Glycemic Lab Tests

Fasting insulin is most useful when interpreted with fasting glucose rather than alone. HbA1c values above 5.5% warrant investigation, while pushing below 5.5% is not described as beneficial. Fasting glucose mainly reflects hepatic overnight glucose release and can miss peripheral insulin resistance. Standard glycemic tests are meaningfully affected by outside factors such as sleep, hydration, meals, exercise, stress, and concurrent conditions. Iron deficiency can falsely raise HbA1c and cause misclassification if HbA1c is used alone. HbA1c reflects average glucose exposure over about 90 days and is more stable than fasting glucose for trend tracking.