Interactive checklist

Blood test prep

Preparing correctly makes a result reliable the first time. Choose your test type for a prep checklist you can tick off, with the steps that matter most flagged. It saves on your device, so you can come back to it before your appointment.

Which test are you preparing for?

Some glucose and cholesterol tests are affected by recent food, so many labs ask you to fast beforehand.

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Fast for the time your lab specifies, commonly 8 to 12 hours Do not skipOnly if your request says fasting. Not all lipid tests need it now.
Keep drinking plain water so you stay hydrated and blood is easier to draw
Avoid food, sugary drinks, tea and coffee during the fasting windowBlack tea or coffee can still affect some results, so plain water is safest.
Ask your doctor whether to take your usual medicines that morning Do not skipDo not stop any prescribed medicine without advice.
Book a morning appointment so the fasting window is easier overnight
Avoid alcohol the day before, as it can affect glucose and lipids

Ticks are saved on this device only. Nothing is sent anywhere.

This is general guidance. Where it differs from the instructions on your test request or from your doctor or laboratory, follow theirs. Never stop a prescribed medicine to prepare for a test without medical advice.

Sources

Blood tests: how to prepare NHS, 2023

Last reviewed: 2026-07-16