Signs and Symptoms of Hypoglycemia
Hypoglycemia presents with two distinct categories of symptoms: autonomic (sympathetic) symptoms from counterregulatory responses and neuroglucopenic symptoms from brain glucose deprivation, with shakiness, sweating, irritability, confusion, tachycardia, and hunger being the most common manifestations. 1
Autonomic (Sympathetic) Symptoms
These arise from the body's counterregulatory response and typically appear first:
- Shakiness/tremor - one of the most frequently reported symptoms 1, 2
- Sweating - occurs in approximately 26-27% of severe hypoglycemic episodes 2
- Tachycardia (rapid heartbeat) 1, 3
- Hunger 1
- Anxiety or irritability 1, 3
- Tingling of lips and tongue 3
- Palpitations 4
Neuroglucopenic Symptoms
These result from inadequate glucose delivery to the brain and indicate more severe hypoglycemia:
- Confusion or disorientation - reported in 22-37% of severe episodes 1, 2
- Weakness/fatigue - the most frequently reported symptom (29-30% of cases) 2
- Difficulty concentrating 3
- Dizziness or lightheadedness 3, 4
- Blurred vision or other vision changes 3, 4
- Slurred speech 3
- Headache 3, 4
- Drowsiness or somnolence 3, 5
Severe Hypoglycemia (Level 3) Manifestations
When blood glucose drops critically low (<54 mg/dL or symptoms progress):
- Loss of consciousness - occurs in approximately 25% of severe episodes 2
- Seizures or convulsions 3, 4
- Altered mental status requiring assistance from another person 1
- Inability to self-treat 1
Critical Cardiovascular Manifestation
- Marked sinus bradycardia - can occur with severe hypoglycemia, particularly dangerous as it represents a reversible cause of symptomatic bradycardia 6
- QT prolongation 6
Important Clinical Pitfalls
Beta-adrenergic blockade can mask early autonomic warning symptoms (especially tachycardia), making recognition of hypoglycemia more difficult and potentially allowing progression to severe neuroglucopenic symptoms without adequate warning. 6
Impaired hypoglycemia awareness is a dangerous condition where early warning symptoms become blunted or absent, particularly after recurrent hypoglycemic episodes, allowing blood glucose to drop to dangerously low levels before symptoms are recognized. 1 This occurs more commonly with:
- Long duration of diabetes 1
- Diabetic neuropathy 1
- Intensified diabetes control 1
- Recent episodes of level 2 or 3 hypoglycemia 1
Symptom Threshold Recognition
The blood glucose threshold of 70 mg/dL (3.9 mmol/L) triggers neuroendocrine counterregulatory responses in people without diabetes and should prompt immediate treatment, even before severe symptoms develop. 1 Waiting for more severe symptoms risks progression to level 2 (<54 mg/dL) or level 3 hypoglycemia with serious consequences including hospitalization (18-24% of severe episodes) 2.