Preparing for blood tests: food, medicines and the questions to clarify

Clarify what is being tested and why

Ask for the test name, specimen type and how the result will inform your care. A specimen collected outside the laboratory may have particular transport requirements. Request written instructions when they are complex. A general phrase such as “blood check” does not define the preparation needed for every test.

What laboratory fasting means

When fasting is requested, it generally means plain water only and no food; coffee is not a substitute for water. The period is often 8–12 hours, but the test instructions determine the exact duration. Smoking, chewing gum and exercise are also avoided during the fast. Do not automatically fast when you have not been asked to.

Medicines should not be stopped by a blanket rule

Report the medicines, vitamins and supplements you take. Some tests have particular instructions, but do not stop a medicine without advice from your healthcare professional. If you did not follow the preparation, say so before testing. The aim is to make the right decision about the sample, not to conceal a meal or a dose taken.

Why biotin should also be mentioned

Biotin is present in some supplements and can interfere with certain laboratory methods. Among other concerns, the FDA has reported falsely low troponin results due to this interference. This does not mean every test is affected. Report the product and dose; do not treat an online stopping interval as a rule for all tests.

Plan your morning around the instructions

If a test does not require fasting, there is no reason to treat it as a fasting test. When fasting is needed, an early blood draw can make the morning easier to organise. You can bring something to eat after collection is complete. This addresses practical planning; it does not replace individual instructions about medicines or food.

Concern about needles can be discussed too

If you feel anxious, ask what the procedure involves. Looking away or talking with the staff may help. Tell them immediately if you feel dizzy or nauseated during sample collection. You do not have to silently endure a concern that the team can take into account.

In practice, at Anna Maria Lab

Patients can walk in Monday–Saturday, 07:00–18:00; samples are collected during the same hours. This does not remove test-specific preparation requirements. A useful question before visiting is: “I have this test list. Which tests need preparation, and do any require a particular collection time?” Result turnaround depends on the test.

Keep a short note of the instructions received, your planned time and any points to clarify. Do not replace the test list with the approximate name of a package you remember. Clarity at this stage makes communication easier.