A scan takes minutes; the worry around it can take weeks. Much of that worry is about the unknown: what to wear, whether it will hurt, how loud it is, and how long until someone tells you something. This page follows the journey from the letter that arrives to the conversation about results, drawing on public patient information from radiology bodies and health services. Details differ by scan, by centre and by country, so your own appointment letter and imaging team come first. Nothing here is personal medical advice. For the methods themselves, see types of medical imaging.
Before the day: what the instructions are for
Most of what you are told to do has a reason. Fasting, drinking water, changing medicines, leaving metal at home: each is there because it makes the pictures clearer or the scan safer. RadiologyInfo.org says most X-ray exams need no special preparation, while for a CT exam that uses contrast material you may be told not to eat or drink for a few hours beforehand. For MRI, it says guidelines about eating and drinking vary between exams and facilities, and to take food and medications as usual unless told otherwise. For ultrasound, it says some scans call for no food or drink for up to 12 hours, a shorter time for babies and young children, while others call for drinking up to six glasses of water two hours before and not urinating, so the bladder is full.
The same pattern applies to what you wear. For X-ray, CT and ultrasound, loose comfortable clothing and leaving jewellery at home is the general advice, and you may be asked to change into a gown. For MRI the metal rules are stricter, since the scanner is a powerful magnet: the NHS says you may be asked not to wear anything with metal, such as jewellery, a bra, hair clips or hearing aids, to take coins and keys out of your pockets, to change into a gown if your clothes have metal parts such as zips, and not to wear make-up. For mammography, RadiologyInfo.org adds that deodorant, talcum powder and lotion should be avoided on the day.
Tell the team in advance, ideally when you book, about the things that affect safety. The NHS lists pregnancy or possible pregnancy, breastfeeding, medicines, asthma, kidney or thyroid problems, diabetes, allergies including to contrast dye, previous surgery and any metal in the body such as surgical clips, a pacemaker or dental work. RadiologyInfo.org adds that for an implanted device you should bring any pamphlet about it and give the name and manufacturer. Why these questions matter is explained in radiation, contrast and imaging safety, and the questions to ask before a scan page lists prompts for the conversation.
If you have had earlier scans at another hospital, try to bring them or have them sent. RadiologyInfo.org says older exams can be very helpful to the radiologist, who may compare them with the new images.
Nerves, noise and small spaces
Feeling anxious is common and nothing to apologise for. The NHS advises talking to a healthcare professional at the hospital before your appointment if you feel anxious about an MRI or CT scan or fear small spaces, and says you may be able to have a medicine to help you relax and can ask if someone can come with you. RadiologyInfo.org says that if you have claustrophobia or anxiety you should ask your doctor to prescribe a mild sedative before the date of your MRI, that you should not drive yourself home if you take it, and that open or wider-bore scanners exist for some exams. It also says that one out of every twenty people may require a mild sedative to remain calm during an MRI, and that if patients are properly prepared and know what to expect, it is almost always possible to complete the exam.
The National Institute of Biomedical Imaging and Bioengineering (NIBIB) lists coping mechanisms that include listening to music or watching a video, closing or covering the eyes, and holding a panic button. Whatever you choose, you will be given earplugs or headphones for the noise, and the radiographer controls the scanner from another room but can hear and speak to you throughout.
On the day, scan by scan
| Scan | What you are asked to do | What you may notice | Typical time |
|---|---|---|---|
| X-ray | Stay still, sometimes hold your breath for a few seconds | Painless; a cool room and cold plate | 15 to 30 minutes in all |
| CT | Lie on a bed that moves through a ring; breath-holds at times | Slight buzzing and clicking; warmth and a metallic taste if contrast is injected | Usually within 30 minutes |
| MRI | Lie still in a tunnel; wear earplugs or headphones | Loud tapping and thumping; slight warmth in the area scanned | 30 to 60 minutes, sometimes longer |
| Ultrasound | Lie on a couch while a probe with gel is moved over the skin | Pressure, sometimes tenderness; occasionally an internal probe | About 30 minutes, up to an hour |
| Nuclear medicine | Receive a tracer, wait, then lie still under a camera | A pin prick, sometimes a cold feeling up the arm | Tracer wait of seconds to days; imaging 20 minutes to several hours |
The technologist who guides you through this is described on the page about what a radiologic technologist does. They will position you, may use pillows, straps or pads to help you stay still, and may ask you to wait until they have checked that the images are good enough for the radiologist, because more may be needed. Moving blurs the pictures in the way it blurs a photograph, which is why you are asked to be still. For the finer differences between the scans, see X-ray, CT and MRI compared, ultrasound basics and nuclear medicine in plain terms.
If contrast is used
For contrast scans an intravenous line is placed in a hand or arm vein. RadiologyInfo.org says an iodine-based contrast injection can bring a warm, flushed feeling and a metallic taste for a few minutes, while gadolinium for MRI typically brings coolness at the injection site for a minute or two, and that barium swallowed for some X-ray exams tastes mildly unpleasant and turns bowel movements white for a few days. The NHS says that after contrast you may be asked to wait in hospital for up to 30 minutes to be sure there is no reaction. Reactions are described as uncommon and severe ones as very uncommon, and radiology departments are equipped to deal with them. Tell staff straight away if you feel unwell.
Afterwards
For most scans you can leave straight away and carry on as usual. RadiologyInfo.org says you can resume normal activities and diet after an MRI or CT if you were not sedated, and that increased fluid intake after iodine-based contrast helps eliminate it. After nuclear medicine, it advises drinking plenty of water to help flush the tracer out of the body and following the safety precautions you are given to avoid exposing other people. If you were sedated, the NHS says someone will need to collect you and you should not drive for 24 hours. For children, the parent's role and the question of sedation are covered in imaging, children and pregnancy.
How results reach you
The route is the same for nearly every scan. A radiologist, a doctor trained to supervise and interpret radiology exams, analyses the images and sends a signed report to the doctor who ordered the exam, who then discusses it with you. The timing varies a great deal. The NHS says X-ray results may come on the same day or at an appointment a few weeks later, and that CT and MRI results usually take 1 to 2 weeks, sometimes up to 4 depending on urgency and where you live. RadiologyInfo.org says that in some cases the radiologist may discuss results with you after the exam, and that some mammography facilities also notify you directly.
Many patients can now see reports in an online health record, sometimes before their doctor has. RadiologyInfo.org's advice is to remember that the report is not written for you but for your doctor, and not to make assumptions about what it means; it describes the stress and worry that can accompany a scan with the word "scanxiety". It suggests preparing questions about the findings, the impression and the next steps. A follow-up exam, it adds, may be requested to look at something with more views or a special technique, or to see whether anything has changed over time, and is often simply the best way to see whether treatment is working. The report's sections are explained in reading a radiology report.
Finally, silence is not a result. The NHS advises contacting the referring doctor if you have heard nothing after a few weeks, and RadiologyInfo.org says not to assume results are normal if you do not hear from your doctor or the facility.
Frequently asked questions
Do I have to fast before a scan?
It depends on the scan. RadiologyInfo.org says most X-rays need no special preparation, some CT and ultrasound exams call for fasting, and MRI rules vary by exam and facility. Follow the instructions in your own appointment letter.
What can I do if I am claustrophobic?
Ask your doctor or the hospital before the day. The NHS says you may be able to have a medicine to relax and bring someone with you, and RadiologyInfo.org mentions open and wider-bore scanners for some exams. NIBIB lists music, closing the eyes and a panic button as coping measures.
How long do scan results take?
It varies. The NHS gives same day to a few weeks for X-rays and 1 to 2 weeks, sometimes longer, for CT and MRI in England, while other health systems differ. Ask your imaging team when to expect yours.
Can I drive home after a scan?
Usually yes, unless you were sedated. The NHS says you should not drive for 24 hours after a medicine to help you relax, and RadiologyInfo.org advises arranging a ride home if you take a sedative for an MRI.
The short version
Preparation is mostly about telling the team what affects safety, following scan-specific instructions on food, drink and metal, and asking in advance about nerves. On the day the technologist guides you; afterwards you can usually carry on as normal. A radiologist reads the pictures and writes to your doctor, and results may take days or weeks, so ask when to expect them.