What are the signs and symptoms of hyperglycemia?

Signs and Symptoms of Elevated Blood Sugars

The most common symptoms of hyperglycemia are increased thirst (polydipsia), frequent urination (polyuria), and blurred vision, which occur when blood glucose levels exceed the renal threshold of approximately 180 mg/dL. 1

Classic Symptoms of Hyperglycemia

Hyperglycemia typically presents with a constellation of symptoms that develop gradually over hours or days:

Early/Common Symptoms:

• Polydipsia (increased thirst)
• Polyuria (frequent urination)
• Blurred vision
• Fatigue/weakness
• Dry mouth
• Not feeling right
• Sweet or funny taste in mouth 2

Advanced Symptoms:

• Weight loss (unintentional)
• Increased hunger
• Headache
• Difficulty concentrating
• Nausea
• Drowsiness 3

Symptom Classification

Research has identified four main symptom groupings of hyperglycemia 2:

1. Osmotic symptoms: Thirst, dry mouth, frequent urination, weakness, not feeling right, sweet/funny taste
2. Agitation symptoms: Feeling tense, irritability, restlessness, poor concentration
3. Neurological symptoms: Dizziness, blurred vision, light-headedness, weakness
4. Malaise symptoms: Headache, nausea

Severe Hyperglycemia and Diabetic Ketoacidosis (DKA)

If hyperglycemia remains untreated over several days, it can progress to diabetic ketoacidosis (DKA), especially in people with Type 1 diabetes. Signs and symptoms of DKA include:

• Nausea and vomiting
• Abdominal pain
• Fruity smell on breath (acetone breath)
• High levels of ketones in blood and urine
• Dehydration
• Rapid breathing (Kussmaul respiration)
• Confusion
• Loss of consciousness (in severe cases) 1, 3

For patients using insulin pumps, lack of insulin supply may lead to DKA more rapidly than in other patients 1.

Factors Affecting Hyperglycemia Symptoms

Several factors influence how patients experience hyperglycemia:

• Age: Younger people tend to experience more intense symptoms 2
• Duration of diabetes: Symptom awareness may change over time
• Individual variation: The blood glucose threshold at which symptoms appear varies (median 15 mmol/L or 270 mg/dL, but ranges from 8-30 mmol/L or 144-540 mg/dL) 2
• Comorbid conditions: Stress, illness, or infections can exacerbate hyperglycemia 4

Clinical Implications

Chronic hyperglycemia can lead to both acute complications and long-term damage:

• Acute effects: Osmotic diuresis, dehydration, electrolyte imbalances
• Long-term complications: Retinopathy, nephropathy, neuropathy, cardiovascular disease 5

Even brief periods of hyperglycemia can increase the risk of complications, highlighting the importance of early recognition and treatment 6.

Common Pitfalls in Recognizing Hyperglycemia

• Symptoms may be subtle or attributed to other causes, especially in elderly patients
• Some patients (particularly those with long-standing diabetes) may have reduced awareness of hyperglycemic symptoms
• Hyperglycemia can be present without obvious symptoms until blood glucose levels are significantly elevated
• Symptoms may overlap with other conditions, leading to delayed diagnosis

Early recognition of hyperglycemic symptoms is crucial for prompt intervention to prevent progression to more severe metabolic derangements and reduce the risk of long-term complications.