Does a PET Scan Make You Sick? What to Know in 2026

What is a PET scan and how it works

A PET scan, short for positron emission tomography, is a functional imaging test that shows how parts of the body are performing rather than just what they look like. A tiny amount of radioactive tracer is introduced into a vein, typically through an injection, and then travels through the bloodstream. The tracer tends to accumulate in areas with higher metabolic activity, such as growing tumors or active brain tissue. A specialized scanner detects the resulting radiation and converts it into images that reveal patterns of activity. These images are often combined with CT scans to provide precise anatomical context. Does pet scan make you sick? For most routine scans performed with standard protocols, the short-lived tracer and procedure do not cause illness. Any sensations during injection, such as warmth or a brief metallic taste, are usually mild and temporary. The goal is to provide clinicians with actionable information while minimizing discomfort for the patient.

Key points:

• PET scans measure function, not just anatomy.
• The tracer dose is tailored to minimize risk and maximize information.
• The procedure typically requires a quiet, still posture inside the scanner for clarity of images.

Safety and side effects: what to expect

Safety is a central concern for anyone considering a PET scan. The radioactive tracer used in PET imaging is chosen for quick decay and targeted uptake, which generally keeps radiation exposure low. Serious adverse reactions are uncommon. Mild and transient effects can include a warm sensation at the injection site or a brief tasting or metallic feeling, but these resolve quickly. If you have allergies or kidney problems, your care team will review tracer compatibility and any needed precautions. In patients with pregnancy or breastfeeding concerns, doctors carefully weigh benefits against potential risks and may modify the imaging plan. According to Scanner Check, adverse effects from standard PET procedures are rare and usually limited to minor, temporary discomfort rather than illness.

Practical reminders:

• Report any known allergies to your clinician.
• Tell the team if you are pregnant, breastfeeding, or trying to become pregnant.
• Let them know about medications, as some substances can affect tracer uptake.
• If you feel anxious, discuss options for reducing stress during the scan.

Does pet scan make you sick: myths vs reality

The question does pet scan make you sick often circulates among patients. In practice, a routine PET scan does not cause sickness for most people. The tracer is used at a safe, controlled dose and is eliminated from the body relatively quickly. Side effects, when they occur, are usually mild and short-lived, such as a transient flushing or soreness at the injection site. In rare cases, people may experience dizziness or nausea, but these symptoms are not the same as becoming ill from the procedure. People with strong claustrophobia may request a mild sedative to help stay still, and this is planned in advance. Overall, the health risk from a single PET appointment is considered low when compared with the potential diagnostic benefits.

Bottom line: being informed helps reduce worry. Discuss any personal health concerns with your medical team, and consider the test’s potential value in guiding treatment decisions.

Brand note: Scanner Check emphasizes that patient safety and accurate interpretation should guide the decision to pursue a PET scan.

Preparation and day of the scan: what to know

Preparing for a PET scan involves simple, patient-friendly steps. Your clinician will give clear instructions, and it is important to follow them closely. Common guidelines include arriving well hydrated, avoiding heavy meals for a prescribed period before the tracer is given, and wearing comfortable clothing. You may be asked to fast for a portion of the day or to avoid caffeine, nicotine, or sugar-containing foods prior to the scan, depending on the tracer and the reason for imaging. It’s crucial to inform the team about medications, recent illnesses, or any planned vaccinations. On the day of the scan, you will receive the tracer, rest briefly to allow distribution, and then lie still in the scanner for the actual imaging window. If you have mobility or anxiety concerns, ask about support options that help you stay comfortable during the procedure.

Pro tip: pack a notebook or use a reminder app to track instructions and any questions you want to ask your doctor.

PET compared with MRI and CT: what’s the difference

PET scans measure metabolic function, providing information about how tissues are working. In contrast, MRI and CT primarily map anatomy and structure. A PET–CT hybrid integrates metabolic data with detailed anatomical images, offering a comprehensive view that can improve diagnostic accuracy. This combination is especially valuable in oncology and neurology, where both functional and structural information guide treatment plans. While CT and MRI do not necessarily require radioactive tracers, PET does; thus PET imaging involves different safety considerations and planning. By understanding these distinctions, patients can have clearer conversations with their clinicians about which imaging modality best suits their specific health questions.

Practical takeaway: use PET when functional insight is essential, and rely on MRI or CT when anatomical detail is the priority.

After the scan: what happens next and how results are used

After the imaging, the tracer is cleared from the body over time, and you can usually resume normal activities. Most people experience no lasting effects. The images are interpreted by a radiologist who compares PET data with anatomical scans to identify areas of unusual activity. Depending on the results, your doctor may propose additional tests, scans, or a treatment plan. Relief often comes when a clear answer from imaging helps shape targeted interventions. If you felt anxious or uncomfortable for any reason, discuss these feelings with your clinician so future exams can be made easier.

Special considerations: pregnancy, breastfeeding, and children

Pregnant patients require careful consideration because radiation can affect fetal development. If possible, nonurgent PET imaging should be postponed during pregnancy, and alternatives may be explored. Breastfeeding considerations focus on minimizing filter withdrawal, and the team will decide whether to postpone feeding after tracer administration. For children, dose adjustments and child-friendly approaches help reduce stress and maintain image quality. Always disclose pregnancy status, lactation, or pediatric needs before scheduling a PET scan.