Last Updated on November 27, 2025 by Bilal Hasdemir

A PET scan, or Positron Emission Tomography scan, is a medical imaging technique. It shows how the body’s cells work, helping doctors find and treat diseases.

Even though PET scans are mostly safe, they can cause some side effects. Knowing what might happen can help reduce worry and get patients ready for the test.

This article will look into the possible pet scan side effects. It will also explain what a PET scan is, why it’s important, and how it helps in medical tests.

Key Takeaways

• Understanding the basics of a PET scan and its medical applications.
• Recognizing the possible side effects associated with PET scans.
• Learning how to prepare for a PET scan to minimize risks.
• Gaining insights into the diagnostic value of PET scans.
• Understanding the role of PET scans in disease management.

Understanding PET Scans: What They Are and How They Work

Positron Emission Tomography, or PET scan, is a cutting-edge medical imaging method. It gives deep insights into the body’s metabolic processes. This tool is key in managing and diagnosing many health issues, like cancer.

The Science Behind Positron Emission Tomography

A PET scan uses a tiny amount of radioactive tracer. This tracer goes to areas with lots of activity. When it decays, it sends out positrons that meet electrons, creating gamma rays.

The PET scanner catches these gamma rays. It makes detailed pictures of the body’s inside. Doctors say PET scans are great for seeing how tissues work. They help spot and track diseases.

Common Uses of PET Scans in Medical Diagnosis

PET scans are used in many ways, like finding and tracking cancer. They help see how cancer spreads and if treatments work. They also help in studying brain and heart issues.

PET scans give doctors the info they need to decide on treatments. This makes them a big part of modern medicine. They help improve patient care and outcomes.

The PET Scan Procedure: What to Expect

The PET scan procedure has several steps, from registration to recovery. Knowing these steps can ease any worries you might have.

Before Your Scan: Registration and Preparation

First, you’ll register at the imaging facility. You’ll give personal and medical info. Preparation is key for a good scan. You might be told to:

• Fast for a certain period before the scan
• Avoid strenuous exercise
• Remove any jewelry or metal objects
• Wear comfortable, loose-fitting clothing

Tell your doctor about any meds you’re taking and if you have diabetes or are pregnant.

During the Scan: The Imaging Process

During the PET scan, you’ll get a small amount of radioactive tracer. The scan takes about 30 minutes to an hour. You’ll lie on a table that slides into a scanner.

Remaining calm and steady is important for clear images. You might need to hold your breath sometimes.

After the Scan: Immediate Recovery

After the scan, you can usually go back to your normal activities. Drink lots of water to get rid of the tracer. Most people don’t feel any side effects, but if you do, they’re usually mild.

Activity	Recommendation
Hydration	Drink plenty of water
Physical Activity	Resume normal activities as advised by your doctor
Medication	Continue as usual unless instructed differently

“The PET scan has revolutionized the field of diagnostic medicine, giving us deep insights into the body’s metabolic processes.”

Nuclear Medicine Specialist

Knowing what to expect during a PET scan helps you prepare better. This makes the procedure and the days after it easier.

Common PET Scan Side Effects

It’s important to know about the side effects of PET scans. These scans use a radioactive tracer, which can cause side effects in some people. Knowing this helps patients prepare for the procedure.

Immediate Reactions After the Procedure

Most people don’t have severe reactions to PET scans. But, some may feel certain side effects right after. These can include:

• Dizziness or lightheadedness when standing up after the scan
• Nausea or feeling queasy, possibly from fasting or the tracer injection
• A metallic taste in the mouth after the tracer injection

These side effects are usually mild and go away quickly after the scan.

Short-Term Side Effects

Some people may also face short-term side effects from PET scans. These can include:

1. Fatigue: Feeling very tired, possibly due to the scan or the condition being checked
2. Headache: Some people get headaches after the scan, but the cause is not always known
3. Discomfort at the injection site: The area where the tracer was injected might be sore or bruised

Following the post-scan instructions from your doctor can help reduce side effects. It ensures the tracer is safely removed from your body.

Even though these side effects can be worrying, serious problems from PET scans are rare. It’s good to talk to your doctor about any worries or risks before getting a PET scan.

Radiation Exposure During PET Scans

It’s important for patients to know about radiation from PET scans. These scans use small amounts of radioactive tracers. They help diagnose and monitor health conditions.

How Much Radiation Is Used in a PET Scan?

The radiation from a PET scan varies. It depends on the tracer and the scan’s protocol. Usually, it’s between 4 to 7 millisieverts (mSv). This is similar to the yearly background radiation in the U.S.

Comparing PET Scan Radiation to Other Sources

Comparing PET scan radiation to other sources helps understand it better. For example, a chest CT scan has about 7 to 8 mSv. A chest X-ray is much less, at 0.1 mSv. Even though PET scans use radiation, they often provide valuable information.

PET scan radiation exposure is something to consider. But it’s part of a larger picture in diagnostic imaging. When comparing pet scan vs CT scan radiation, both use radiation. Yet, they serve different purposes and have different exposure levels.

The Radioactive Tracer: Understanding Its Effects

It’s key to know about the radioactive tracer for PET scan patients. This substance is injected to show how the body works.

How the Tracer Works in Your Body

The tracer sends out positrons. These meet electrons, making gamma rays. The PET scanner catches these rays, showing the body’s inside.

The process involves several key steps:

• The tracer is injected into the bloodstream.
• It builds up in active areas.
• The PET scanner detects the gamma rays emitted.

How Long Does the Tracer Stay in Your System?

The tracer’s half-life is short, usually hours. Most are gone in 24 to 48 hours.

Tracer Type	Half-Life	Elimination Time
Fluorodeoxyglucose (FDG)	110 minutes	24 hours
Other Tracers	Varies	24-48 hours

Doctors say, “The tracer’s short half-life lowers radiation risk.”

Drinking water helps get rid of the tracer. Listen to your doctor’s advice too.

Potential Allergic Reactions to PET Scan Components

PET scans are usually safe, but some people might have allergic reactions to certain parts. The main worry is the radioactive dye used in the scan. This dye is injected into the body.

Signs of an Allergic Response

Allergic reactions to the dye can show up in different ways. Common signs of an allergic response include:

• Itching or rash at the injection site
• Hives or redness on the skin
• Swelling, like of the face, lips, or tongue
• Difficulty breathing or shortness of breath

These symptoms can be mild or severe. In rare cases, a person might have a severe allergic reaction called anaphylaxis. This is a serious condition that needs quick medical help.

When to Seek Medical Attention

If you have any allergic reaction symptoms after a PET scan, get medical help right away. For mild reactions, talking to your healthcare provider is usually enough. But, if you have severe symptoms like trouble breathing, a fast heartbeat, or a big drop in blood pressure, go to the emergency room fast.

Knowing the signs of an allergic response and when to get help can help avoid serious problems with PET scan allergic reactions.

PET Scan Side Effects: What Research Shows

Research on PET scan side effects has given us a lot of information. PET scans are used to see how the body works. They show where energy is being used in the body.

Clinical Studies on PET Scan Safety

Many studies have looked into how safe PET scans are. They focus on the radioactive tracer and how patients feel during the scan. Most patients do okay with PET scans.

A study in the Journal of Nuclear Medicine found very few severe reactions. Less than 1% of patients had a bad reaction. This shows PET scans are generally safe for use.

Documented Adverse Events

Even though they are rare, some bad things can happen with PET scans. These include allergic reactions, feeling trapped during the scan, or problems with the tracer injection. It’s important to record these events to learn how to avoid them.

Adverse Event	Frequency	Severity
Allergic reactions	Rare	Mild to Severe
Claustrophobia	Occasional	Mild to Moderate
Injection complications	Rare	Mild to Severe

The table shows some bad things that can happen with PET scans. It tells us how often they happen and how bad they can be. Knowing this helps doctors and patients make better choices.

Looking at studies and reported problems helps us understand PET scans better. This knowledge helps keep PET scans safe for use in medicine.

Special Considerations for Diabetic Patients

Diabetic patients need to take extra steps before, during, and after a PET scan. This ensures their safety and the scan’s success. Managing diabetes is key during the PET scan process.

Blood Sugar Management Before and After the Scan

Diabetic patients should work closely with their healthcare provider. They need to manage their blood sugar levels before and after the PET scan. Following specific instructions on fasting, medication, and glucose monitoring is essential to avoid complications. They might need to adjust their medication or fasting period to keep their blood sugar safe for the scan.

Potential Complications for Diabetics

Diabetics undergoing a PET scan may face risks like hypoglycemia or hyperglycemia. These risks are higher if they fast or adjust their medication. It’s important to monitor blood sugar levels closely before, during, and after the scan. Patients should also know the signs of these conditions and when to seek medical help.

Understanding these special considerations helps diabetic patients prepare for a PET scan. It also helps them avoid complications.

PET Scans for Special Populations

PET scans are used in special groups like children and the elderly. These groups have unique needs that affect how PET scans are done and read.

Children and PET Scan Safety

PET scans help diagnose and track diseases in kids, like cancer and brain disorders. Making sure kids are safe during these scans is key. This means using the right amount of radioactive tracer to keep radiation low but image quality high.

Key considerations for pediatric PET scans include:

• Adjusted tracer doses based on body weight
• Use of sedation or anesthesia when necessary to prevent movement
• Careful monitoring for possible side effects

Elderly Patients: Additional Precautions

Older patients getting PET scans face extra health concerns. These can include other health issues and medicines that might change how the scan works or what it shows.

Consideration	Description
Comorbidities	Presence of other health conditions that may impact the PET scan
Medication Management	Potential interactions between medications and the PET scan tracer
Physical Limitations	Need for assistance or accommodations during the scan

PET Scans During Pregnancy and Breastfeeding

Using PET scans on pregnant or breastfeeding women is a tricky issue. It’s about balancing the benefits against possible risks. PET scans are useful for diagnosing, but their use in these situations needs careful thought.

Risks to Expectant Mothers and Fetuses

PET scans expose women to a small amount of radiation. This is a worry during pregnancy. The radioactive tracer can pass through the placenta, reaching the fetus. High doses of radiation might harm the fetus or increase cancer risk later in life.

Radiation Exposure Concerns:

• Fetal radiation exposure
• Potential for increased cancer risk in childhood
• Possible effects on fetal development

Recommendations for Nursing Mothers

There are worries about radioactive tracers in breast milk for nursing mothers. Most advice is to stop breastfeeding for a while after the scan. The exact time depends on the tracer used.

Tracer Used	Recommended Time to Suspend Breastfeeding
FDG (Fluorodeoxyglucose)	24 hours
Other Tracers	Variable, check specific guidelines

Nursing mothers should talk to their healthcare provider. This ensures they follow the latest guidelines.

Post-PET Scan Precautions

After a PET scan, it’s important to get rid of the radioactive tracer. This helps keep you and others safe. Knowing how to do this can make it easier.

Recommended Activities After Your Scan

There are things you can do to help your body after a PET scan. You should:

• Drink lots of water to get rid of the tracer.
• Stay away from pregnant women and young kids for a few hours.
• Go back to eating normally unless your doctor tells you not to.

“Hydration is key to flushing out the radioactive material,” he adds.

Hydration and Elimination of Radioactive Materials

Drinking water is very important after a PET scan. It helps spread out the radioactive tracer and helps it leave your body. You should drink at least 5 to 6 glasses of water in the 24 hours after your scan.

Activity	Benefit
Drinking plenty of water	Flushes out radioactive tracer
Avoiding close contact	Reduces radiation exposure to others
Resuming normal diet	Helps in recovery

By taking these precautions, you can lower the risks of PET scans. Always listen to your healthcare provider’s advice. They might have special instructions for you based on your health.

PET Scan vs. CT Scan: Comparing Side Effects

PET scans and CT scans are both important for finding and tracking health issues. But they have different side effects that patients should know about. The technology used in each scan and their risks are not the same.

Different Technologies, Different Risks

PET scans use a radioactive tracer that cells absorb. This lets doctors see how cells are working. CT scans, on the other hand, use X-rays to show the body’s inside parts.

PET scans might cause radiation exposure and allergic reactions to the tracer. CT scans, with their X-ray radiation, can raise cancer risk, more so in kids.

Combined PET/CT Scans: Cumulative Effects

Today, many tests use both PET and CT scans together. This gives doctors metabolic info from PET and detailed body images from CT. But, it means patients get exposed to more radiation.

This combined exposure can increase the total radiation dose and risks. Knowing the side effects of PET scans and CT scans is key to making smart choices about tests.

Long-Term Side Effects of PET Scans

PET scans are used a lot, and knowing their long-term side effects is key. They are mostly safe, but worries about the radioactive tracer used in them are growing. This concerns both doctors and patients.

Current Evidence on Repeated Exposure

Research on the long-term effects of PET scans is ongoing. Early studies show little immediate risk, but long-term exposure might raise concerns. It’s vital for patients to talk about their risks with their doctors.

• Some studies hint at a slight increase in cancer risk from repeated PET scans.
• Other research finds the benefits of PET scans in serious conditions often outweigh the risks.

Cancer Risk Assessment

Figuring out the cancer risk from PET scans involves many factors. These include the radiation dose, how often scans are done, and the patient’s health. The risk is generally low, but it’s not zero, mainly for younger people or those getting many scans.

To lower risks, doctors follow strict guidelines. They make sure PET scans are used wisely and doses are as low as possible. Patients can also help by following post-scan advice, like drinking lots of water to get rid of the tracer.

Psychological Effects and Coping with Scan Anxiety

PET scans are key for diagnosis but can deeply affect patients’ minds. They are mostly safe but can make many anxious and stressed.

Managing Stress Before and During the Procedure

It’s important to manage stress and anxiety before and during a PET scan. Using relaxation techniques like deep breathing or meditation can help. Knowing what the scan is about can also ease worries.

Having someone you trust with you during the scan can offer comfort. Medical staff can also provide reassurance and help ease your fears.

Dealing with Anxiety While Waiting for Results

Waiting for PET scan results can be tough. The not knowing can make anxiety worse. Doing things to distract yourself or practicing relaxation can help.

Staying in touch with loved ones can also help. If anxiety is too much, getting professional help is a good idea.

Understanding the mental impact of PET scans and finding ways to cope can make the experience easier.

When to Contact Your Doctor After a PET Scan

Knowing when to seek medical help after a PET scan is key to your health. PET scans are usually safe, but it’s important to know about possible side effects and when to get help.

Warning Signs That Require Medical Attention

Watch for signs of an adverse reaction or complication after a PET scan. These include:

• Severe allergic reactions, such as difficulty breathing or swallowing
• Increased heart rate or palpitations
• Dizziness or fainting
• Pain or swelling at the injection site

If you notice any of these symptoms, contact your doctor right away. They can tell you what to do next.

Normal vs. Abnormal Post-Scan Symptoms

Telling normal from abnormal symptoms after a PET scan can be tricky. Mild side effects like fatigue or a metallic taste are usually okay and temporary. But, if you’re not sure or if symptoms last, talk to your healthcare provider.

Knowing when to reach out to your doctor after a PET scan can ease your worries. If you’re dealing with abnormal post-scan symptoms or health concerns, contact your medical team without delay.

Conclusion

Knowing about PET scan side effects is key for patients. This article covered PET scans’ uses, how they work, and the risks. We looked at what to expect and how to stay safe.

A PET scan uses a radioactive tracer, which might cause some side effects. These are usually mild and short-lived. You might feel anxious, claustrophobic, or have an allergic reaction to the tracer.

It’s important to follow your doctor’s instructions before the scan. Tell them about any health issues or allergies you have. This way, you can reduce the risks and have a better experience.

In summary, PET scans are generally safe, but knowing the possible side effects helps. Being prepared and understanding the process can make your experience smoother. This guide is a helpful resource for anyone facing a PET scan.

FAQ

Reference

1. Sanchez-Crespo, A. (2013). Clinical radiation exposure and risk associated with nuclear medicine procedures. Physical and Engineering Sciences in Medicine, 36(4), 293–306. https://pubmed.ncbi.nlm.nih.gov/23990192/