Diabetes mellitus

Diabetes Mellitus

Clinical overview of diabetes mellitus showing the pancreas, insulin production, blood glucose, and major organs affected by chronic hyperglycaemia.

1. Introduction

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by persistent hyperglycaemia, meaning that the level of glucose in the blood remains higher than normal. It develops when the body does not produce enough insulin, does not use insulin effectively, or both.

Insulin is a hormone produced by the beta cells of the pancreas. Its major function is to help glucose move from the bloodstream into body cells, where it can be used to produce energy. When insulin is absent, insufficient, or ineffective, glucose accumulates in the blood while many cells are unable to use it properly.

Diabetes is important in nursing because uncontrolled hyperglycaemia can gradually damage blood vessels and nerves. Over time, this may affect the eyes, kidneys, heart, brain, peripheral nerves and feet. Acute complications such as diabetic ketoacidosis and hyperosmolar hyperglycaemic state can also become life-threatening.

For nursing practice, diabetes management is therefore not limited to giving insulin or checking blood glucose. It includes assessment, medication administration, nutrition, exercise, monitoring, prevention of complications, foot care, patient education and recognition of emergencies.

2. Classification of Diabetes Mellitus

Comparison of type 1 diabetes, type 2 diabetes, gestational diabetes, and other specific forms of diabetes.

3. Pathophysiology

Understanding the pathophysiology makes diabetes much easier to remember. Normally, carbohydrates are broken down into glucose. Glucose enters the bloodstream and stimulates pancreatic beta cells to release insulin.

Insulin acts like a key that facilitates glucose entry into many body cells. When insulin is inadequate or ineffective, glucose remains in the bloodstream.

Diagram showing normal insulin-mediated glucose uptake compared with impaired glucose utilization in diabetes.

Persistent hyperglycaemia produces several important effects. Excess glucose increases the osmotic concentration of blood. The kidneys attempt to remove excess glucose through urine. Because glucose draws water with it, the person develops polyuria, or excessive urination. Fluid loss causes dehydration, which stimulates thirst and produces polydipsia.

In severe insulin deficiency, cells cannot adequately use glucose for energy. The body begins breaking down fat. Fat breakdown produces ketone bodies, which can accumulate and cause metabolic acidosis. This mechanism is central to diabetic ketoacidosis.

Chronic hyperglycaemia also damages vascular and neural tissues. Small blood vessels are particularly vulnerable, producing microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Damage to larger blood vessels contributes to macrovascular complications, including coronary artery disease, cerebrovascular disease and peripheral arterial disease.

4. Clinical Manifestations

Infographic illustrating the classic three Ps of diabetes: polyuria, polydipsia, and polyphagia, along with other common symptoms.

The classic symptoms of diabetes are often remembered as the three Ps: polyuria, polydipsia and polyphagia.

• Unexplained weight loss, particularly in type 1 diabetes.
• Fatigue and weakness.
• Blurred vision.
• Slow wound healing.
• Recurrent infections.
• Recurrent urinary or genital infections.
• Pruritus.
• Numbness or tingling of the extremities.
• Dry skin.
• Poor concentration.
• Irritability.

Some patients, especially those with type 2 diabetes, may have few or no obvious symptoms for a long period.

5. Diagnostic Criteria

Diabetes is diagnosed using laboratory testing. Common diagnostic approaches include HbA1c, fasting plasma glucose, oral glucose tolerance testing, and appropriately interpreted random plasma glucose.

6. Common Investigations in a Patient With Diabetes

• Blood glucose: Used for immediate assessment and monitoring of glycaemic control.
• HbA1c: Used to assess longer-term glycaemic control.
• Urine examination: May identify glucose, ketones, protein, or evidence of infection.
• Renal assessment: Serum creatinine and estimated glomerular filtration rate help evaluate kidney function.
• Urine albumin assessment: Helps detect early diabetic kidney disease.
• Lipid profile: Diabetes increases cardiovascular risk, so assessment of cholesterol and triglycerides is important.
• Electrolytes and acid-base studies: Particularly important when diabetic ketoacidosis or another acute metabolic emergency is suspected.
• Eye examination: Used to detect diabetic retinopathy.
• Foot and neurological assessment: Used to identify neuropathy, skin breakdown, deformity, and vascular problems.

7. Acute Complications

Clinical comparison of hypoglycaemia, diabetic ketoacidosis, and hyperosmolar hyperglycaemic state, highlighting their major features.

The major acute diabetic emergencies are hypoglycaemia, diabetic ketoacidosis (DKA), and hyperosmolar hyperglycaemic state (HHS).

Hypoglycaemia

Hypoglycaemia occurs when blood glucose falls below the level required for normal physiological function. It commonly results from excessive insulin or glucose-lowering medication, inadequate food intake, increased physical activity, alcohol use, or a combination of these factors.

• Sweating.
• Trembling.
• Hunger.
• Palpitations.
• Anxiety.
• Dizziness.
• Weakness.
• Confusion.
• Difficulty speaking.
• Behavioural changes.
• Seizures.
• Loss of consciousness.

For a conscious patient who can safely swallow, rapid-acting carbohydrate is generally used and glucose is reassessed afterward according to the clinical protocol.

8. Diabetic Ketoacidosis

Diabetic ketoacidosis (DKA) is a serious metabolic emergency characterized by the combination of diabetes or hyperglycaemia, ketone production, and metabolic acidosis.

It is particularly associated with type 1 diabetes but can occur in other circumstances. When insulin is severely deficient, the body cannot adequately use glucose. Fat is broken down, producing ketones. Accumulation of ketones causes metabolic acidosis.

Pathophysiology of diabetic ketoacidosis showing insulin deficiency, fat breakdown, ketone production, dehydration, and metabolic acidosis.

• Polyuria.
• Polydipsia.
• Dehydration.
• Nausea and vomiting.
• Abdominal pain.
• Weakness.
• Altered mental status.
• Deep, rapid breathing.
• Fruity or acetone-like breath.

Treatment generally involves carefully monitored fluid replacement, insulin therapy, electrolyte management, particularly potassium, and treatment of the precipitating cause.

Common precipitating factors include infection, inadequate insulin administration, newly diagnosed diabetes, and other physiological stressors.

Nursing Priorities in DKA

9. Hyperosmolar Hyperglycaemic State

Hyperosmolar hyperglycaemic state (HHS) is another severe diabetic emergency. It is most commonly associated with type 2 diabetes. The patient develops marked hyperglycaemia, profound dehydration, and increased serum osmolality, usually without the prominent ketoacidosis seen in DKA.

• Extreme thirst.
• Polyuria initially.
• Severe dehydration.
• Weakness.
• Confusion.
• Neurological abnormalities.
• Seizures or coma in severe cases.

Treatment focuses on careful fluid replacement, insulin when indicated, correction of electrolyte abnormalities, and management of the underlying precipitating condition.

10. Chronic Complications

Body map showing major microvascular and macrovascular complications of long-standing diabetes.

The risk of these complications increases with prolonged hyperglycaemia and other cardiovascular risk factors.

11. Diabetic Retinopathy

Long-term hyperglycaemia damages retinal blood vessels. Early disease may produce no symptoms, which is why regular eye screening is important.

• Blurred vision.
• Floaters.
• Visual field changes.
• Reduced vision.
• Severe visual impairment.

Nurses should emphasize the importance of regular eye examinations and good glycaemic, blood pressure, and lipid control.

12. Diabetic Kidney Disease

Diabetes can damage the glomerular filtration system of the kidneys. An early marker may be increased urinary albumin excretion. Progressive disease can lead to declining kidney function and eventually kidney failure.

• Monitor blood pressure.
• Monitor renal function.
• Assess urinary albumin as ordered.
• Monitor fluid status.
• Observe medication effects and renal dosing considerations.

Patients should understand that kidney disease can progress silently, making screening particularly important.

13. Diabetic Neuropathy

Persistent hyperglycaemia can damage peripheral nerves. The patient may experience numbness, tingling, burning pain, reduced sensation, altered temperature perception, or weakness in advanced cases.

Loss of protective sensation is particularly dangerous because a patient may develop a blister, burn, or wound without noticing it. This is one reason diabetic foot care is so important.

14. Diabetic Foot

Clinical illustration of diabetic foot risk factors showing neuropathy, poor circulation, pressure, trauma, ulceration, and impaired wound healing.

The diabetic foot results from a combination of neuropathy, vascular disease, pressure, trauma, and impaired wound healing.

A patient with neuropathy may not feel a small injury. If blood circulation is poor, oxygen and nutrients may not reach the wound adequately. Hyperglycaemia can further impair immune function and healing.

Therefore, a small foot injury can progress to ulceration, infection and, in severe cases, tissue necrosis or amputation.

Diabetic Foot Assessment

• Cuts.
• Blisters.
• Ulcers.
• Redness.
• Swelling.
• Calluses.
• Fissures.
• Discoloration.
• Nail abnormalities.
• Signs of infection.

Assess sensation and peripheral circulation as appropriate. Patients should be taught to inspect their feet every day, keep them clean and dry, wear properly fitting footwear, avoid walking barefoot, and seek medical attention promptly for wounds or signs of infection.

15. Management of Diabetes Mellitus

Integrated diabetes management model showing nutrition, physical activity, medication, glucose monitoring, education, and prevention of complications.

Diabetes management has several interconnected components: nutrition + physical activity + medication + glucose monitoring + education + complication prevention.

The treatment plan must be individualized according to diabetes type, age, comorbidities, medications, lifestyle, pregnancy status, and risk of hypoglycaemia.

16. Medical Nutrition Therapy

Nutrition therapy is not simply a matter of completely avoiding sugar. A balanced dietary pattern should provide appropriate amounts of carbohydrates, protein, fats, fibre, vitamins, and minerals.

• Portion control.
• Carbohydrate awareness.
• High-fibre foods.
• Balanced meals.
• Appropriate meal timing.
• Limiting excessive refined carbohydrates.
• Avoiding excessive saturated and trans fats.
• Individualized calorie requirements.

A dietitian or diabetes educator can help develop an individualized meal plan.

17. Physical Activity

Regular physical activity improves insulin sensitivity and helps with glucose control, cardiovascular health, and weight management.

For many adults, a practical target is at least 150 minutes of moderate-intensity aerobic activity per week, distributed across several days, when medically appropriate. Resistance exercise can also improve muscle strength and insulin sensitivity.

Patients using insulin or medications that can cause hypoglycaemia should be taught how physical activity can alter glucose requirements and how to recognize and manage hypoglycaemia.

18. Pharmacological Management

Medication depends on the type of diabetes and the patient's clinical condition.

Insulin

Insulin is essential in type 1 diabetes and is also used in many people with type 2 diabetes when needed.

Educational illustration of insulin administration using a pen and syringe, including safe injection-site rotation.

Nursing Responsibilities With Insulin

1. Verify the prescribed insulin, dose, and timing.
2. Confirm the patient's blood glucose as ordered.
3. Check the insulin product carefully.
4. Use the correct administration technique.
5. Rotate injection sites according to the patient's treatment plan.
6. Monitor for hypoglycaemia.
7. Document administration and relevant glucose readings.
8. Educate the patient regarding storage, injection technique, and recognition of hypoglycaemia.

Oral and Non-Insulin Glucose-Lowering Drugs

19. Blood Glucose Monitoring

Blood glucose monitoring helps determine whether treatment is working and can identify hypoglycaemia or hyperglycaemia.

• Capillary blood glucose testing.
• Continuous glucose monitoring.
• Pre-meal measurements.
• Post-meal measurements.
• Bedtime testing.
• Testing during symptoms.
• Testing before or after exercise when indicated.

The nurse must document readings accurately and recognize patterns rather than focusing on a single isolated value.

20. Nursing Assessment

History

• Duration and type of diabetes.
• Current medications.
• Insulin use.
• Dietary pattern.
• Physical activity.
• Previous hypoglycaemia.
• Previous DKA or HHS.
• Family history.
• Foot problems.
• Vision changes.
• Renal problems.
• Cardiovascular disease.
• Recent infection.
• Medication adherence.

Physical Assessment

• Vital signs.
• Hydration status.
• Weight.
• Skin.
• Injection sites.
• Feet.
• Peripheral pulses.
• Sensation.
• Vision-related complaints.
• Neurological status.
• Signs of infection.

21. Nursing Diagnoses

• Risk for unstable blood glucose level.
• Deficient knowledge regarding diabetes self-management.
• Risk for infection.
• Impaired skin integrity.
• Risk for impaired skin integrity.
• Fatigue.
• Imbalanced nutrition.
• Acute confusion associated with severe glucose abnormalities.
• Risk for injury related to hypoglycaemia or neuropathy.

Nursing diagnoses should always be based on the individual patient's assessment rather than applied automatically to every patient with diabetes.

22. Patient Education

Diabetes self-management education scene showing glucose monitoring, medication, nutrition, exercise, foot care, and follow-up.

23. Nursing Care During Hospitalization

Hospitalized patients with diabetes require close monitoring because infection, surgery, stress, altered nutrition, and medications such as corticosteroids can significantly change glucose levels.

1. Monitor glucose according to the prescribed schedule.
2. Administer medications safely.
3. Coordinate insulin administration with nutrition when required.
4. Observe for hypoglycaemia and hyperglycaemia.
5. Maintain hydration as appropriate.
6. Monitor for infection.
7. Document glucose readings, medications, nutrition, and clinically important changes.

During periods of poor oral intake, medication requirements may change. Therefore, insulin or other glucose-lowering medication should not be independently withheld or altered without appropriate clinical direction.

24. Diabetes and Wound Healing

Diagram showing how hyperglycaemia, impaired immunity, neuropathy, vascular disease, and poor perfusion contribute to delayed wound healing.

Diabetes is particularly important in nursing wound care. Persistent hyperglycaemia can impair immune responses, vascular function, and tissue repair. Peripheral neuropathy may cause repeated unnoticed trauma, while peripheral arterial disease may reduce tissue perfusion.

Assessment of a Diabetic Wound

• Location.
• Size.
• Depth.
• Wound bed.
• Exudate.
• Odour.
• Surrounding skin.
• Signs of infection.
• Perfusion.
• Sensation.
• Pressure or mechanical causes.

Wound management must address both the wound and the underlying metabolic and vascular factors.

25. Important Nursing Emergencies

Emergency recognition chart comparing hypoglycaemia, DKA, and HHS with their characteristic clinical warning signs.

26. Prevention of Complications

Good diabetes care aims not only to lower glucose but also to reduce overall cardiovascular and organ damage.

• Maintain individualized glycaemic targets.
• Control blood pressure.
• Manage lipid levels.
• Stop smoking.
• Maintain regular physical activity.
• Follow a healthy nutrition plan.
• Attend regular eye assessments.
• Complete recommended kidney screening.
• Attend regular foot assessments.
• Follow recommended vaccination schedules.
• Treat infections early.
• Maintain regular healthcare follow-up.

27. Quick Clinical Summary

28. Key Takeaway for Nursing Students

Final nursing concept map connecting diabetes pathophysiology, complications, treatment, monitoring, emergency recognition, and patient education.

Diabetes should be understood as a whole-body disease rather than simply a high blood sugar disorder.

The central problem is abnormal glucose regulation, but the consequences can involve nearly every major organ system. Nursing care therefore extends from checking a bedside glucose value to recognizing DKA, preventing pressure injuries, assessing peripheral circulation, administering insulin safely, teaching foot care, and helping the patient develop sustainable self-management habits.