From the Guidelines
Diagnosing hypoglycemia involves measuring blood glucose levels, with a threshold of <70 mg/dL (3.9 mmol/L) confirming the condition, and classifying it into levels based on severity, as outlined in the 2023 standards of care in diabetes 1. To diagnose hypoglycemia, the following steps can be taken:
- Measure blood glucose levels when symptoms occur, using a home glucose meter or laboratory testing, with levels below 70 mg/dL (3.9 mmol/L) confirming the condition 1.
- Classify hypoglycemia into levels based on severity, with level 1 defined as a glucose concentration <70 mg/dL (3.9 mmol/L) but ≥54 mg/dL (3.0 mmol/L), level 2 defined as a glucose concentration <54 mg/dL (3.0 mmol/L), and level 3 defined as a severe event characterized by altered mental and/or physical status requiring assistance for treatment of hypoglycemia 1.
- Use Whipple's triad to confirm the diagnosis: documented low blood glucose, presence of typical symptoms, and resolution of symptoms after glucose levels are restored.
- For suspected hypoglycemia, patients should check blood glucose during symptoms, and fasting tests may be necessary to diagnose recurring hypoglycemia, typically conducted in a medical setting where blood glucose is monitored after an overnight fast for up to 72 hours.
- Additional workup may include insulin, C-peptide, and sulfonylurea levels to determine the cause, and providers should counsel patients to treat hypoglycemia with fast-acting carbohydrates at the hypoglycemia alert value of 70 mg/dL (3.9 mmol/L) or less 1. The most recent and highest quality study, published in 2023, provides the basis for these recommendations, emphasizing the importance of prompt diagnosis and treatment to prevent neurological damage and identify underlying causes 1.
From the Research
Diagnosis of Hypoglycemia
To diagnose hypoglycemia, the following steps can be taken:
- Identify symptoms consistent with hypoglycemia, such as adrenergic or neuroglycopenic symptoms 2
- Measure plasma glucose concentration, with hypoglycemia defined as a level under 70 mg/dL (3.9 mmol/L) 3 or 50 mg per dl or less 2
- Document Whipple's triad, which includes symptoms, signs, or both consistent with hypoglycemia, a low plasma glucose concentration, and resolution of those symptoms or signs after the plasma glucose concentration is raised 4, 5
- Pursue clinical clues to potential hypoglycemic etiologies, such as drugs, critical illnesses, hormone deficiencies, or nonislet cell tumors 4
- Consider a 72-h supervised fast test with measurement of plasma insulin, c-peptide, pro-insulin, and beta-hydroxybutyrate levels, coupled with plasma/urine sulphonylurea screen, for diagnostic evaluation 5
Laboratory Tests
Laboratory tests that can be used to diagnose hypoglycemia include:
- Measurement of glucose, insulin, C-peptide, and other related compounds 2
- Plasma glucose concentration measurement 3, 2
- Insulin and C-peptide measurement during an episode of hypoglycemia 4
- Beta-hydroxybutyrate measurement 5
- Sulphonylurea screen 5
Special Considerations
Special considerations for diagnosing hypoglycemia include:
- Patients with diabetes mellitus, who are at increased risk of hypoglycemia 3, 4
- Patients with impaired hypoglycemia awareness, who may not exhibit typical symptoms of hypoglycemia 3
- Patients with a history of severe hypoglycemia, who may require more frequent monitoring and treatment 3
- Patients who are fasting for laboratory tests, who may be at risk of hypoglycemia 6