CT scan (Computed tomography (CT) scan)
A scan that uses X-rays and a computer to build detailed cross-section pictures of the inside of the body, often used to look at bones, the chest, the tummy or to check for bleeding.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- A CT scan uses X-rays to give fast, detailed pictures, and is especially good for bone, the lungs, the tummy and finding bleeding.
- It involves a small dose of radiation, so it should be done when it will genuinely help — the benefit usually outweighs the small risk when a scan is needed.
- There is usually no recovery; results normally come as a written report in about 1–2 weeks, sooner if urgent.
- Tell the team if you are or might be pregnant, have kidney problems, diabetes, a thyroid condition, or a previous contrast reaction, as these affect the use of contrast dye.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your radiologist will give you advice for your situation.
Gives fast, detailed cross-section pictures of bones, the chest, the tummy and pelvis
Pregnancy, unless the scan is genuinely needed and cannot wait or be replaced by a radiation-free test.
You lie still on a bed that passes through a ring for a few minutes, sometimes holding your breath. If contrast is given you may feel a brief warm flush.
A clear route to your written report and a named person to explain it.
You lie still on a bed that passes through a ring for a few minutes, sometimes holding your breath. If contrast is...
You can normally eat, drink, drive and return to work immediately. If you had contrast, you may be asked to wait a...
Drinking fluids normally helps your kidneys clear the dye. Seek advice if you develop a rash, swelling or...
A radiologist reviews the images and sends a report to the doctor who referred you, who discusses the results and...
What is a CT scan?
A CT (computed tomography) scan uses X-rays and a computer to build detailed 'slice' pictures of the inside of your body. It is quick and very good at showing bones, the lungs, internal bleeding, and many problems in the chest, tummy and pelvis.
A doctor usually requests a CT to investigate a symptom, check an injury, look for or stage a cancer, or guide a procedure. The scanner takes the images; a radiologist (a doctor who specialises in reading scans) then studies them and writes a report.
Because it uses X-rays, a CT involves a small dose of radiation. For a person who needs the scan, the benefit usually clearly outweighs this small risk, but it is a reason not to have CT scans unnecessarily. A normal scan does not rule out every illness, and CT can pick up harmless 'incidental' findings that lead to more tests.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
CT compared with MRI
| CT | MRI | |
|---|---|---|
| Uses radiation | Yes (X-rays) | No |
| Best for | Bone, lungs, bleeding, emergencies | Soft tissues, brain, spine, joints |
| Speed | Fast (minutes) | Slower (often 20–60 min) |
| Contrast | Iodine-based | Gadolinium-based |
| Metal implants | Usually fine | Often a problem — must be checked |
Neither scan is 'better' overall — they answer different questions. Your doctor and the radiologist choose based on what needs to be seen and how quickly.
Preparing for your scan
- Tell the team if you are or might be pregnant — CT uses X-rays, so they will check whether the scan is needed or can wait.
- Mention kidney problems or reduced kidney function; a blood test is sometimes needed before iodine contrast.
- Say if you have diabetes (especially if you take metformin), a thyroid condition, asthma or a previous reaction to contrast dye.
- Follow any instructions about not eating or drinking for a few hours, which is common when contrast is used.
- Take your usual medicines unless told otherwise, and bring a list of them.
- Remove metal items such as jewellery, glasses, hairclips and clothing with metal fastenings from the area being scanned.
- Allow time for a cannula to be placed if you are having contrast, and arrange how you will get your results.
What happens
You lie on a flat bed that moves through a doughnut-shaped ring (not a closed tunnel). A radiographer operates the scanner from the next room and can see and hear you; you may be asked to hold your breath for a few seconds at times.
If contrast is needed, a small cannula is placed in a vein and the dye is injected during the scan — this often gives a brief warm or flushing feeling and sometimes a metallic taste or the sensation of needing to pass urine, which passes quickly. For some scans the contrast is given as a drink or into the back passage instead.
The scan itself usually takes only a few minutes, though the whole appointment is longer. Afterwards you can normally eat, drink and carry on as usual straight away; a radiologist reviews the images later and sends a report to the doctor who referred you.
Is this scan right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Pregnancy, unless the scan is genuinely needed and cannot wait or be replaced by a radiation-free test.
- When the question is better answered without radiation — for example MRI for soft tissue, brain detail or in younger people, or ultrasound for many abdominal and pelvic questions.
- Asymptomatic people seeking a whole-body CT 'check', where radiation and incidental findings usually outweigh benefit.
- People with severe contrast allergy where contrast is essential, unless managed with specialist input and precautions.
Delay or rearrange if…
- You may be pregnant, until the need and timing have been discussed.
- Your kidney function is reduced or unstable and contrast is planned, until it has been assessed.
- You have an untreated severe allergy to contrast dye, until precautions are arranged.
- Key prior scans or blood results are missing that would change which test is needed.
- You have a treatable acute infection or unstable condition that should be addressed first, unless the scan is urgent.
Alternatives to discuss
- No scan, or watchful waiting, if symptoms are mild and a scan would not change management.
- MRI, which uses no radiation and is better for soft tissue, brain and spine.
- Ultrasound, which uses no radiation and suits many abdominal, pelvic and vascular questions.
- X-ray as a lower-dose first-line test for bones and chest.
- Going through an NHS pathway rather than self-funding, where time allows.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Gives fast, detailed cross-section pictures of bones, the chest, the tummy and pelvis
- Very good at detecting injuries, bleeding, lung problems and many cancers
- Can help diagnose a problem, stage a cancer, plan treatment or guide a procedure
- Quick to perform, which is valuable in emergencies and for people who cannot lie still for long
- A clear result can speed up the right treatment or provide reassurance
Risks & complications
- A brief warm/flushing feeling, metallic taste or a sense of needing to wee when contrast is injected
- Mild nausea or a headache after contrast
- Exposure to a small dose of radiation
- An 'incidental' finding picked up by chance that may be harmless but leads to more tests and worry
- A mild allergic-type reaction to the contrast dye (itching, rash)
- Contrast leaking under the skin at the injection site, causing swelling and discomfort
- A scan that has to be repeated because of movement or technical issues
- A normal scan that gives false reassurance when a problem is present but not visible
- A serious allergic reaction to iodine-based contrast (severe reactions occur in well under 1 in 1,000 people)
- Temporary worsening of kidney function from contrast, usually reversible and more likely with pre-existing kidney problems
- A very small increase in lifetime cancer risk from the radiation, which adds up with repeated scans
The two main considerations with CT are the small radiation dose and the contrast dye. Radiation risk from a single needed scan is small and usually outweighed by the benefit, but it is a reason to avoid unnecessary scans, especially in younger people and with repeated imaging. With contrast, the key issues are kidney function and previous reactions — tell the team about both, and ask whether contrast is really needed.
Published figures to discuss
Radiation dose and risk vary widely by the body part scanned, the equipment, the settings used, and the patient's age (risk is higher in children and lower in older adults). The estimated lifetime cancer risk from a single needed scan is small and is usually outweighed by the benefit of getting the right diagnosis; the concern is mainly repeated or unnecessary scans. Contrast reactions and kidney effects also vary with the dye used and the patient's baseline health.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Estimated extra lifetime cancer risk — CT head | Around 1 in 10,000 (about 2 mSv, roughly a year of natural background radiation) | Risk is higher in children and lower in older adults; a single needed scan's benefit usually outweighs this. | Radiation dose and lifetime cancer risk from common CT examinations — PubMedpubmed.ncbi.nlm.nih.govPublished figure |
| Estimated extra lifetime cancer risk — CT chest or abdomen/pelvis | Roughly 1 in 2,500 (chest) to about 1 in 2,000 (abdomen/pelvis), at typical adult doses | Doses and risks vary by scanner and protocol; repeated scans add up, which is why unnecessary CT is avoided. | Radiation dose and lifetime cancer risk from common CT examinations — PubMedpubmed.ncbi.nlm.nih.govPublished figure |
| Serious allergic reaction to iodine-based contrast | Well under 1 in 1,000 injections | Mild reactions (warmth, flush, nausea) are common and harmless; units are equipped to treat severe reactions. | Radiation dose and lifetime cancer risk from common CT examinations — PubMedpubmed.ncbi.nlm.nih.govPublished figure |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is usually no physical recovery from a CT scan. Most people return to normal activities, work and driving straight away. The main thing you are waiting for is the written report.
- No after-effects at all for most people
- A short-lived warm flush, metallic taste or mild nausea if contrast was used
- Feeling fine to drive and work the same day
- A wait of days to a couple of weeks for the written report, which can feel anxious
Aftercare
- Carry on with normal activities, work and driving — no recovery is usually needed.
- Drink fluids normally if you were given contrast, to help your body clear it.
- Restart metformin or other medicines as advised; sometimes the team gives specific instructions after contrast.
- Watch for any delayed rash, swelling or breathing difficulty after contrast and seek medical advice if it occurs.
- Make a note of when and how you will get your results, and who will explain them.
- Chase the result if you have not heard within the expected time — do not assume no news is good news.
- Ask for a copy of the report and images if you may need them for another opinion.
- Pregnancy status and kidney/diabetes/thyroid history shared with the team
- Any previous contrast reaction reported
- Eating/drinking instructions followed if contrast is planned
- List of your medicines to hand
- Date and route for getting your results
- A named contact if you have questions after the scan
⚠ Get urgent help if…
- Difficulty breathing, wheezing or throat tightness after contrast — call for emergency help
- Widespread rash, hives or swelling of the face, lips or tongue after the scan
- Feeling faint, very unwell or having a racing heart after contrast
- Pain, swelling or spreading redness at the injection site where contrast was given
- Producing much less urine than usual in the days after a contrast scan
- New or rapidly worsening symptoms while you wait for results — seek advice rather than waiting for the report
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your radiologist gives you.
Results & realistic expectations
A good result is a clear set of images that answers the question your doctor asked — whether that is reassurance, an explanation for your symptoms, or information to plan treatment or stage a cancer. The radiologist's report is usually ready within about 1–2 weeks, and sooner if urgent.
A normal scan is reassuring but does not prove you are completely free of disease, because CT cannot show everything and some problems are not visible. The scan also cannot, by itself, tell you what a finding means for you — that needs your doctor to put it together with your symptoms and other tests.
A CT scan is a snapshot in time and can become out of date if your symptoms change or time passes. Because it uses radiation, repeat scans should be done only when they will add useful information. Your doctor will advise whether and when a follow-up scan is needed and weigh it against the small radiation risk.
Related tests, treatments or support
CT is often used alongside other tests — blood tests, an ultrasound, an X-ray, or an MRI — because each answers a different question. A finding on CT may lead to a further targeted scan, a PET-CT, or a biopsy. Your doctor should explain how the pieces fit together rather than ordering tests in isolation.
Follow-up & long-term care
Results are normally sent as a written report to the doctor who referred you, who then explains them and arranges any next steps — reassurance, treatment, a further test, or a specialist referral. Make sure you know who is responsible for giving you the result and by when, and chase it if you have not heard.
Repeat, follow-on and what comes next
- Scans sometimes need to be repeated because of movement or technical issues.
- An unclear finding may need a follow-up scan after an interval, balanced against the radiation dose.
- A finding on CT may lead to a further targeted scan, a PET-CT, or a biopsy to find out what it is.
- Comparing with previous scans often matters — bring or request prior imaging where possible.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- A clear route to your written report and a named person to explain it.
- A plan for any incidental or unclear findings, with sensible thresholds for further tests.
- Contact details for delayed contrast reactions or questions after the scan.
- Your images and report made available to you and any other clinician you choose.
- A record of the radiation dose so future scans can be considered in context.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The body part and number of regions scanned
- Whether contrast (iodine) is used, including the cannula and the dye
- Whether a specialist radiologist reports it and how quickly
- Same-day or urgent reporting versus a standard turnaround
- More complex scans such as CT angiography, cardiac CT or CT colonography
- Any follow-up consultation to explain the results
- Whether further scans or a biopsy are needed if something is found
- The radiographer/facility fee and which body part(s) are included
- Whether contrast is included or charged separately
- The radiologist's reporting fee and the expected turnaround time
- Whether a consultation to explain results is included
- What happens (and what it costs) if the scan is inconclusive or needs repeating
- What happens if an incidental finding needs further tests
- The cancellation and rebooking policy
On the NHS? CT is commonly available on the NHS when a doctor decides it is clinically needed; private scans are mainly used for speed or choice, and a referral is normally still required.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Not mentioning the radiation dose or that the same question might be answered without radiation.
- Not explaining that a normal scan does not rule out every condition.
- Using contrast without checking kidney function or asking about previous reactions.
- Not discussing incidental findings and how they will be handled.
- No clear plan for who gives the result and by when.
Marketing red flags
- Claims that a whole-body CT 'catches everything' or 'prevents cancer'.
- Promoting CT 'health screens' to well people without mentioning radiation and incidental findings.
- Implying a normal scan guarantees you are healthy.
- Adding extra regions or contrast without a clear clinical reason.
- No named clinician to explain results or arrange follow-up.
Choosing a specialist safely
- Check the radiologist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the radiologist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good radiologist will welcome every one of these.
- What specific question is this scan meant to answer for me?
- Will I need contrast, and do my kidneys or diabetes need checking first?
- How much radiation is involved, and is this the lowest-dose test that will answer the question?
- What happens if the scan is normal, abnormal, or shows something unexpected?
- Could MRI or ultrasound answer this without radiation?
- Who will explain my results to me, and by when?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the radiologist who carries out my scan, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this scan not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Can I have a CT scan on the NHS?
Is the radiation from a CT scan dangerous?
Why might I need contrast dye?
Does a CT scan hurt?
How long until I get my results?
Should a well person have a CT body scan for screening?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — CT scan UKHSA / GOV.UK — patient dose information (radiation risks of imaging) Royal College of Radiologists — iodinated contrast media guidance Radiation dose and lifetime cancer risk from common CT examinations — PubMed NICE — guidance and topics on imaging
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
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