How to Prepare for a PET Scan: Instructions and Recommendations

4 min read

If you’ve been recommended a PET scan and you’re not sure what to expect, you’re not alone. This type of exam can feel a little intimidating at first, but with the right information, you can face it with confidence. In this article, we will guide you step by step on how to prepare for a PET scan, what to expect during the procedure, and answer some frequently asked questions that you probably have.

What is a PET Scan and How Does It Work?

Imagine your body as a bustling city, with thousands of processes happening every second. A PET scan acts like a traffic supervisor that not only watches how the cars (your organs and tissues) are moving but also how those vehicles are functioning (the cells in your body).

A PET scan is an imaging test that uses a small amount of radiotracer, a radioactive substance injected into your body, to help doctors see how your organs are functioning in real-time. Unlike other scans like CT scans or MRIs, which only show static images, the PET scan shows the activity within your organs, which helps detect health issues at much earlier stages.

If you’re experiencing concerning symptoms like unexplained seizures, memory loss, or chronic headaches, it may be time for advanced imaging. [Discover the neurological symptoms you should never ignore.]

Difference Between PET Scan, CT Scan, and MRI

It’s normal to get confused with all the medical terms. Here’s a quick comparison:

Test	Technology Used	What It Shows	Benefits
PET Scan	Radiotracer (radioactive material)	Organ function (cellular activity)	Detects early diseases like cancer and brain disorders
CT Scan	X-rays	Images of organs and structures	Quick and accessible, useful for detecting fractures and cancer
MRI	Magnetic resonance imaging	Soft tissue details	No radiation, excellent for brain tissues

As you can see, each test has its own purpose, and the PET scan is especially helpful for seeing how cells are behaving in real-time.

How to Prepare for a PET Scan?

PET scan preparation matters more than most people think. Small choices—like what you eat, how much you move, and even whether you feel cold—can change how your body uses the tracer. That can make images harder to read. If you’ve been asking how to prepare for a PET scan, use this simple checklist to stay on track.

General PET Scan Preparation Instructions

The most important part of pet scan preparation is sharing the right information with your care team before scan day. Tell them if you have:

• Diabetes or trouble with blood sugar
• Pregnancy or you might be pregnant
• Breastfeeding
• Kidney problems (especially if you’re also getting CT contrast)
• Recent illness, infection, or fever
• Anxiety or claustrophobia (fear of tight spaces)
• Trouble lying still because of pain, tremor, or back/neck issues

Also share a complete list of:

• Prescription medicines
• Over-the-counter medicines
• Vitamins and supplements

This is essential pet scan preparation because some conditions (and sometimes certain medicines) can affect how your body absorbs the tracer. When your team knows your full history, they can give you the safest plan and the clearest images.

Pro tip for pet scan prep: If you think you may need a calming medicine for anxiety, ask ahead of time—not in the waiting room.

Diet and Food Restrictions

For many PET scans, you’ll be asked not to eat for several hours before the exam. This is one of the most common PET scan preparation rules because food—especially sugar and carbs—can change how cells use glucose. That can make the scan harder to interpret.

A simple way to remember it:

The “fasting window”

• Stop eating for the time your provider tells you (often several hours).
• Water is usually allowed and encouraged unless your team says otherwise.

The day before, some centers recommend lower-carb meals the day before. That means choosing foods like:

• Eggs, chicken, fish, tofu
• Non-starchy vegetables (salad greens, broccoli, cucumbers)
• Plain water

And limiting foods like:

• Candy, desserts, sweet drinks
• Bread, pasta, rice
• Sugary cereals, pastries, fruit juice

Because every PET exam is a little different, follow the exact instructions you’re given. If your center does not mention a special diet, don’t guess—call and ask. The goal of pet scan preparation is consistency, not perfection.

Exercise and Movement: A Commonly Missed PET Scan Prep Step

Many people focus on fasting and forget this: hard exercise can change tracer uptake in your muscles. That can create “hot spots” that are not related to disease.

For better images as part of pet scan prep:

• Avoid heavy workouts (running, intense gym sessions, heavy lifting) the day before or as instructed.
• On scan day, arrive early enough that you can sit calmly without rushing.

If your scan is for the brain, your team may also ask you to:

• Rest quietly before the scan
• Avoid stressful activities right before the tracer uptake period

This is an easy pet scan preparation step that can make a real difference in image clarity.

Medications and Special Conditions

A top question in how to prepare for a PET scan is: “Should I take my medications?”

In many cases, you can keep taking your usual medicines with water. But there are exceptions, and the rules can change based on:

• The type of PET scan
• Your medical history (especially heart and brain conditions)

Pet scan prep tip: Don’t stop medications on your own. Ask your ordering provider or imaging team

What to Expect During a PET Scan?

Now that you know the main PET scan preparations you need, let’s talk about what will happen during the PET scan. It’s completely normal to feel nervous, but knowing what to expect can help ease your mind.

Step-by-Step Procedure

The first thing that will happen is that you will receive an injection of a radiotracer, a radioactive substance that your body will absorb. After the injection, you will need to wait for about 30 minutes to 1 hour for the radiotracer to spread throughout your body. During this time, you should stay calm and rest.

In some cases, if you are getting a PET/CT scan, a contrast dye will also be administered to improve the image quality.

Duration of the PET Scan

The actual scanning process usually takes about 20-30 minutes, but it’s important to stay as still as possible to get clear images. After the scan, you may need to wait a few minutes while the technologist reviews the images to ensure everything is clear.

Risks and Side Effects

A PET scan is generally a safe procedure, and side effects are extremely rare. The amount of radiation used is minimal, and it doesn’t stay in your body for long. To help eliminate any remaining radiotracer, you’ll be encouraged to drink plenty of water after the test.

Ready to take the next step? Book a test

What Does a PET Scan Show? A Clear Look Inside Your Body

A PET scan (Positron Emission Tomography scan) is a powerful imaging test that shows how tissues and organs are functioning in real time. Unlike traditional imaging techniques like X-rays or CT scans, which reveal the structure of the body, a PET scan shows metabolic activity. This means it highlights areas where cells are more active than normal, helping doctors detect disease at a very early stage.

So, what does a PET scan show exactly? It can reveal signs of cancer, heart problems, and brain disorders before structural changes become visible. For example, it’s commonly used to detect cancer spread, evaluate blood flow to the heart, or examine brain function in conditions like Alzheimer’s or epilepsy.

To sum up, what a PET scan shows is more than just images — it uncovers what’s really happening inside your body, at a cellular level. That’s why it’s such a vital tool for early diagnosis and treatment planning.

How Long Does a PET Scan Last? Everything You Need to Know

If you’re preparing for your first PET scan, it’s natural to wonder: how long does a PET scan last? On average, the entire process takes about 1.5 to 2 hours, but the actual scan time is usually only 20 to 30 minutes.

Here’s a breakdown:

1. Preparation (30–60 minutes): Before the scan, a small amount of radioactive tracer is injected, and you’ll need to wait quietly while your body absorbs it.
2. The scan itself (20–30 minutes): You’ll lie still on a table while the scanner captures detailed images of your organs and tissues.
3. Post-scan (few minutes): Once it’s done, you can usually return to your normal activities right away.

So, how long does a PET scan last? While the scanning part is quick, plan for about two hours in total from start to finish.

How long a PET scan lasts can vary slightly depending on the area being examined or if it’s combined with a CT scan, but in most cases, it’s a smooth and efficient process.

Imaging Procedures

Here’s a helpful comparison of common imaging exams to help you understand the differences and know which one might be right for you:

Test	Technology Used	What It Shows	Benefits	Drawbacks
PET Scan	Radiotracer (radioactive material)	Organ function (cellular activity)	Detects early diseases like cancer and brain disorders	Higher cost, not suitable for pregnancy
CT Scan	X-rays	Images of organs and structures	Quick and accessible, useful for detecting fractures and cancer	Doesn’t show cellular activity, uses radiation
MRI	Magnetic resonance imaging	Soft tissue details	No radiation, excellent for brain tissues	Slower, more expensive, can be uncomfortable

This type of information can help you make informed decisions about which procedure is most appropriate for your needs.

Pet scan prep

A PET scan can be a valuable tool for diagnosing and monitoring certain health conditions. With this guide, we hope you feel more prepared and confident for your exam. Remember, your well-being is the most important thing, and being well-informed is key to facing any medical procedure with ease.

PET scans are often used in the diagnosis and treatment planning for epilepsy. [Learn more about how epilepsy is diagnosed and treated here.

Frequently Asked Questions About: How to prepare for a pet scan

1. How long before a PET scan should I stop eating?

To get accurate results, it is recommended that you do not eat for at least six hours before your PET scan. Water is the only allowed liquid, so stay hydrated. If you have diabetes, your doctor may adjust this recommendation, so be sure to follow their specific instructions.

2. Can I take my medications before a PET scan?

In most cases, you can continue taking your usual medications, but there are exceptions. If you take medications that might interfere with the results, such as those used for heart or brain conditions, your doctor will give you specific instructions. It’s always best to confirm with your doctor before the scan.

3. Is it safe to have a PET scan if I’m pregnant or breastfeeding?

PET scans are not recommended for pregnant or breastfeeding women due to the radiation involved in the procedure. If you think you might be pregnant or are breastfeeding, it’s very important to inform your doctor before scheduling the exam. The radiation could be harmful to the fetus or infant.

4. How should I prepare if I have diabetes?

If you have diabetes, your preparation for the PET scan should be more careful. Typically, you will need to adjust your medications and diet to ensure that your glucose levels are controlled before the test. Make sure to follow your doctor’s instructions closely, as high or low blood sugar can affect the results.

5. What happens if I move during the PET scan?

It is crucial that you remain as still as possible during the scan. Any movement can blur the images and affect the quality of the diagnosis. If you feel uncomfortable or anxious, let the technologist know, and they can provide options, such as a mild sedative, to help you relax during the procedure.