Nüchternheit

Nüchternheit describes a defined period without food before a blood sample is taken, in practice usually 8 to 12 hours. Water is permitted and normally encouraged, because a well-hydrated vein is easier to work with.

It is not required for everything, and treating it as a blanket rule costs appointments:

• Nüchternglukose requires Nüchternheit as part of its own definition.
• Triglycerides are strongly affected by a meal eaten shortly before the draw.
• HbA1c reflects blood sugar over a much longer period and does not require it.

Which analyses in a given panel need it is set by the akkreditiertes Labor that will run them, and its Präanalytik handbook states this per analysis. A pharmacy should follow that handbook rather than general fasting advice.

What still counts as nüchtern is the part customers ask about:

• Water is fine before the appointment and while waiting for the draw.
• Coffee, tea with milk, juice, sweets and chewing gum are not permitted.
• Medicines are usually continued unless a physician has said otherwise, which is a decision for the physician rather than the pharmacy.

The practical consequence is scheduling, because a panel that requires Nüchternheit belongs in the first appointments of the morning, which also concentrates the venöse Blutentnahme workload into a predictable window.

When the requirement was not met, the sample is not automatically wasted. Recording that the person was not nüchtern on the request form lets the laboratory mark the affected values rather than report them without context, and it protects the Referenzbereich comparison from being read as more meaningful than it is. Documenting the fasting status is part of ordinary Präanalytik discipline.