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

The question 'How long should I fast before a blood draw?' refers to the recommended fasting period before blood collection to obtain reliable laboratory results. In standard clinical practice, a fasting period of 8–12 hours is typical, during which only water (without sugar, caffeine, or milk) is allowed. This is especially important for blood glucose, lipids (triglycerides, cholesterol), and certain hormones that fluctuate significantly after food intake. Short fasting (< 8 h) can skew fasting glucose or LDL cholesterol values. Prolonged fasting (> 12 h) may shift metabolism into a starvation state, elevating ketones or free fatty acids. For some tests (e.g., HbA1c, PSA, thyroid function), strict fasting is not mandatory, but many laboratories still recommend it for standardization. Importantly, specific instructions should always be confirmed with the ordering physician or lab, as requirements vary by test. For genetic or nutrigenetic tests (like those from MyBody‑X), fasting is usually unnecessary because DNA is stable. However, if the blood draw is also used for biomarker analysis (e.g., glucose, lipids), fasting may be required. The evidence for these guidelines is strong clinical practice, not a single study. Safety note: Patients on medications or with chronic conditions (e.g., diabetes) should discuss fasting duration with their doctor to avoid hypoglycemia.