Glucose

1. Importance of Glucose in the Body

Glucose is the primary source of energy, especially for:

• Brain

• Red blood cells

• Renal medulla

• Exercising muscle

Normal fasting plasma glucose: 70–99 mg/dL

2. Clinical Significance

A. Diagnosis of Diabetes Mellitus

Measurement of blood glucose is essential for diagnosing:

• Type 1 Diabetes Mellitus

• Type 2 Diabetes Mellitus

• Gestational Diabetes

Diagnostic Criteria (ADA)

• Fasting plasma glucose ≥ 126 mg/dL

• Random glucose ≥ 200 mg/dL with symptoms

• 2-hour OGTT ≥ 200 mg/dL

• HbA1c ≥ 6.5%

B. Hyperglycemia (High Blood Glucose)

Occurs in:

• Diabetes mellitus

• Cushing’s syndrome

• Hyperthyroidism

• Acute stress (trauma, infection)

• Pancreatitis

Severe hyperglycemia may lead to:

• Diabetic ketoacidosis (DKA)

• Hyperosmolar hyperglycemic state (HHS)

• Long-term microvascular and macrovascular complications

C. Hypoglycemia (Low Blood Glucose)

Defined as glucose < 70 mg/dL

Causes:

• Excess insulin or oral hypoglycemics

• Insulinoma

• Liver disease

• Adrenal insufficiency

• Starvation

Symptoms:

• Sweating

• Tremors

• Palpitations

• Confusion

• Seizures

• Coma

D. Monitoring of Therapy

Blood glucose testing is used to:

• Monitor insulin therapy

• Adjust oral antidiabetic drugs

• Prevent complications

• Assess glycemic control in ICU patients

E. Screening & Special Situations

• Screening during pregnancy (OGTT)

• Monitoring critically ill patients

• Evaluating endocrine disorders

• Assessing metabolic syndrome

3. Specimen & Methods (Brief)

• Sample: Plasma (fluoride tube preferred)

• Methods:

  • Glucose oxidase method

  • Hexokinase method (reference method)

  • Point-of-care glucometers