If you ate or drank something outside the fasting instructions, tell the laboratory before the sample is collected. Do not hide the mistake or try to undo it by extending the fast on your own.
Have these details ready
Write down the exact tests on the order, the appointment time, what you consumed, and approximately when. Include whether the instructions allowed plain water and whether another preparation step was missed. Report the facts without deciding which test must have been affected.
Use the facility's verified contact number or ask collection staff on arrival. A general customer-service answer may need to be referred to the ordering clinician or laboratory team.
Ask a question staff can answer
“My order includes these tests. I was instructed to fast, but I had this at this time. Should I attend as planned, and does the order need any change?”
This is a suggested call script, not a medical protocol. Staff may decide to proceed with documentation, collect only an authorized part of an order, or arrange another appointment. Do not cross out tests or assume the same answer applies to someone else's panel.
If the appointment changes
Confirm the new preparation instructions and whether the requisition remains valid. Ask how medicine timing should be handled if it is affected; do not skip a prescription independently. Record the new appointment and any fees or cancellation terms the service explains.
If you have diabetes, feel unwell while fasting, or have another condition that makes preparation difficult, contact the clinician for individualized advice. Do not prioritize preserving the appointment over addressing a health problem.
If the sample was already collected
Contact the ordering office or laboratory promptly and explain what happened. Ask whether the information should be added to the record and whether any follow-up is needed. Do not discard the report yourself or assume every result is invalid. Accurate context gives the team a better basis for deciding what the sample can answer.
Sources
- MedlinePlus: Fasting for a blood test
Fast only when instructed; preparation errors should be disclosed before collection.
- MedlinePlus: Preparing for a lab test
Preparation depends on the exact order; discuss medicines and supplements with the ordering professional.