What are the symptoms of hyperglycemia in a patient with diabetes?

Symptoms of Hyperglycemia

The classic symptoms of hyperglycemia include polyuria (excessive urination), polydipsia (excessive thirst), unintentional weight loss, polyphagia (increased hunger), and blurred vision, which occur when blood glucose levels become significantly elevated and persist over time. 1

Primary Symptoms

Osmotic Symptoms

• Polyuria develops when blood glucose exceeds the renal threshold for reabsorption (typically around 180 mg/dL), causing glucose to spill into urine and pull water with it through osmotic forces 2
• Polydipsia occurs as a compensatory response to fluid loss from osmotic diuresis and resulting dehydration 1
• Unintentional weight loss results from two mechanisms: fluid loss through osmotic diuresis and breakdown of fat and muscle tissue when cells cannot utilize glucose for energy despite its abundance in the bloodstream 2

Metabolic Symptoms

• Polyphagia (increased hunger) paradoxically occurs despite elevated blood glucose because cells signal energy deficiency when insulin deficiency prevents glucose uptake—creating "starvation in the midst of plenty" 1, 2
• Blurred vision develops from osmotic lens swelling as elevated glucose accumulates in the lens, drawing water in and altering its refractive properties 3

Secondary and Associated Symptoms

Gastrointestinal Manifestations

• Nausea can occur directly from high blood glucose levels, especially when levels remain elevated for extended periods 4
• Hyperglycemia increases perception of gastrointestinal symptoms including abdominal pain 4
• These symptoms may signal progression toward diabetic ketoacidosis if accompanied by vomiting 4, 5

Other Common Symptoms

• Fatigue and drowsiness develop as cells cannot efficiently utilize glucose for energy 1, 5
• Increased susceptibility to infections occurs due to impaired polymorphonuclear leukocyte mobilization, chemotaxis, and phagocytic activity 6

Critical Warning Signs of Severe Hyperglycemia

Diabetic Ketoacidosis (DKA) Symptoms

When hyperglycemia progresses to DKA, symptoms include fruity breath odor, deep rapid breathing (Kussmaul respirations), nausea, vomiting, abdominal pain, altered mental status progressing to confusion or coma, and severe dehydration. 1, 5, 7

• DKA symptoms typically develop gradually over hours to days 5
• The fruity breath odor results from acetone, a ketone body 5
• Heavy breathing and rapid pulse indicate more severe metabolic derangement 5

Hyperosmolar Hyperglycemic State (HHS)

• HHS presents with severe hyperglycemia (often >600 mg/dL), profound dehydration, and altered mental status without significant ketoacidosis 1
• This condition has a slower onset than DKA but more severe dehydration 8
• More commonly seen in type 2 diabetes 1

Important Clinical Considerations

Asymptomatic Hyperglycemia

• Type 2 diabetes frequently remains undiagnosed for years because hyperglycemia develops gradually and early stages may not be severe enough to produce noticeable symptoms 1
• Even asymptomatic patients with undiagnosed diabetes face increased risk of macrovascular and microvascular complications 1

Age-Related Variations

• Elderly patients are less likely to experience typical polyuria and polydipsia because renal threshold for glycosuria increases with age and thirst mechanisms become impaired 2

Acute vs. Chronic Presentation

• In previously undiagnosed diabetes, classic symptoms (polyuria, polydipsia, weight loss) typically occur for several days to weeks before diagnosis 3
• Acute severe hyperglycemia from stress or illness can cause symptoms even in patients with previously well-controlled diabetes 1

Critical Action Points

Any patient presenting with symptoms of marked hyperglycemia accompanied by nausea, vomiting, altered mental status, or signs of dehydration requires immediate evaluation for DKA or HHS, both of which are life-threatening emergencies. 1, 4, 7

• Check blood or urine ketones immediately when hyperglycemia is accompanied by nausea and vomiting 4
• Random plasma glucose ≥200 mg/dL plus classic symptoms is sufficient to diagnose diabetes 3
• Do not assume all symptoms are from hyperglycemia alone—concurrent illness, infection, or other metabolic disorders must be excluded 2