From the Guidelines
Testing for hypoglycemia and glucose dysregulation should involve blood glucose monitoring, with hypoglycemia defined as a blood glucose level below 70 mg/dL, and specialized tests such as oral glucose tolerance test (OGTT) and hemoglobin A1C testing to identify patterns and causes, as recommended by the most recent guidelines 1.
Key Recommendations
- For suspected hypoglycemia, patients should use a home glucose meter to check levels during symptomatic episodes, documenting readings, symptoms, and timing relative to meals and medications.
- A continuous glucose monitor (CGM) may provide more comprehensive data by tracking glucose levels throughout the day and night.
- For formal diagnosis, a supervised 72-hour fast in a medical setting may be necessary, with blood samples taken when symptoms appear or glucose levels drop below 60 mg/dL.
- Additional testing includes measuring insulin, C-peptide, and proinsulin levels during hypoglycemic episodes to determine if excess insulin production is occurring.
Diagnostic Criteria
- Hypoglycemia is defined as a blood glucose level below 70 mg/dL, with level 1 hypoglycemia defined as a measurable glucose concentration <70 mg/dL but ≥54 mg/dL, level 2 hypoglycemia defined as a blood glucose concentration <54 mg/dL, and level 3 hypoglycemia defined as a severe episode requiring assistance from another person 1.
- The diagnosis of diabetes can be made using fasting plasma glucose, oral glucose tolerance test, or hemoglobin A1C testing, with a value >7.0 mmol/L (>126 mg/dL) diagnostic of diabetes 1.
Testing Procedures
- Oral glucose tolerance test (OGTT) can be performed by drinking a glucose solution and measuring blood glucose at intervals over 2-3 hours.
- Hemoglobin A1C testing provides information about average glucose levels over the previous 2-3 months.
- Blood glucose monitoring should be performed using a home glucose meter or a continuous glucose monitor (CGM), with results documented and reviewed regularly to identify patterns and causes of hypoglycemia or glucose dysregulation 1.
From the Research
Testing for Hypoglycemia and Glucose Dysregulation
To test for hypoglycemia and glucose dysregulation, several methods can be employed, including:
- Fasting plasma glucose (FPG) tests
- Oral glucose tolerance tests (OGTT)
- Glycosylated hemoglobin (HbA1c) tests
- Insulin sensitivity tests, such as the hyperinsulinemic euglycemic clamp
Oral Glucose Tolerance Test (OGTT)
The OGTT is a commonly used test to diagnose glucose dysregulation, including type 2 diabetes 2, 3, 4, 5. This test measures the body's ability to regulate blood glucose levels after consuming a sugary drink. The results of the OGTT can be used to diagnose:
- Normal glucose tolerance
- Impaired glucose tolerance
- Type 2 diabetes
Fasting Plasma Glucose (FPG) Test
The FPG test measures blood glucose levels after an overnight fast 2, 6, 4, 5. This test can be used to diagnose:
- Normal fasting glucose
- Impaired fasting glucose
- Type 2 diabetes
Limitations of FPG Test
However, the FPG test has limitations, as it may not detect all cases of glucose dysregulation 6, 5. For example, some individuals with normal FPG levels may still have impaired glucose tolerance or type 2 diabetes.
Importance of OGTT
The OGTT is a more sensitive test for detecting glucose dysregulation, particularly in individuals with normal FPG levels 2, 3, 4, 5. The OGTT can detect impaired glucose tolerance and type 2 diabetes, even in individuals with normal FPG levels.
Diagnostic Agreement between FPG and OGTT
The diagnostic agreement between FPG and OGTT is limited, with a kappa value of 0.55 5. This means that relying solely on FPG levels may not be adequate for diagnosing glucose dysregulation, and OGTT should be considered as a complementary test.
Clinical Implications
The results of these studies have important clinical implications for the diagnosis and management of glucose dysregulation 2, 6, 3, 4, 5. Healthcare providers should consider using OGTT in addition to FPG tests to diagnose and monitor glucose dysregulation, particularly in high-risk individuals.