Preparing for Your PET/CT Appointment: Confirm the Tracer, Blood Glucose Plan, and Previous Images

EastMedGo Nov 6, 2026

After booking a PET/CT scan, ask the imaging center for preparation instructions specific to your scan. Tell the center the purpose of the scan, the tracer name, your recent treatment dates, and your medication list. Contact the center before the scan, especially if you have diabetes, might be pregnant, or are breastfeeding. After the scan, confirm when and how the report and original images will reach the referring doctor. This guide is mainly for adults; confirm preparation and low blood glucose treatment for children with the pediatric and imaging teams in advance.

Key Points

PET/CT preparation varies with the tracer, the purpose of the scan, and your circumstances. Do not apply the fasting times for another scan to your appointment.[1][2]
If you have diabetes, coordinate meals and medicines with the imaging center and the doctor who manages your blood glucose in advance. Do not stop medicines, increase doses, or extend fasting on your own.[1][2]
Recent surgery, treatment, or infection may affect image interpretation. Give the team a list of dates so they can decide when the scan should take place.[2]
PET/CT has limitations. Abnormal uptake does not always mean a tumor, and a normal result does not necessarily rule out every problem. Ask the referring doctor to explain the findings alongside pathology results and other tests.[1][4]

Check Your Appointment Details First

Using your referral or appointment details, ask the imaging center: What tracer will be used? What clinical question should the scan answer, and which parts of the body will be scanned? Will the CT part require iodine-based contrast? The radioactive tracer used for PET and iodine-based CT contrast are different substances. If your scan includes contrast-enhanced CT, tell the center about any previous contrast reactions, kidney problems, and medicines you take. Ask whether you need to provide recent kidney function results.[1][3]

Preparation can differ between scans. For example, Cambridge University Hospitals uses different dietary preparation for routine FDG cancer scans and FDG scans for cardiac sarcoidosis, while some PSMA scans listed by the same hospital require no fasting. These are only examples of that hospital’s different protocols; follow the written instructions from the center performing your scan.[2]

Tell the Imaging Center About Your Circumstances in Advance

Contact the nuclear medicine department as soon as possible after booking and tell them about:

Your type of diabetes, recent blood glucose levels, any episodes of low blood glucose, and your use of insulin, tablets, or an insulin pump;
Possible or confirmed pregnancy, or breastfeeding;
All medicines and supplements, previous allergies, and reactions to contrast;
Recent surgery, biopsy, radiotherapy or chemotherapy, other cancer treatments, injections to increase white blood cells, infection, or fever, with the relevant dates;
Difficulty lying flat or staying still, pain, claustrophobia, or a need to take medicines at set times.[1][2]

If you have diabetes, ask the imaging center to specify your appointment time, meal and medication plan, when to check your blood glucose, the acceptable blood glucose range for this scan, and whom to contact and what to do if your level is outside that range. Agree on a low blood glucose treatment plan in advance with the doctor who usually manages your diabetes, and ask what you should bring. If the two teams give different instructions, ask them to coordinate. Do not stop medicines, increase insulin, or deliberately fast longer on your own to make the appointment.[1][2]

If you suspect low blood glucose while preparing for the scan, treat it first. Do not wait just to maintain your fast. Adults with diabetes who are alert, can swallow safely, and can treat themselves should immediately follow their agreed low blood glucose plan if their blood glucose is 3.9 mmol/L (70 mg/dL) or below, or if they have symptoms of low blood glucose but cannot check it at that time. If you do not have a plan, take 15 grams of fast-acting carbohydrate, such as enough glucose tablets to provide 15 grams of sugar according to the package, or about 120 milliliters of regular fruit juice. Sugar content varies between drinks, so check the label.[6][8]

Check again after 15 minutes. If your blood glucose is still 3.9 mmol/L (about 70 mg/dL) or below and you can still swallow safely, you can take another 15 grams of fast-acting carbohydrate and check again after another 15 minutes. Contact a healthcare professional as soon as possible. If your blood glucose remains low after repeated treatment or your symptoms do not improve, seek emergency medical help immediately; do not wait alone. If you still cannot measure your blood glucose, contact a healthcare professional and arrange a measurement as soon as possible. Seek emergency help immediately if symptoms continue or worsen. Once your blood glucose has recovered and symptoms have improved, if you cannot eat a meal straight away, have a snack containing carbohydrate as advised by your healthcare professional to prevent another drop. Individual circumstances, such as using an automated insulin delivery system, may require a different plan; confirm this with your diabetes team in advance.[6][8]

If you become confused, cannot swallow safely, need someone else’s help to treat the episode, have a seizure, or lose consciousness, call emergency services immediately. In mainland China, call 120; elsewhere, call the local emergency number. Do not give food or drink to someone who cannot swallow safely or is unconscious. If you are in hospital, call the healthcare staff immediately.[6][7][8] After treatment, tell the imaging center when it happened and what you ate, drank, or took as medicine. The center will decide how to arrange the scan.

Follow the Instructions for This Scan

Ask the center to put in writing when dietary restrictions begin, whether you may drink plain water, and how to manage exercise and your usual medicines. If anything remains unclear after you receive the instructions, call to confirm before starting preparation. Cambridge University Hospitals requires patients having a standard FDG scan to drink only plain water for the six hours before their appointment and avoid strenuous exercise for the preceding 24 hours. Other protocols may differ; these timings do not replace your own appointment instructions.[2]

If the timing of your food, drink, exercise, or medicines has not matched the instructions, or if you may be late, contact the center as soon as possible. Explain what happened and when, so the center can decide whether to proceed or reschedule. The tracer has a limited usable time, so arriving late may affect your scan that day.[1] Do not hide the fact that you have eaten, drunk, or taken medicines.

Bring Previous Images and Arrange the Scan Day and Transfer of Results

Bring your referral, appointment confirmation, medication list, relevant pathology results and treatment timeline, and previous PET/CT, CT, or MRI reports and image files. Ask the center in advance which formats it accepts and how to submit files securely. If another hospital holds your previous images, contact that hospital to request them. Previous images help the doctor interpreting the scan make comparisons.[4] Before the scan, confirm with the receiving team that the files open and ask whether any image sequences or reports are missing. If previous images are unavailable, ask whether your consultation can go ahead using the available information and how to provide the missing images later.

Check in at the designated hospital site as instructed. After the injection, you will usually need to rest quietly before lying still on the scanning table. Your total time at the center includes preparation and waiting, not just the scan itself.[1][2] Tell staff immediately if you have pain or swelling at the injection site or feel unwell during the scan. Before leaving, ask for specific instructions about drinking fluids, breastfeeding, and contact with pregnant people or young children. Follow the instructions for the tracer used in your scan and the center’s guidance.[1][5]

Ask when and how you can obtain the formal report, original PET/CT images, and fused images, whether they will be sent directly to the referring doctor, and who will explain the results. If you need to take them back to your home country or give them to another hospital, first ask the receiving team which formats and submission methods it accepts. If you have not received them by the agreed time, contact the imaging center and let the referring doctor know. Once the files arrive, ask the receiving team to confirm that it can access and view them.

Frequently Asked Questions

1. What if the tracer name is not on my appointment confirmation?

Contact the imaging center with your appointment details and referral. Ask for the tracer name and its preparation requirements; do not assume that the usual FDG instructions apply.

2. Can I still have the scan if I accidentally ate something?

Tell the center as soon as possible what you ate and when. The center will decide whether any adjustments or rescheduling are needed. Do not hide this to keep your appointment.

3. What should I do if my blood glucose is high or low before the scan?

Contact the imaging center and the doctor who manages your blood glucose as soon as possible. Tell them your reading and symptoms, and follow the plan they provide for this appointment. Do not take extra medicine on your own. If you suspect low blood glucose, treat it first as described above. If high blood glucose is accompanied by symptoms such as vomiting, deep and rapid breathing, marked drowsiness, or confusion, seek emergency care or call emergency services immediately. Do not wait for a response about your appointment.[9]

4. How long must I wait after recent surgery or treatment?

There is no single waiting period that applies to every situation. Tell the referring doctor and nuclear medicine team the dates of your surgery, radiotherapy, chemotherapy, and other treatments, along with the purpose of the scan, so they can decide on the timing.[2]

5. Do “bright spots” on PET/CT mean cancer?

Not necessarily. The scan shows how the tracer is distributed in the body, and conditions such as inflammation can also affect the findings. The doctor needs to interpret them alongside other images, pathology results, and your medical history. Further tests may still be needed.[1][4]

6. If the scan is normal, can I skip further tests?

Do not cancel other tests or follow-up appointments on your own just because your PET/CT is normal. Give the results to the referring doctor and discuss the next steps in light of the original concern, pathology results, and other images.[3][4]

7. What if I cannot lie flat or am worried about enclosed spaces?

Tell the center about your specific difficulties in advance. Ask whether your position can be adjusted, pain relief provided, or other support arranged. If sedation is needed, first ask the team whether it is suitable for you and how to arrange someone to accompany you and your journey home that day.[1][5]

8. Why do I need the original images if I already have the report?

The doctor seeing you may need to review the full images and compare them with other scans. First ask the receiving team which image format it needs, then request it from the imaging center. Receiving the report alone does not mean the images have been successfully transferred.[4]

Sources

The following resources were checked on November 6, 2026. Follow the treating center’s instructions for your specific appointment, medicines, and scan arrangements.