wie lange kein kaffee vor blutabnahme — what can you do yourself?

The question of how long to avoid coffee before a blood draw is rooted in well-established pre-analytical standards. Coffee – even black – can interfere with many lab values: it raises blood glucose (transiently), alters lipid profiles (increases free fatty acids), stimulates cortisol and adrenaline, and may affect liver enzymes (e.g., GGT) and electrolytes. The standard recommendation is 8–12 hours of strict fasting before blood collection, including coffee, tea, juices, and milk. Water is allowed. What you can do yourself: schedule the appointment early in the morning, drink only water beforehand, and adhere to the fasting period consistently. This is mandatory for tests like fasting glucose, lipid panel, or oral glucose tolerance test. For pure hormone or vitamin measurements, restrictions may vary by lab – ask if unsure. The evidence is based on decades of clinical practice and guidelines (e.g., from the German Society for Clinical Chemistry and Laboratory Medicine), not on single RCTs. Some studies show that even one cup of coffee can raise fasting glucose by 10–20 %. Therefore, when in doubt, skip coffee entirely until after the blood draw.