wie lange vor blutabnahme nichts essen — can a microbiome test help?

The question mixes two different test types: fasting rules apply to blood tests (e.g., glucose, lipids), not to microbiome tests. A microbiome test (stool sample) does not require fasting. Whether such a test can help with digestive issues is scientifically debated. The evidence for personalized recommendations from microbiome data is weak and often marketing-driven. Results are highly variable day-to-day and not diagnostic. It is more useful to consult a doctor for established stool tests (e.g., for inflammatory markers or pathogens). A microbiome test may serve as supplementary information but does not replace medical diagnostics. Caveat: caution is advised for children or immunocompromised individuals.