How Long Does Radiation Stay in Your Body After Treatment?

Along with surgery and chemotherapy, radiation therapy has long been a mainstay of cancer treatment. It uses high-energy waves or particles such as x-rays, gamma rays, electrons, or protons to destroy or damage tumor cells. Radiation creates small breaks within the DNA of cancer cells, preventing the cells from growing and dividing, and often causing them to die.

radiation therapy, radiation oncology
Radiation therapy uses high-energy waves or particles to destroy or damage tumor cells.

Because cancer cells divide rapidly, they’re more likely to succumb to DNA damage, but radiation can damage DNA in normal cells as well. The damage that radiation therapy does to normal cells may lead to a variety of side effects, which generally improve over time. These can include fatigue, red or irritated skin the treatment area, and, in rare cases, low white blood cell or platelet counts.

How long does radiation last in the body?

External radiation therapy – a form of treatment that uses a machine to beam high-energy rays into a tumor – affects cells for only a few seconds. The beams pass quickly through the body and are absorbed by special shields positioned around the patient.

Some cancers are treated with internal radiation therapy, in which radioactive material, sealed in a container, is implanted next to or inside a tumor. High doses of internal radiation therapy are given by placing a powerful source of radioactivity in the body for a few minutes at a time. Lower doses are delivered with implants that remain in the body longer, often a few days. In a treatment known as brachytherapy, doctors implant small radioactive pellets, or “seeds,” that emit radiation for a few weeks or months but remain in the body permanently.

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Internal radiation therapy can cause the body to give off small amounts of radiation for a short period of time. Patients who receive temporary implants often stay in the hospital while the implant is in place and may have limitations on visitors. Their bodily fluids are not radioactive. Once the implant is removed, their body is radiation-free.

Patients with permanent implants give off small doses of radiation as long as the radiation source is active – usually a few weeks or months. As with patients receiving temporary implants, the body fluids and personal items of patients with permanent implants are not radioactive. Because it is low-level, the radiation usually doesn’t travel much beyond the area being treated, so there’s little chance of exposing others to radiation. Still, to be on the safe side, patients may be advised to limit contact with small children and pregnant women.

10 thoughts on “How Long Does Radiation Stay in Your Body After Treatment?”

  1. This doesn’t talk about the type of radiation given to thyroid cancer patients – where their bodily fluids are radioactive during treatment. Don’t omit the Thyca survivor.

  2. Dana, Is this article about radiation given currently?
    If not I strongly disagree with this article.
    I had radiation in 1983 and am affected by the radiation I received. I have radiation fibrosis, heart damage ( cardiomyopathy, pulmonary hypertension, all of my valves in my heart are leaky and enlarged left ventricle) and a few other physical problems caused by the radiation all of those years ago. It stayed in my body and slowly worked on my good cells throughout the years.
    Don’t get me wrong. I would have been dead without the radiation treatment. But I do want you to recognize that radiation does hang around in your body after treatment. At least it remained in my body at the dosage I received.

  3. In Feb of 1999 i had six shots of radiation around the site of my melonoma. Just curious if this may have had anything to do with tooth loss down the road. I never had any chemo.

  4. Thanks for your question. Without knowing your complete oral health and medical history, it’s hard to provide a direct answer about what might have caused your tooth loss. High-dose radiation therapy to the head and neck area can cause side effects such as increasing the risk for gum disease and dry mouth. Radiation can also decrease the blood supply to the bones of the head and tissue of the neck during treatment, which can result in slow healing from infection or trauma. To prevent infection and tooth decay, it is very important to see a dentist early in treatment and practice good oral health cleaning habits every day.

  5. I had 30 doses of external radiation . why do I sometimes feel pain in my legs . is this the effects of the treatment

  6. Dear Fran,

    Thank you for your question. Radiation given to a limited area of the body rarely has a substantial or long-lasting effect on the immune system as a whole. The bone marrow in the treated area may decrease in its ability to produce new blood cells, including those that are vital for a well-functioning immune system, but bone marrow outside the treated area should be sufficient to maintain a healthy immune system unless a very large area of the body is treated or there are other underlying issues.

    We hope this is helpful and wish you all the best.

  7. Dear Harold,

    Thank you for your comment, and sorry to hear of your medical troubles. If you received radiation therapy to the leg it can cause discomfort in the treated leg, but if radiation was given to another part of the body, such as the chest, it is unlikely that pain in the legs is related to your treatment. Aside from fatigue, radiation therapy does not typically cause symptoms outside the treated area. Pain in the legs may be due to many different causes and should be discussed with your doctor.

    We hope this is helpful and wish you all the best.

  8. Since having undergone radiation therapy to treat postate cancer a few months ago, i’ve noticed that any littlle scratch or cut i get, i bleed a lot. Also, a little bump causes a funny looking bruise. Not black and blue, but a strange large mark. Can the radiation cause these symptoms.

    • Hi Robert,

      I’m sorry to hear about your health trouble. Unfortunately, we cannot give out medical advice over this blog and would recommend speaking to your doctor about any symptoms or concerns you have.

      Wishing you all the best.


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