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 due to osmotic effects of elevated blood glucose and cellular energy deficiency despite abundant circulating glucose. 1

Primary Symptoms

Osmotic Symptoms

• Polyuria develops when blood glucose exceeds the renal threshold (typically ~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 losses from osmotic diuresis 1
• Dehydration results from the combination of excessive urination and inadequate fluid replacement 1

Metabolic Symptoms

• Unintentional weight loss occurs because cells cannot utilize glucose without adequate insulin, forcing the body to break down fat stores through unregulated lipolysis and muscle protein for alternative energy 2
• Polyphagia (increased hunger) paradoxically accompanies weight loss because cells signal energy deficiency even though blood glucose is elevated—creating "starvation in the midst of plenty" 2

Visual Symptoms

• Blurred vision results from osmotic lens swelling, where elevated blood glucose accumulates in the lens and draws water in through osmotic pressure, altering its refractive properties 3
• This is distinct from diabetic retinopathy and is acutely reversible with glycemic control 3

Secondary and Warning Symptoms

Gastrointestinal Manifestations

• Nausea can occur directly from high blood glucose levels, especially when levels remain elevated for extended periods 4
• Hyperglycemia substantially slows gastric emptying and increases perception of gastrointestinal symptoms including abdominal pain 4

Neurological Symptoms

• Fatigue and weakness develop from cellular energy deficiency 3
• Difficulty concentrating may occur with moderate hyperglycemia 5

Severe Hyperglycemia Warning Signs

Diabetic Ketoacidosis (DKA) Symptoms

When hyperglycemia progresses to DKA, symptoms include drowsy feeling, flushed face, fruity odor on breath, nausea, vomiting, stomach pain, heavy breathing, and rapid pulse—this is a life-threatening emergency requiring immediate medical care. 5, 1

• DKA symptoms typically develop gradually over hours to days 5
• Blood and urine tests show large amounts of glucose and ketones 5
• If uncorrected, DKA can lead to dehydration, loss of consciousness, or death 5

Hyperosmolar Hyperglycemic State (HHS)

• HHS is characterized by severe hyperglycemia, hyperosmolality, and dehydration in the absence of significant ketoacidosis 1
• More common in type 2 diabetes and can present with or without prior diabetes diagnosis 1

Important Clinical Considerations

Asymptomatic Hyperglycemia

• Type 2 diabetes frequently goes undiagnosed for years because hyperglycemia develops gradually and at earlier stages is often not severe enough to cause noticeable symptoms 1
• Even asymptomatic patients with undiagnosed diabetes are at increased risk for macrovascular and microvascular complications 1

Population-Specific Variations

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

Critical Action Points

• Check blood glucose immediately when classic symptoms are present, as random plasma glucose ≥200 mg/dL plus symptoms is sufficient to diagnose diabetes 3
• Check blood or urine ketones immediately if nausea and vomiting accompany hyperglycemia, as this may indicate DKA 4
• Patients taking SGLT2 inhibitors should stop medication and seek immediate medical attention if they develop dyspnea, nausea, vomiting, or abdominal pain due to increased risk of euglycemic DKA 4