Some blood tests need special preparation and others don’t. So the answer to “Do I need to fast?” depends on what has been requested. The most useful step is to get clear instructions from the doctor and the laboratory before you go.

Check the exact list of tests

Write down which tests have been requested and why. Ask whether they need to be done at a particular time, whether fasting is needed and for how long. Don’t automatically carry over the preparation from a previous visit to a new request.

The NHS states that the health professional should explain the preparation needed. It may include fasting for certain tests or special instructions about medicines. The conditions depend on the test; the general rule “always without food and water” is not a suitable universal instruction.

What to check about food and drink

If fasting has been requested, ask exactly what is allowed and until when. In the East Kent Hospitals patient instructions for fasting tests, water is allowed but other drinks are restricted. Use the specific instructions of the laboratory that will process your samples.

If you have diabetes or a condition in which fasting may require a special plan, discuss the preparation with your doctor in advance. Don’t go without food for a long period on your own based on advice from a general internet article.

Don’t change your medicines on your own

Tell the doctor and the laboratory which medicines and supplements you take. If there are special instructions about the time you take them or a temporary change, they should be explained to you individually. East Kent Hospitals explicitly advises not to change your medication without a doctor’s instructions.

Ask what to do if you usually take a medicine with food. Don’t skip a dose just because someone else was given such instructions for a different test.

A short list before the visit

  • The exact names of the requested tests and the documents needed.
  • The instructions for preparation, food, drinks and the time the sample is taken.
  • Confirmation of the laboratory’s arrangements and opening hours.
  • Information about medicines, supplements and relevant particular circumstances.
  • How you will receive the results and discuss them with the doctor.

If you have not followed an instruction, say so before the sample is taken. The laboratory or the doctor will decide whether the test can go ahead or needs to be rescheduled.

Plan the conversation after the results

A number outside the reference range does not by itself give a full diagnosis. Discuss the results with the doctor who requested them, together with your symptoms and previous tests. Don’t keep ordering new panels based only on automatic explanations of a result.

If you are looking for a GP to discuss your results with, see Dr Boris Gavrilov’s profile and the practice’s website. trqbvami.com has an editorial partnership with Dr Boris Gavrilov’s practice.