Evidence check: Glukose in the context of fatigue

Glucose is the primary fuel for the brain and muscles. A drop in blood glucose (hypoglycemia) can cause fatigue, poor concentration, and irritability. Similarly, large blood sugar swings after high-sugar meals can lead to a reactive dip and subsequent exhaustion. However, the evidence for a direct causal link between glucose levels and fatigue in healthy individuals is mostly mechanistic and observational. No strong RCTs show that extra glucose intake reduces fatigue in non-diabetic people. In diabetes or prediabetes, cellular glucose deficiency (despite high blood sugar) can also contribute to fatigue. A blood glucose test (fasting or HbA1c) is advisable before using glucose as an 'energy booster'. Caution: excessive sugar intake is harmful long-term. Evidence: human-observational / mechanistic.