Medically Reviewed on 5/27/2022

Things to know about X-rays

X-ray of herniated disc between L4 and L5
X-ray of herniated disc between L4 and L5.
  • X-rays are a form of electromagnetic radiation that can pass through solid objects, including the body. X-rays penetrate different objects more or less according to their density. In medicine, X-rays are used to view images of the bones and other structures in the body.
  • X-rays were first discovered by Wilhelm Conrad Roentgen, a German physics professor. Roentgen also studied X-rays and their ability to pass through human tissues to produce images of the bones and metals visible on developed film.
  • To obtain an X-ray image of a part of the body, a patient is positioned so the part of the body being X-rayed is between the source of the X-ray and an X-ray detector. As the X-rays pass through the body, images appear in shades of black and white, depending on the type of tissue the X-rays pass through.
  • For example, the calcium in your bones makes them denser, so they absorb more radiation and appear white on X-rays. Thus when a bone is broken (fractured), the fracture line will appear as a dark area within the lighter bone on an X-ray film.
  • Less dense tissue such as muscle or fat absorbs less, and these structures appear in shades of gray on X-ray film. Air absorbs little of the X-rays, so the lungs and any air-filled cavities appear black on an X-ray film. If pneumonia or tumors are present in the lungs, they are denser than the air-filled areas of the lungs and they will appear as whiter spots on X-ray film.

What are uses of X-rays?

The most common form of X-ray used is X-ray radiography, which can be used to help detect or diagnose:

Is it safe to have X-rays while pregnant or breastfeeding?

The risk of side effects of an X-ray while you are pregnant is extremely minimal, but it is always important to protect the developing fetus from harm. You should always tell your healthcare professional if you are or think you may be pregnant if an X-ray exam is prescribed.

X-ray examinations of areas of the body including the arms, legs, chest, head, or teeth do not expose your reproductive organs or your unborn child to a direct X-ray beam. X-rays of the abdomen, stomach, kidneys, lower back, or pelvis can potentially expose an unborn child to the direct X-ray beam. Depending on your condition and the area that needs to be X-rayed, your doctor may cancel or postpone your X-ray exam if you are pregnant. The X-ray exam also may be modified to reduce the radiation. Often the risk of not having a necessary X-ray can be greater than the risk of the radiation.

It is safe to have X-ray tests while breastfeeding. The radiation does not affect the milk or the baby, and breastfeeding is safe after a regular X-ray. Mammograms may be more difficult to read in a lactating mother, but women who are breastfeeding can continue to do so even if they need a mammogram. In the case of X-rays used with contrast media, it is safe to breastfeed as long as there is no radioactive isotope used in the contrast. If there is a radioactive isotope used, your doctor may recommend you stop breastfeeding for a short time. Ask your doctor about the contrast agent used and let them know that if you are breastfeeding.

What are the types of X-rays?

There are many types of X-rays that are used to diagnose conditions and diseases. The following are examples:

  • Mammography is a type of X-ray radiograph that is used to detect breast cancer.
  • Computed tomography (CT) scans combine X-ray with computer processing to create detailed pictures (scans) of cross-sections of the body that are combined to form a three-dimensional X-ray image.
  • Fluoroscopy uses X-rays and a fluorescent screen to study moving or real-time structures in the body, such as viewing the heart beating. It can also be used in combination with swallowed or injected contrast agents to view the digestive processes or blood flow. Cardiac angioplasty uses fluoroscopy with a contrast agent to guide an internally threaded catheter to help open clogged arteries. Fluoroscopy is also used to precisely place instruments in certain locations within the body, such as during epidural injections or joint aspirations.
  • Other uses for X-rays and other types of radiation include cancer treatment. High-energy radiation in much higher doses than what is used for X-ray imaging may be utilized to help destroy cancerous cells and tumors by damaging their DNA.


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What are the dangers and risks of X-rays?

Radiation does have some risks to consider, but it is also important to remember X-rays can help detect disease or injury at early stages so the ailment can be treated appropriately. Sometimes X-ray testing can be life-saving.

The risk from X-rays comes from the radiation they produce, which can harm living tissues. This risk is relatively small, but it increases with cumulative exposure. That is, the more you are exposed to radiation over your lifetime, the higher your risk of harm from the radiation.

There is a slightly increased risk of developing cancer later in life after X-ray exposure. X-rays have also been linked to cataracts in the eyes and skin burns, but only at extremely high levels of radiation.

Things that are risk factors for X-ray damage include:

  • A higher number of X-ray exams
  • Receiving X-rays at a younger age
  • Being female (women have a slightly higher lifetime risk than men for developing radiation-associated cancer)

Things you can do to reduce radiation risks from X-rays:

  • Keep track of your X-ray history and make sure your doctors are aware of it
  • Ask your healthcare professional if there are alternative tests to X-ray exams
  • If you are pregnant or think you may be pregnant, tell the X-ray technician or radiologist

How do I prepare for an X-ray exam?

There is no special preparation needed for a regular diagnostic X-ray. You may be asked to strip down and wear a hospital gown, or at least remove clothing on the part of the body that needs to be X-rayed. You may be asked to remove any metal objects such as eyeglasses, jewelry, or watches that may interfere. If you are getting an X-ray with contrast such as barium or iodine, you may be given a liquid to swallow, an injection, or an enema with the agent before the X-ray. If you are getting an X-ray of your gastrointestinal tract you may be told not to eat or drink anything for 8 or more hours before the procedure so your stomach is empty. Your doctor will tell you if you need to do this.

An X-ray technician will position you on an exam table and give instructions on how you should position your body for the X-ray. You can ask questions if you have them.

How do medical professionals perform an X-ray?

The X-ray test works by positioning the part of the body being X-rayed between the source of the X-ray and an X-ray detector (such as a film). You usually will need to lie on a table or stand against a flat surface to ensure your body is in the right place for the X-rays to pass through the body part being examined. You will be asked to stay still so the image will be as clear as possible. This will provide the most accurate image. Dental X-rays usually involve biting on a piece of film.

A radiology technician will aim the X-ray machine at the body part that needs to be X-rayed, and then they will leave the room or go behind a screen to turn on the machine. The actual X-ray usually only takes a fraction of a second, and you will not feel anything when it occurs.

The radiology technician may return and reposition your body or the X-ray slide to take additional X-rays from multiple angles.

The entire procedure for a regular usually only takes a few minutes. If contrast agents are used, a procedure may take an hour or more.

What are the side effects of contrast agents?

If contrast agents are used, you may experience some side effects.

Side effects of barium include:

Side effects of iodine include:

What happens after the X-ray procedure?

There are no side effects or after-effects of a regular X-ray and you should be able to return to your normal daily activities immediately.

If you had an X-ray with contrast, there may be some temporary side effects. Barium may cause your stool to turn a whitish color, and iodine injections may cause some people to feel sick or develop a rash. Injections given to relax the stomach before an X-ray of that body part may cause temporary blurred vision. You will likely be instructed to drink plenty of fluids after an X-ray with contrast to help your body rid itself of these agents.

When and how will I receive the results of my X-rays?

After an X-ray is taken, the image is produced immediately. However, the time it takes to learn the results varies.

If your X-ray is taken in a doctor's or dentist's office, the doctor or dentist will likely read the X-ray and discuss the results with you in the same visit. If your X-ray is taken while you are in a hospital's emergency department, or as an in-patient in a hospital it will be read by the emergency physician or sent to a radiologist to read. Depending on how busy the hospital is, this can take a few hours. Once read, it will be sent to the physician treating you, who will discuss the findings.

Sometimes, you may be sent to an imaging center to have your X-rays taken. Once the X-rays are done, they will be read by a radiologist on staff at the imaging center, and then transmitted to your doctor who ordered the tests. This may take a day or more. Once your doctor receives the results, they will likely call you to discuss the results over the phone or suggest a follow-up visit in the office, or they may refer you to another doctor depending on the findings.

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Medically Reviewed on 5/27/2022
United States Environmental Protection Agency. "Radiation: Facts, Risks, and Realities. April 2012.

Holmes, E.B. "Ionizing Radiation and Medical Imaging." Medscape. Dec. 6, 2019. <http://emedicine.medscape.com/article/1464228-overview>.