wie viel wasser vor blutabnahme — which blood markers matter?

The question of how much water to drink before a blood draw depends on which markers are being measured. General medical practice: for most routine tests (complete blood count, liver/kidney function, thyroid hormones), moderate water intake (1–2 glasses) is allowed and even recommended to improve vein access. However, certain markers are sensitive to hydration status: aldosterone, renin, cortisol, and antidiuretic hormone (ADH) can be significantly altered by water intake. Electrolytes like sodium and potassium may be diluted by excessive water. For fasting glucose or oral glucose tolerance tests, strict fasting (no water) is required. For consumer tests like MyBody-X hormone panels, the instructions typically allow water, but the evidence is based on practice rather than strong clinical trials. Caveat: If you are unsure about specific markers (e.g., aldosterone/renin ratio), consult a physician. The key is to follow the test kit instructions and avoid extreme water intake (more than 500 ml) shortly before the draw.