Fast or no fast? Here's what patients should know…

Fasting before a blood test isn’t always required, but for certain tests it can directly affect the accuracy of your results. Understanding when fasting is necessary and how to prepare properly helps ensure your results are reliable and avoids the need for repeat testing.

In this guide, we’ll walk you through when fasting is required, how long to fast, and what to expect before your appointment.

When is fasting required?

Some blood tests require fasting because food and drink can temporarily change the levels of certain substances in your blood.

Common tests that may require fasting include:

• Blood glucose (sugar) tests

• Cholesterol and lipid panels

• Certain metabolic panels

If your test requires fasting, your healthcare provider or our team will let you know in advance.

How long should you fast?

In most cases, fasting means not eating or drinking anything except water for 8 to 12 hours before your test.

For example, if your appointment is in the morning, you may be asked to stop eating the night before.

Always follow the specific instructions provided, as fasting times can vary depending on the test.

What can you have while fasting?

During a fasting period, you can typically:

• Drink water

• Take medications if approved by your doctor

You should avoid:

• Food of any kind

• Coffee, tea, or juice

• Sugary or flavored drinks

Even small amounts can affect your results, so it’s best to follow guidance closely.

What happens if you don’t fast?

If you eat or drink something when fasting is required, your test results may be inaccurate.

In some cases, this could mean:

• Needing to repeat the test

• Delays in diagnosis or treatment

If you’re unsure whether you’ve followed the instructions correctly, it’s always best to let us know before your appointment.

Do all blood tests require fasting?

No. Many common blood tests do not require fasting.

In fact, most routine tests can be completed without any preparation at all. Fasting is only required for specific types of testing, so it’s important not to assume either way.

If you’re unsure, our team can confirm this for you before your visit.

Preparing for your appointment

To make your appointment as smooth as possible:

• Confirm whether fasting is required

• Stay hydrated by drinking water

• Have your ID and any necessary paperwork ready

• Choose a time that works best for your schedule

With Blood Script, you can book your appointment at home, at work, or at your care facility, making the process simple and convenient.

A faster, more convenient way to get tested

Blood Script brings professional lab testing directly to you, eliminating the need to travel or wait in line.

With same-day appointments and results available in as little as 4 hours for many tests, we make it easier to get the answers you need, quickly and reliably.

Ready to book your lab draw?

If you need a blood test and want a faster, more convenient experience, you can book your appointment in minutes.

We’ll handle everything from collection to delivery so you can focus on what matters most.