warum kein kaffee vor blutabnahme — what are common causes?

The recommendation to avoid coffee before a blood draw is based on several medical reasons. Caffeine can stimulate stress hormones like cortisol and adrenaline, which may alter fasting blood test results (e.g., glucose, lipid profiles). Coffee also affects blood sugar levels and can transiently raise triglycerides. It may influence liver enzymes and electrolyte balance. Most laboratories advise fasting for 8–12 hours with only water allowed. The evidence comes from clinical practice and lab guidelines rather than single studies. For certain tests (e.g., caffeine metabolism), coffee may be intentionally consumed – always follow your doctor's specific instructions.