Nüchtern means you come to the blood draw on an empty stomach, which in practice means no food for around 8 to 12 hours before the appointment.
Water, coffee and juice are treated differently before the draw:
- Water with nothing in it is fine and even helpful, because it makes the blood draw easier.
- Coffee with milk or sugar counts as food, so it breaks the fast.
- Juice and a normal breakfast both count as food as well.
Fasting matters because some values change after eating, so blood sugar rises after every meal and blood fats like triglycerides can stay raised for hours. Measured shortly after breakfast, those values describe your breakfast more than your body. The values in a großes Blutbild are barely affected by food, so a blood count alone does not need fasting.
Whether you need to come nüchtern depends on which values your doctor ordered, so the honest answer is always to ask the practice when you book. Morning appointments make fasting easiest, since most of the fasting hours happen while you sleep.
If you take regular medicines, do not simply skip them, and ask the practice beforehand whether to take them as usual or after the blood draw.
This glossary entry is general information, not medical advice, and it is not intended to diagnose, treat or rule out any condition. Discuss your own results with a clinician who knows your history.
