Diabetes Mellitus

Core Concepts

Normal glucose regulation: the two-sided pancreas

After a meal, blood glucose rises; beta cells release insulin, which tells muscle, fat, and liver cells to take up glucose for energy or storage, lowering blood glucose. Between meals, glucagon from the alpha cells triggers the liver to release stored glucose, preventing hypoglycemia. This insulin–glucagon balance keeps blood glucose stable. Diabetes is the breakdown of this balance — either the insulin side (production) or the response side (resistance) fails.

Types of diabetes: different failures, different paths

Type 1 diabetes is an autoimmune condition in which the immune system destroys the pancreatic beta cells, leading to near-total insulin deficiency. It usually appears in childhood or young adulthood, onset is often rapid, and it requires lifelong insulin therapy — the body simply cannot make it. Type 2 diabetes begins with insulin resistance — cells respond poorly to insulin — and progresses as the pancreas tires and produces less. It typically develops in adulthood (increasingly in younger people), onset is gradual, and management begins with lifestyle change and often oral medications before insulin is needed. Gestational diabetes is glucose intolerance that first appears in pregnancy and usually resolves after delivery, though it raises the person's future risk of type 2 diabetes. A category of "other specific types" includes drug-induced and genetic causes. Prediabetes — blood glucose above normal but below the diabetes threshold — is the high-risk warning zone where lifestyle change can prevent or delay diabetes.

Why hyperglycemia causes symptoms: the classic triad

When blood glucose exceeds what the kidneys can reabsorb, glucose spills into the urine and drags water with it — polyuria (excessive urination), which causes dehydration and thirst — polydipsia (excessive drinking). Because cells cannot take up glucose without insulin action, the body starves at the cellular level despite high blood glucose, triggering hunger — polyphagia — and, when the body breaks down fat and protein for fuel, weight loss and fatigue. This triad (polyuria, polydipsia, polyphagia) plus fatigue and weight loss is the classic presentation of new-onset diabetes, and any nurse can recognize it.

Acute complications: the three emergencies

• Hypoglycemia (low blood glucose) — too much insulin (or other glucose-lowering medication), too little food, or extra activity. Symptoms include shakiness, sweating, confusion, irritability, hunger, and rapid heart rate; severe hypoglycemia can cause loss of consciousness and seizures. It develops fast. Treatment follows the facility's hypoglycemia protocol (oral fast-acting carbohydrate if the person can safely swallow; emergency measures if not) — nurses must know where the protocol is and act promptly, then find why it happened.
• Diabetic ketoacidosis (DKA) — profound insulin deficiency (most often in type 1), in which the body burns fat for fuel and produces ketones, acidifying the blood. It develops over hours to days with extreme hyperglycemia, dehydration, and a fruity breath odor from ketones; it is a medical emergency requiring hospital care. Often triggered by missed insulin, infection, or new-onset disease.
• Hyperosmolar hyperglycemic state (HHS) — extreme hyperglycemia (typically in type 2) causing severe dehydration without the ketone buildup of DKA; develops more slowly but is equally serious.

The teaching takeaway: hypoglycemia is the fast emergency the patient must recognize and treat at home; DKA and HHS are the slow emergencies that land people in the hospital.

Chronic complications: the long toll of hyperglycemia

Years of hyperglycemia damage blood vessels. Microvascular (small-vessel) complications include retinopathy (eye damage → vision loss), nephropathy (kidney damage → CKD, linking back to Chapter 20), and neuropathy (nerve damage → numbness, pain, and loss of protective sensation, especially in the feet — which, combined with poor circulation, is why foot ulcers and amputations happen). Macrovascular (large-vessel) complications include accelerated atherosclerosis — heart attack, stroke, and peripheral artery disease. The unifying nursing message: good glucose control over time reduces these risks, which is why every day of good management counts.

Monitoring and treatment concepts

Management is a four-legged stool. (1) Monitoring: self-monitoring of blood glucose (SMBG) with a meter gives the day-to-day picture; A1C (glycated hemoglobin) reflects average glucose over roughly the previous 2–3 months and is the long-term gauge. (2) Healthy eating and activity: carbohydrate awareness, regular meals, and physical activity work with the body's own insulin. (3) Medications: oral agents and non-insulin injectables address insulin resistance, production, or absorption in type 2; insulin — given by injection or pump, in several types that differ in how fast they act and how long they last — is essential in type 1 and often needed in type 2 over time. (4) Preventive care: regular eye exams, kidney function checks, foot exams, and cardiovascular risk management. This topic deliberately gives no doses or targets — they vary with guidelines, products, and the individual, and must be verified with current references and the provider.

The nursing role: teaching that changes outcomes

Daily nursing care includes: blood glucose monitoring per orders and reporting concerning values; watching for and treating hypoglycemia per protocol; assessing the feet for breaks, redness, or numbness; coordinating meals and medication timing; and teaching — at every opportunity — self-monitoring, medication administration (including correct insulin technique and storage per the manufacturer), sick-day rules (never stop insulin when ill; check glucose more often; seek help for persistent vomiting or very high glucose), foot care (daily inspection, proper footwear, prompt reporting of any injury), and when to call for help. Equally important: speak in plain language, use person-first terms, and address the emotional burden — diabetes burnout is real, and judgment is the enemy of adherence.

Clinical Scenario: The Skipped Breakfast

Mr. Okafor, 47, has type 2 diabetes on insulin. He is admitted for observation after surgery and is NPO (nothing by mouth) awaiting a test. At 10 a.m. the nurse finds him diaphoretic, shaky, and confused. The nurse recognizes hypoglycemia, checks his glucose per protocol, and — because Mr. Okafor is confused and cannot safely swallow — follows the facility's hypoglycemia emergency protocol while calling for assistance. After treatment, the glucose rises and Mr. Okafor's mentation clears. The nurse then reviews the situation: his usual morning insulin was given, but he had not eaten due to NPO — a mismatch of insulin and food. She documents the episode, reports it to the provider to review the insulin plan for NPO days, and teaches Mr. Okafor that skipping meals, illness, and fasting all change how much insulin he needs. The episode was treated and the cause found — that second step is what prevents the next one.

Common Confusions