warum kein kaffee vor blutabnahme — what can you do yourself?

Coffee before a blood draw can skew many lab results. Caffeine triggers the release of stress hormones like cortisol and adrenaline, which transiently affect blood glucose and lipid metabolism. Even black coffee without milk or sugar can raise triglyceride and cholesterol levels because caffeine stimulates lipolysis. Fasting glucose may also increase, potentially leading to misinterpretation, especially if diabetes is suspected. Additionally, coffee has a diuretic effect, altering fluid balance and making veins harder to access. What can you do yourself? Stick to the recommended fasting period of 8–12 hours — that means no coffee, tea, or other beverages except plain water. Drink enough still water beforehand to stay hydrated and improve vein visibility. Also avoid smoking and chewing gum. If you take medications, ask your doctor beforehand whether to take them as usual. The evidence is based on clinical practice and laboratory guidelines, not on large randomized trials. Individual sensitivity varies, but to be safe: no coffee before routine blood tests.