Evidence check: HbA1c in the context of Müdigkeit

HbA1c (glycated hemoglobin) is a well-established biomarker reflecting average blood glucose over the preceding 2–3 months. Elevated HbA1c indicates impaired glucose tolerance or diabetes, both of which can cause fatigue, especially when poorly controlled. However, fatigue is a highly non-specific symptom. Many other factors—sleep deprivation, stress, iron deficiency, thyroid dysfunction, vitamin D deficiency—are equally or more common causes. A normal HbA1c does not rule out metabolic contributors, as large glucose swings (e.g., reactive hypoglycemia) can also induce fatigue. The evidence linking HbA1c specifically to fatigue is indirect: strong for diabetes-related fatigue, but no direct validation of HbA1c as a standalone fatigue marker. For persistent fatigue, a medical workup including fasting glucose, oral glucose tolerance test, and other labs is warranted. The NutriCare DNA test from the context analyzes genetic variants that may influence metabolism, but it does not measure HbA1c. Interpretation of HbA1c values should be done by a clinician. Evidence level: human-moderate (HbA1c as diabetes marker is strong, but for fatigue specifically it is indirect).