wie lange vor blutabnahme nichts trinken — what does this mean exactly?

The instruction 'don't drink anything before a blood draw' typically means no caloric beverages (juice, coffee with milk, soda) for 8–12 hours prior. Plain water is often allowed and can even help with vein visibility. However, some specific tests (e.g., fasting glucose, lipid panel) may require complete abstinence from all fluids. The exact rule depends on your doctor's or lab's protocol. Dehydration can affect certain lab values (e.g., creatinine, electrolytes) and make venipuncture harder. MyBody-X tests (DNA, microbiome) generally do not require fasting, but for standard blood work, follow the lab's instructions. If in doubt, ask your healthcare provider. Evidence: common medical practice; no specific source in provided context.