Before Your CT Scan: Confirm the Scan Plan, Contrast Agent, and How to Get Your Images

After receiving an order for a CT scan, ask the ordering doctor what question the scan is intended to answer. Then check with the center performing the scan about the body area to be scanned, whether contrast will be used, preparation requirements, and how to get your images. If you may be pregnant or have had a reaction after receiving contrast before, tell the team when booking.[1][2]

Key Points

• CT uses X-rays. The body area, scanning technique, and need for repeated image acquisition should match the clinical question.
• Contrast can be given in different ways, and some scans do not need it. Report previous reactions, kidney disease, medicines, and possible pregnancy in advance.
• Instructions for fasting, drinking, and medicines vary by scan. Do not stop medicines on your own or follow someone else’s preparation instructions.
• The report and original images are two separate items. After giving them to the receiving doctor, confirm that the doctor can access and view the images.

When Booking: Confirm What Is Planned

Ask the ordering doctor: “Which body area will this scan examine, and what is it meant to assess? Can previous scans be used for comparison? Do I need a scan without contrast, with contrast, or at different times after contrast is given?” Different scan plans answer different questions; more scans are not automatically better. CT involves radiation. The dose varies with factors such as the body area scanned, equipment, patient body size, and number of image acquisitions. Typical figures online do not represent your individual dose. Your doctor will weigh the information the scan can provide against its risks.[6] If you are concerned about the dose, ask whether another option could answer the same question. Do not cancel an urgently needed scan on your own. For children, the team should adjust the scan settings for age and body size. For people without symptoms, the US FDA currently does not consider whole-body CT screening to have a clear benefit.[2][3][5]

Confirm the facility location, appointment time, whether contrast will be injected or taken by mouth, whether fasting is required, and exactly when to start fasting. Contrast-enhanced CT using an injection into a vein commonly uses iodine-containing contrast. Contrast taken by mouth or given by other routes serves different purposes; ask the center to explain your scan plan.[1][3] Bring the scan order, recent relevant reports, and the complete images from previous CT scans. Ask whether the center can accept and read them. If sedation or anesthesia is needed, separately confirm preparation and escort requirements with the responsible team. If you have not followed the fasting or drinking instructions, tell the scan center immediately. If sedation or anesthesia is involved, also tell the anesthesia team what you ate or drank and when, so the team can decide whether to proceed.[9]

Before the Scan: Share Your Health Information

Give accurate information about your medicines and supplements, kidney disease or recent changes in kidney function, dialysis, diabetes, thyroid problems, asthma, allergies, and whether you are pregnant, may be pregnant, or are breastfeeding. If you felt unwell after receiving contrast before, try to provide the agent’s name, when the reaction occurred, the specific symptoms, and what treatment you received, rather than simply saying “allergy.” Bringing previous records helps the team decide on the scan plan. A broad label such as “iodine allergy” does not identify the substance involved or what happened. Be especially specific about any previous reaction to the same type of contrast.[1][2][4]

If you are receiving dialysis, do not change your dialysis schedule on your own; ask the dialysis and imaging teams to confirm the plan together. If your doctor prescribes medicines before the scan because of a previous contrast reaction, you still need to tell staff about that reaction: these medicines cannot guarantee that another reaction will be completely prevented.[4]

If you take metformin, insulin, or other medicines, ask the responsible team whether any changes are needed for this scan and when to resume them. Do not stop medicines on your own. The scan center may request a kidney function test based on your circumstances. Ask the center to confirm whether testing is needed and whether previous results can be used.[1][2]

During the Scan and Before You Leave

Follow staff instructions to remove metal objects from the area being scanned, stay still, or briefly hold your breath. Tell the team in advance if you cannot lie flat, raise your arms, or hold your breath. During the injection, tell staff immediately if you have pain or swelling at the injection site or any breathing discomfort. After the scan, stay for observation as instructed by the center, and confirm how to get help if you develop a rash, difficulty breathing, or other symptoms.[2]

Confirm when and by whom the report will be explained, and where to obtain the official report and complete DICOM images. If contrast was used, ask whether you can obtain its name and administration record; keep dose information too, if available. After giving the materials to the doctor caring for you, confirm that the doctor can open the images and knows when you will discuss the results. Even if the report says “normal,” ask what question it answered and what happens next. If the scan finds a new change unrelated to the reason for this scan, ask the doctor to compare it with previous images and explain whether follow-up is needed, when it should happen, and who will arrange it.

Frequently Asked Questions

Does every CT scan need a contrast injection?

No. Whether contrast is used and how it is given depend on the purpose and plan for the scan. Confirm this with the center when booking.[1][2]

Is it normal to feel warm during a contrast injection?

Some people briefly feel warm or notice a metallic taste in their mouth. Tell staff about any discomfort, and report difficulty breathing or pain and swelling at the injection site immediately.[2]

Can I have a contrast-enhanced scan if I have had a contrast reaction before?

Do not decide on your own. Provide the agent’s name and records of the reaction and treatment in advance. The radiology team and ordering doctor will assess whether to change the scan plan or take other measures.[1]

Does a seafood allergy mean I cannot receive iodine-containing contrast?

The decision should not be based on a seafood allergy alone. Report all allergies, especially any previous reaction to CT contrast, so the team can assess your situation.[4]

Do I always need to stop metformin?

Not necessarily. Any change depends on the scan, kidney function, and specific medical instructions. Ask in advance when to take your last dose and when to resume it. Do not stop it on your own.[4]

What if I am pregnant or may be pregnant?

Tell the ordering doctor and radiology team before the scan. The body area being scanned affects whether the fetus is directly exposed to radiation; abdominal or pelvic scans especially need discussion. Your doctor will choose a plan based on urgency, whether ultrasound or MRI could answer the same question, and possible risks. Do not withhold this information or cancel an urgently needed scan on your own.[7]

If I am breastfeeding, do I need to pause after receiving contrast?

The UK NHS Specialist Pharmacy Service states that people breastfeeding healthy, full-term infants generally do not need to pause breastfeeding after receiving the commonly used iodine-containing contrast agents listed in its guidance.[8] Tell the scan team if your baby was born prematurely or is unwell, and confirm the name of the contrast agent being used. If you also receive sedation or other medicines, ask a doctor to check your breastfeeding arrangements separately.

Can scan results alone determine treatment?

Images answer questions about a particular time and body area. A doctor needs to interpret them alongside your medical history, other tests, and clinical condition. Ask the doctor to explain the next step, and do not draw conclusions from a single word in the report.

What should I do if I develop severe symptoms after leaving?

If you develop severe symptoms such as difficulty breathing, swelling of the face or throat, or fainting, contact local emergency services immediately. For other unusual symptoms, follow the scan center’s instructions and use the phone number it provided.[2]

Sources

1. RadiologyInfo: How to Prepare for Your CT Exam, checked on 2026-11-06.

2. NHS: CT Scan, checked on 2026-11-06.

3. RadiologyInfo: Body CT, checked on 2026-11-06.

4. American College of Radiology: Manual on Contrast Media, access page checked on 2026-11-06; specific chapters and local hospital medication rules await professional review.

5. FDA: CT Scans, Radiation Protection for Children, and Whole-Body Scanning Without Symptoms, checked on 2026-11-06.

6. FDA: Radiation Risks of CT, checked on 2026-11-06.

7. RadiologyInfo: CT Safety During Pregnancy, checked on 2026-11-06.

8. NHS Specialist Pharmacy Service: Using Contrast Agents During Breastfeeding, checked on 2026-11-06; this advice applies to healthy, full-term infants and the commonly used contrast agents listed in the article.

9. NHS: Preparing for Surgery and Fasting, checked on 2026-11-06; follow the responsible team’s instructions for preparation for the specific scan and anesthesia.