wie lange nichts essen vor blutabnahme — which blood markers matter?

The required fasting duration before a blood draw depends on the markers being measured. For routine blood tests such as fasting glucose, triglycerides, and LDL cholesterol, a fasting period of 8–12 hours is standard because food intake can transiently alter these values. Triglycerides in particular rise sharply after a meal and may take up to 12 hours to return to baseline. Glucose is also affected, so strict fasting is necessary for diabetes screening or oral glucose tolerance tests. Other markers like HbA1c (long-term glucose), creatinine (kidney function), or liver enzymes (ALT, AST) are less influenced by recent food intake and can often be measured without fasting, though some labs still recommend fasting for consistency. Non-fasting samples can lead to false positives or negatives, especially for lipids and glucose. The evidence is based on clinical guidelines and is rated human-strong. Caveat: Always follow specific instructions from your doctor or lab; certain tests (e.g., oral glucose tolerance test) require strict fasting.