wie lange kein kaffee vor blutabnahme — which blood markers matter?

The question of how long to avoid coffee before a blood draw depends on which markers are being measured. For routine blood counts (e.g., CBC, electrolytes, kidney function), black coffee in moderation is often acceptable if taken without milk, sugar, or cream. However, several markers are acutely affected by caffeine and other coffee compounds: - **Fasting glucose:** Coffee can transiently raise or lower blood sugar. For a reliable fasting glucose measurement, an 8–12 hour abstinence is standard. - **Triglycerides and LDL cholesterol:** Coffee, especially unfiltered, can alter lipid levels. A 12-hour fast from all food and coffee is recommended for accurate lipid profiles. - **Cortisol:** Caffeine stimulates adrenal glands, increasing cortisol. If stress hormones are being measured, coffee should be avoided for at least 2–3 hours beforehand. - **Homocysteine:** Some evidence suggests coffee can acutely raise homocysteine, which may affect interpretation of cardiovascular risk markers. Evidence is strong (human-strong) for glucose and triglycerides, and moderate (human-moderate) for cortisol and homocysteine. Important: For specific tests like an oral glucose tolerance test, absolute fasting is mandatory. When in doubt, stick to water for 8–12 hours before blood draw. Individual genetics (e.g., CYP1A2 variants) can influence caffeine metabolism, but general guidelines apply to most people.