How to Diagnose Hypoglycemia

Many women experience dizziness and visual darkening (e.g., blacking out or tunnel vision) in daily life. Most assume this is due to hypoglycemia, but it’s advisable to consult a healthcare provider for proper evaluation. So, how is hypoglycemia diagnosed?

How Is Hypoglycemia Diagnosed?

There are two primary methods for detecting hypoglycemia: self-monitoring using a blood glucose meter and clinical testing performed at a hospital. In healthy individuals, a blood glucose level below 2.8 mmol/L (or <50 mg/dL) suggests possible hypoglycemia. However, to confirm a diagnosis of hypoglycemia, the underlying cause must be identified.

Patients may perform a supervised fasting test themselves—for example, finishing their last meal at 6–7 a.m. and then abstaining from all caloric intake until the following morning at 6–7 a.m., resulting in a 12-hour fast to assess whether hypoglycemic episodes occur. If no symptoms develop, the fasting period may be extended further—e.g., to noon the next day (i.e., a 16-hour fast).

If no hypoglycemia occurs after 16 hours of fasting, hypoglycemia is unlikely. Some hospitals may extend the fasting test to 20 hours to increase sensitivity for detecting hypoglycemia. If hypoglycemia does occur during fasting, simultaneous measurements of blood glucose and insulin levels should be obtained, and the insulin-to-glucose ratio (also known as the insulin secretion index) should be calculated to determine whether insulin secretion is abnormal. If the index is normal, an insulinoma (insulin-secreting pancreatic neuroendocrine tumor) should be considered.

The most common initial symptom of hypoglycemia is dizziness, accompanied by visual darkening (e.g., “blacking out”) or headache. Additional symptoms may include nausea and palpitations. If these symptoms occur, prompt medical evaluation is recommended. We hope this information has been helpful!