was essen vor blutabnahme — what are common causes?

The question about what to eat before a blood draw is important because many lab values are affected by food intake. For most routine blood tests (e.g., fasting glucose, lipid panel), a fasting period of 8–12 hours is recommended, during which only water is allowed. High-fat meals can skew triglycerides and liver enzymes, while carbohydrate-rich foods affect blood sugar and insulin levels. Caffeine, alcohol, and nicotine should also be avoided before the draw. For specific tests like the oral glucose tolerance test (OGTT), a standardized carbohydrate load is required. Common causes of abnormal results include non-fasting, medications, stress, infections, or circadian variations. Genetic factors (e.g., TCF7L2 variants for diabetes risk) can also play a role but are rarely decisive alone. Important: Always follow the instructions given by your doctor or lab. If unsure, consult before the blood draw.