What are the diagnostic criteria for hypoglycemia (low blood sugar)?

From the Guidelines

Hypoglycemia is diagnosed through a combination of symptoms, blood glucose measurements, and specialized testing, with a focus on identifying level 1, level 2, and level 3 hypoglycemia as defined by a measurable glucose concentration <70 mg/dL, <54 mg/dL, and a severe event characterized by altered mental and/or physical status requiring assistance for treatment, respectively 1. To diagnose hypoglycemia, healthcare providers first look for the presence of Whipple's triad: symptoms consistent with low blood sugar (such as shakiness, sweating, confusion, or palpitations), documented low blood glucose levels (typically below 70 mg/dL or 3.9 mmol/L), and resolution of symptoms after blood glucose is raised. Some key points to consider in the diagnosis of hypoglycemia include:

• Level 1 hypoglycemia is defined as a measurable glucose concentration <70 mg/dL (<3.9 mmol/L) and ≥54 mg/dL (≥3.0 mmol/L) 1
• Level 2 hypoglycemia is defined as a blood glucose concentration <54 mg/dL (<3.0 mmol/L) 1
• Level 3 hypoglycemia is defined as a severe event characterized by altered mental and/or physical status requiring assistance for treatment 1 For definitive diagnosis, blood tests should be performed during a hypoglycemic episode to measure glucose, insulin, C-peptide, and other hormones. Additional workup may include imaging studies to rule out insulinomas or other pancreatic tumors if spontaneous hypoglycemia is suspected. Early diagnosis is important as untreated hypoglycemia can lead to serious neurological complications, especially if episodes are frequent or severe. It is also important to note that the classification of hypoglycemia is outlined in Table 6.4, which provides a clear definition of level 1, level 2, and level 3 hypoglycemia 1. Healthcare providers should be aware of the symptoms of hypoglycemia, which include shakiness, irritability, confusion, tachycardia, sweating, and hunger, and should take immediate action to resolve the hypoglycemic event if level 2 or level 3 hypoglycemia is suspected 1.

From the Research

Diagnosis of Hypoglycemia

To diagnose hypoglycemia, the following steps can be taken:

• Measure the plasma glucose concentration, with hypoglycemia defined as a level of 50 mg per dl or less 2 or under 70 mg/dL (3.9 mmol/L) 3
• Identify symptoms, which can be classified as adrenergic or neuroglycopenic, and may include autonomic symptoms such as hunger, palpitations, tremor, sweating, and neuroglycopenic symptoms such as confusion, drowsiness, odd behavior, speech difficulties, and incoordination 2, 4
• Use diagnostic tests involving measurement of glucose, insulin, C-peptide, and other related compounds to identify the cause of hypoglycemia 2
• Consider continuous glucose monitoring (CGM) for individuals with increased risk for hypoglycaemia, impaired hypoglycaemia awareness, frequent nocturnal hypoglycaemia, and with history of severe hypoglycaemia 3

Classification of Hypoglycemia

Hypoglycemia can be classified as:

• Fasting hypoglycemia
• Reactive hypoglycemia
• Surreptitious hypoglycemia
• Artifactual hypoglycemia 2
• Severe hypoglycemia, defined as an episode requiring the assistance of another person to actively administer carbohydrate, glucagon, or take other corrective actions to assure neurologic recovery 3

Laboratory Tests

Laboratory tests can be used to diagnose and classify hypoglycemia, including:

• Measurement of plasma glucose concentration
• Measurement of insulin, C-peptide, and other related compounds
• Continuous glucose monitoring (CGM) 2, 3
• Blood glucose testing to identify hypoglycemic events, particularly in patients with diabetes who are fasting for laboratory blood tests 5