ketoacidosis. It commonly begins in childhood, adolescence, or young adulthood, though it can appear at any age.

Type 2 diabetes is far more common and usually develops in adulthood, though it is increasingly seen in younger people. The core defects are insulin resistance (cells respond poorly to insulin, so the pancreas must secrete more to compensate) combined with relative insulin deficiency (the overworked beta cells eventually cannot keep up). Progression is gradual; many people have years of elevated glucose before diagnosis, which is why screening and early detection matter. Management can start with lifestyle change and oral medications, but many people with type 2 eventually need injectable therapy, including insulin — this is not a "failure" of the person, it is the natural course of the disease.

Gestational diabetes develops during pregnancy in people who did not have diabetes before. Pregnancy hormones increase insulin resistance, and when the pancreas cannot compensate, glucose rises. It matters for the pregnancy itself — glucose crosses the placenta and affects fetal growth — and it strongly predicts future type 2 diabetes in the parent, so follow-up testing after delivery is standard.

Other specific types exist — including diabetes from pancreatic disease, certain medications, genetic syndromes, and monogenic forms — reminding us that "diabetes" is a syndrome with multiple causes, not a single disease.

Acute complications: the emergencies

• Diabetic ketoacidosis (DKA): most often with type 1 (though it can occur in type 2), severe insulin deficiency forces the body to burn fat for fuel, producing ketones and acid. Classic features include high glucose, ketones, dehydration, and rapid breathing. It is a medical emergency requiring fluids, electrolytes, and insulin under close monitoring.
• Hyperosmolar hyperglycemic state (HHS): seen mainly in type 2, extreme hyperglycemia causes severe dehydration without the same degree of ketosis — the person may become profoundly dehydrated and confused.
• Hypoglycemia: the acute complication of treatment. Insulin or other glucose-lowering drugs can drive glucose too low, producing sweating, tremor, confusion, and, if severe, loss of consciousness. It is treatable — fast-acting carbohydrate or, if the person cannot swallow safely, emergency treatment — and preventing it is a central goal of therapy.

The treatment distinction matters: hyperglycemia builds over hours to days; hypoglycemia can develop in minutes. Nurses teach people the warning signs of both.

Chronic complications: the damage of years

Elevated glucose damages blood vessels in two patterns:

• Microvascular disease (small vessels): diabetic retinopathy (vision loss), nephropathy (kidney disease, progressing to kidney failure), and neuropathy (nerve damage — numbness, pain, and loss of protective sensation in the feet, which is why foot care and screening are essential).
• Macrovascular disease (large vessels): accelerated atherosclerosis leading to heart attack, stroke, and peripheral artery disease.

These complications accumulate silently over years, which is why "control matters" is not a slogan but a mechanism: better glucose control reduces the risk of these complications. Blood pressure, lipids, and tobacco use are managed aggressively alongside glucose because they share the same blood-vessel targets.

How diabetes is assessed and monitored

Diagnosis and monitoring rely on blood tests — including fasting glucose, oral glucose tolerance testing, and A1C (a measure of average glucose over the prior two to three months). A1C is also the standard tool for tracking long-term control. Exact diagnostic thresholds and treatment targets are set by organizations such as the American Diabetes Association and vary by guideline version, population, and individual circumstances — nurses should verify current criteria rather than recite them from memory. Monitoring also includes checking for complications: blood pressure, foot exams, eye exams, and kidney function labs, on schedules determined by guidelines and the person's risk.

Person-first language is a professional standard throughout: "a person with diabetes," not "a diabetic." The person is not the disease, and the language of care shapes the care itself.

Common Confusions