warum kein kaffee vor blutabnahme — can a DNA test help?

The recommendation to avoid coffee before a blood draw is based on the fact that caffeine and other coffee compounds can cause acute metabolic and circulatory changes. Caffeine can temporarily raise blood pressure, increase heart rate, and stimulate the release of stress hormones like cortisol and adrenaline. It can also alter blood glucose levels and affect lab values such as triglycerides and liver enzymes. A DNA test cannot predict or replace these acute effects. However, it can identify genetic variants that influence caffeine metabolism, such as in the CYP1A2 gene. Slow caffeine metabolizers may have a higher risk of cardiovascular effects from coffee. Nevertheless, the standard advice remains: fast and avoid coffee before a blood draw to ensure reproducible and comparable lab results. A DNA test provides no acute guidance for the blood draw day, but rather long-term insights into individual caffeine tolerance. The evidence for the fasting recommendation is clinically strong, while DNA-based caffeine advice is based on mechanistic and population studies. Caution: Do not alter blood draw preparation without consulting a physician.