How to Prepare for a Fasting Blood Test

Getting a fasting blood test soon? You might be wondering how long you have to fast for a blood test, whether you have to avoid all food and drinks, and what happens if you accidentally eat something. Don’t worry, as it’s not as complicated as it sounds. Some blood tests require fasting to ensure accurate results, but our experts at Superdrug Clinics are here to explain everything. We’ll talk about why fasting is necessary and how to prepare properly for your appointment.

What Is a Fasting Blood Test?

A fasting blood test is exactly as it sounds: a blood test that requires you to fast (not eat or drink anything except water) for a specific amount of time beforehand, usually 8-10 hours for a Superdrug blood test, for other tests please check with your provider.

This is necessary for certain blood tests, as anything you’ve recently eaten or drunk can affect your levels of blood sugar, cholesterol, and other substances in the blood that may be measured to assess your health, known as biomarkers. Fasting before blood work ensures your results aren’t skewed by that latte or croissant you had for breakfast, so the doctors can get an accurate picture of your health.

If your doctor has asked you to fast before your test, don’t panic. It’s usually for a short window, and we have plenty of tips to make fasting easy.

We also suggest that you bring a snack or make sure you have access to some food after your appointment.

Why Does Fasting Affect Blood Test Results?

Everything you eat and drink ends up in the bloodstream, temporarily changing the levels of sugar, cholesterol, and other blood biomarkers. For example:

· Eating before a blood glucose test could raise your blood sugar and lead to higher readings, potentially giving a false impression of diabetes risk.

· Eating before a lipid panel could temporarily elevate cholesterol levels, making it harder to assess your actual cardiovascular health.

· Even certain drinks, like coffee or alcohol, may interfere with fasting blood test results by affecting hydration and liver enzyme levels.

Fasting ensures that your body has time to digest your last meal properly, allowing your blood test results to reflect your body’s natural baseline rather than a short-term change caused by food or drink.

Common Types of Fasting Blood Tests

Not all blood tests require fasting, but here are some of the most common ones that do: · Blood glucose test: Used to check for diabetes or prediabetes. · Kidney and liver function tests: Assess how well your liver and kidneys are working.

· Metabolic panels: Check various markers related to metabolism and overall health.

Fasting used to be standard for lipid panel tests, and your doctor may still ask you to fast, but it’s no longer routinely required. If you’re unsure whether you need to fast, just ask.

How to Prepare for a Fasting Blood Test

Your doctor will give you fasting instructions based on the specific blood test you’re taking. However, here are some general fasting guidelines to help you feel more prepared and informed:

Know how long to fast for a blood test: Fasting typically begins 8-12 hours before you test. If your test is in the morning, a great rule of thumb is to not consume any food or drinks (except water) after dinner the night before.

Drinking water is allowed – and encouraged: Unlike other beverages (including juice, tea and coffee), water won’t impact your results. In fact, it’s essential to drink water while you’re fasting to remain hydrated and make the blood draw easier.

Check your medications: Most medications are fine to take while fasting before your blood test, but some may need to be temporarily stopped to prevent blood clots. Talk to your doctor, and they’ll be able to advise you.

Avoid alcohol for 24 hours: Like other drinks, alcohol should be avoided in the fasting window. But for the most accurate results, it’s recommended to avoid alcohol for a full day before your blood test.

Don’t smoke before your fasting blood test: Smoking (including vaping) can affect the levels of certain blood biomarkers. If you’ve been asked to fast, you should try to refrain from smoking for the entire period.

Why Staying Hydrated is Important While you can’t eat before your test, drinking water is actually encouraged. Research shows you can have at least 300ml in the hour directly before your test with no impact to the results, and staying hydrated makes blood work easier by:

· Keeping your veins plump, making the blood draw quicker and easier.

· Preventing dizziness or lightheadedness while you’re fasting.

· Stopping dehydration from affecting your blood test results.

So, even though you can’t have your usual morning coffee, make sure you drink plenty of water. If you’re not sure how much water to drink before a blood test, just aim for your usual intake or sip water regularly in the hours leading up to your appointment.

Tips for Fasting Before a Blood Test

Feeling nervous about fasting before a blood test? Here are some practical tips to help make fasting as simple as possible:

· If possible, schedule your blood work in the morning so you can fast overnight while sleeping and avoid feeling as hungry during the day.

· Eat a nutritious meal packed with protein, fibre, and healthy fats as your last pre-fasting meal to help you feel fuller for longer.

· Heavy workouts can affect test results and use up your energy, so take it easy before your blood test and avoid strenuous exercise in the 24 hours leading up to your test.

· Bring a healthy snack (like a banana or granola bar) with you on the day of your test to eat after your fasting blood test and help you refuel.

Blood Test Services at Superdrug Clinics Superdrug Clinics offers professional blood work services, including common blood fasting tests. Whether you’re checking your cholesterol, blood sugar, or overall health, our trained nurses and phlebotomists are here to help.

To book a fasting blood test, choose your test and schedule a visit online or by calling our booking line. Your appointment will take place at your closest Superdrug Clinic, where our trained nurses and phlebotomists will take your blood sample. Once analysed, our medical team will review your results, and you’ll get a personalised digital report with advice tailored to you.

Book your blood test at Superdrug Clinics today for fast and reliable results.

Author bio:

This article is written by Hannah Thornley. Hannah turns complex health and medical topics into content that’s easy to understand – and hard to forget. With a degree in human physiology and five years of copywriting experience, she brings science to life with words that inform, engage, and inspire action