CT scanner and image - source Wikipedia

More than 60 million CT scans are performed every year in the United States. A CT scan uses a computer to assemble multiple x-rays taken in rapid sequence to produce a far more detailed image than a conventional x-ray. CT scans are helpful in the diagnosis and management of many medical conditions.

All tests have a risk-benefit ratio. With a CT scan it is important to balance the information the test may or may not yield and how that information might affect the management of your medical condition against the risk of the test. And CT scans have risk. Radiation from x-rays damages DNA, which can cause cancer and for women the radiation can also damage the ovaries. So many CT scans are performed every year in the US it is estimated they cause 1% of cancers in this country. While some doctors argue that estimate is too high, there is no denying that radiation has risks, and whether CT scans cause 0.4% of cancers or 2% of cancers is not really the point. The safest level of radiation is the lowest level of radiation.

The risk of cancer from a CT scan depends on age and the body part scanned; children and young women are at greatest risk. The breasts are especially vulnerable, so a CT scan to the chest carries the greatest risk. The risk of cancer for a women in her 20’s from a chest CT may be as high as 1%. The risk of cancer after a CT scan of the abdomen for a woman in her early 20’s is 1/1000.

Women also have the added risk of radiation damage to the ovaries, potentially affecting fertility. While you can’t shield your ovaries during a scan of your belly, make sure you are given a lead apron to place over your lower belly to protect your ovaries when any other part of your body is x-rayed. It is also important to not be pregnant during a CT scan as high levels of radiation may have consequences for the baby. If you are not using highly reliable contraception and are sexually active, you could be pregnant.

If you are critically ill a CT scan is a powerful tool that may help determine the type of urgent or emergent care that you need. CT scans identify bleeding and infection in the belly, blood clots in the lungs, and bleeding into the brain. There is no doubt CT scans are life saving for thousands of people, and in these situations the benefits far outweighs the risks. CT scans are also very useful for evaluating response of certain cancers to chemotherapy and helping to plan specific surgeries.

However, in evaluating a chronic symptom the benefit of a CT scan should be highly scrutinized. Some experts believe up to 1/3 of CT scans might not be justified (Brenner and Hall, NEJM; 2007). The reason behind all these extra tests isn’t really known, but it is probably a combination of factors: fear of missing something, medico-legal concerns, failure to realize another test without radiation could be used, and patient reassurance. It has also been suggested that doctors who have ownership in the center where the CT scan is performed (or the equipment) are more likely to order a scan.

So if you are sitting in your doctors office talking about a pain you have had for a long time and a CT scan is recommended, think about asking these four questions

  1. What are you specifically looking to find and how will those results affect my treatment? If there is not going to be any effect on treatment, then the test is probably not indicated. Also, if your doctor can’t tell you what they want to find or exclude then you should ask for another option or another doctor. Considering the risks of radiation, it’s hard to justify a fishing trip.
  2. How much radiation does this scan deliver? In my opinion, if an ordering provider doesn’t know that answer, they shouldn’t order the test. Doctor’s should know the benefits AND risks of every test they order.
  3. Is a test without radiation, such as an ultrasound or an MRI, an option?
  4. Do you have any ownership in the center where you have referred me for the scan?
At the end of the day, a CT scan may still be the best test for you, but an informed patient always asks questions and a good doctor will welcome those questions. Because if the test is really needed and the doctor is well informed, the answers to those questions should only take a couple of minutes. 

Join the Conversation


  1. Hello,
    Even if the doctor knows the amount of radiation the CT scan is *supposed* to deliver, that doesn’t really mean anything. The massive overdoses of radiation delivered during CT scans (that have been in the news over the last year – people losing all of their hair after a scan, etc.) reportedly were a result of techs who were not using appropriate settings and medical physicists who allegedly were misinformed by the machines’ manufacturers… as well as miscalibration by either manufacturer reps, or some other personnel. What the scan is supposed to deliver and what it actually delivers can be two entirely different things, unfortunately. I avoid CT scans like the plague and *always* ask for an MRI instead of a CT if it is at all possible. So far, it’s worked 100% of the time.

    1. Excessive doses of radiation from CT scans were reported from perfusion brain scans at several hospitals. Typically, that involves a tech/radiologist not following manufactureres recommendations and developing in house protocols. Miscalibration can happen with any equipment, whether it’s your brakes at the mechanic or a CT scan. Both can have disasterous consequences.

      The bigger point is that many people getting CT scans don’t need them and may not need any imaging. Unfortunately, itis common plave in an American emergency room to get a CT scan before a consult from a general surgeon for suspected appendicitis (or even abdominal pain of any kind). Often a good history and physical can remove the need for a scan.

  2. I just realized after having a cat scan 2 0r 3 months ago, ,could not figure out why my hair all of a sudden was lifeless literally!! ny head hurts on the top, could this be a possibility of too much radiation, and will your hair ever recoup!!

    1. I really think it is. I had 3 cat scans last Nov. and a month later the same happened to my hair. Almost a year later, it is still lifeless, dry and brittle and breaks off at the ends. I use to have shoulder length naturally curly hair. Now it is short (from breakage) straight and lifeless, dry and brittle. To this day, it hasn’t gotten any better. I have spent hundreds of dollars of damage treatments and vitamins to help with this situation but nothing works.

      1. Hi Toni … Same happened to me after a long stay in the hospital (and multiple CT scans) this past Jan/Feb. Now approx. 9 months later and my hair is still dry, brittle, lifeless. I’m wondering (fingers crossed you’ll even read this) if you can let me know how your hair is fairing now, 2 years later.

  3. I wonder if the author is still following this and leaving comments. I may be a patient who is considering an unneeded CT scan, and in my case, I am concerned about this. My husband and I want to try to get pregnant in the next month or two, but were going to wait until just after I get my CT scan. Now I’m thinking (if I even get it) should we wait longer to try? Or am I one of those patients who shouldn’t be getting a CT scan in the first place…

    I think I pushed my doctor into ordering the scan. I have had a pain in my upper left quadrant. It developed a few months after my daughter was born (she is 10 months old). It got worse, and a lump formed there. At night, it was uncomfortable. I could never palpate a mass, and it was in a weird place away from lymph nodes (around my ribs) so I brushed it off. At some point, the pain and lump became too much to ignore as the pain and weird sensation of having something there in my side made it hard to sleep. I thought I should make a dr’s appointment, but was worried I’d be blown off as a neurotic worrier, so didn’t. Then I lost a whole bunch of weight, suddenly. About 2 months ago, I stopped breastfeeding and I was still around 130 pounds (10 pounds heavier than my normal weight of 120 that I have consistently held for years… only time it dipped was when I was extremely ill years ago). Now I weigh 115. I have tried doing some “big mac” therapy, eating a lot (no problem since it’s the holidays) – did not stop losing weight. My dr ordered an ultrasound and they found a small amount of free fluid in ULQ. They couldn’t find any suspicious lymph nodes in my abdomen, all my organs (pancreas, spleen, liver, kidneys) looked good – not inflamed, no suspicious spots. I had a normal CBC, thyroid levels normal. At this point, my doctor wrote off my weight loss to a high metabolism, and said he wasn’t worried about the free fluid – even though I reiterated the pain and discomfort it caused me was enough to keep me awake at night. So he said he would order the CT scan and said to see a GI specialist…. but again, I feel like those recommendations were made to appease me and he basically said he was more worried about me being worried about it.

    Now, it’s been about a week and a half since I saw him, and I noticed that with the beginning of my cycle, the lump and the pain reduced. Even though it is in an unlikely spot, the doctor said that it could be due to endometriosis (which I have). I’m approaching ovulation now, and it feels like the lump and pain are returning.

    Considering all this, I am thinking about calling him back and not having the CT scan done as I don’t want to chance hurting my ovaries for nothing. But then I get worried as I am from an area of high cancer rates in young people due to dumping of carcinogenic waste. One of my classmates just died from cancer (she was in her 20s), and including her, I know of 5 people my age who got cancer (2 leukemias, colon cancer – the one who died, testicular, and ovarian). Couple that with the weird weight loss and fluid hanging out where it shouldn’t and I get nervous. I’m also *still* battling thrush, which I understand is not normal. Even after two rounds of diflucan, and months of lotramin and nystatine (sp), huge doses of probiotics, I cannot get rid of it. There is even some in my mouth.

    To scan or not to scan?

    1. RB, did they ever figure out what caused that pain in your left side? I’m experiencing the same symptoms and drs are still scratching their heads. They did a ct scan on me yesterday because they thought I may have a ruptured spleen. But they found nothing so now I regret having that done after reading this thread. I also would like to try getting pregnant ASAP due to age so am very concerned of the ct scan will affect my fertility. Please let me know if you have any information on whether they were able to figure out what caused the pain and if you ended up doing the scan, what did the doctor say about fertility? Thank you

    2. After an Ultrasound found an Abdominal Aortic Any. in 2013, I had the 1st Cscan with injection to verify its’ size which was 4.3 c. Another six months later, and another six months later. In early 2014 after another Cscan with injection the any. was large enough to operate and place Stent over it (end of Sept. 2014). The Doctor again did a Cscan to verify the stent placement. Immediately following surgery as I woke up, I had extreme lower back pain as well as I started to have strands of hair falling out. Since the operation, I have had Cscans every three months to verify stent is in place and have been told I will have one more in three months and every year after that. All with injection of radioactive fluid.
      My hair is still falling out – and the back pain (although not quite as severe) has remained with pain pills the only way of relieving the pain. The Doctor also ordered X-rays due to the back pain, to no avail.
      This is extremely upsetting since before operation I never had back pain, nor did I have a problem of losing hair.
      The only logical explanation (common sense) tells me that the Cscans did something to my body thus pain and hair loss.
      although I realize the AAA was nothing to mess with (death if not done) couldn’t there of been another type of tests done rather than the constant exposure to radiation???????

  4. I’m 14 weeks pregnant with twins and received a ct scan and an X-ray to check for a blood. Clot in my lung which I couldn’t understand how they came to think i had one and I was not informed of the risks or of the fact that they were injecting me with radiation for the scan and now I’m really worried after reading this and others comments n online, what should I do iv in feeling sick ever since I came. Home?

  5. hello
    My wife in 6.5 week pregnancy. because of an accident we had a ct scan of her brain.
    so i want to know is there any risk of radiation for baby.
    and what i have to do in that condition.
    kindly advise..

  6. The doses in cat scans are low the eqivilent of a commercial air flight so there is not much damage will be done I’ve had two cat scans and 70 xrays and I have a microscope my sperm count was normal. sperm multiples faster than eggs and radiation attacks fast multiplying cells but you may see some let me say SOME low counts in multiplying cells for about three weeks to three months but u will not be permanently sterile beck in 1950s they took multiple xrays on pregnant women’s without miscarage or birth defects. But basically if you take a lot of ct scans it can cause permanent hair loss but sex cells repair themselves over time.

    1. Jessie, the amount of radiation from a CT scan is NOT equivalent to the that from a transatlantic flight. It can range from 80 to 100 times that of a flight. Here is a comparative table for guidance. https://www.gov.uk/government/publications/ionising-radiation-dose-comparisons/ionising-radiation-dose-comparisons

      While males produce sperm through out their lives, females are born with a set number of eggs and if these are damaged by radiation at any stage, they will remain damaged. Perhaps not all eggs will suffer damage, perhaps none will; the point is women do not produce new sex cells.

  7. I had a CT scan done 2 months ago for irregular periods. I’m 47 and had been spotting in between periods for quite awhile, and having a period roughly every 3 weeks. So my ob/gyn ordered a CT scan after an ultrasound revealed some ovarian cysts. I guess she wanted to get a better handle on what type of cysts they were, idk. In fact when I went in for the CT test, I was on my period. But since then, I haven’t had a period nor even any spotting. Nothing. And this was 2 months ago last week. I’m wondering if a CT scan can cause me to stop having periods?! Pregnancy is not a possibility so idk what else it could be.

  8. How about for women who have already had a abdominal/pelvic CT scan. Can the eggs repair themselves? How long does it take for the ovaries/eggs to repair? Is there anything a woman can do (diet, supplements) to undue the damage?

  9. Ive been in two times xray this month. I’m wondering if a Chest xray can cause me to stop having periods? I still dont have periods by now. Im 22

  10. I have had 3 scan last year and one this year due to abdominal pain , im 28 years old , i think its too much

  11. My son is 29 he had kidney stone two times they did a CT scan in the term of 2 years .I am concerned if he wants to have children. How can he stop this hopping so often. Thank you.

  12. can a cat scan interfere with HRT? Since my ct scan 15 days ago (I am 70 Yrs old on HRT since I was 48 yrs) I have had daily headaches and spotting. Today I had a very large gush of blood and have been feeling like bad PMS.

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