Radiation Therapy: What It Is and What to Expect
Medically reviewed by Sumiran Racherla, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor provides Radiation Therapy?
A radiation oncologist, a doctor who uses radiation to treat cancer, provides radiation therapy. A radiation therapist works with the oncologist to figure out your treatment area. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What it is
Radiation therapy uses high-powered radiation, particles, or radioactive seeds to kill cancer cells. Radiation harms quickly growing cells most, so it harms cancer cells more than normal cells. Doctors use it to fight many types of cancer. The sections below focus on cancer treatment.
Types of radiation therapy include external and internal. External radiation is the most common form. A machine aims radiation at the tumor from outside the body. Internal radiation is placed inside your body. One kind uses radioactive seeds placed in or near the tumor.
Why a doctor might recommend it
Sometimes radiation is the only treatment you need. It may also be used with surgery or chemotherapy to do the following.
- Shrink a tumor as much as possible before surgery.
- Help prevent the cancer from coming back after surgery or chemotherapy.
- Relieve symptoms caused by a tumor, such as pain or pressure.
- Treat cancers that cannot be removed with surgery.
How to prepare
Before treatment starts, you meet with your doctor or nurse for 1 to 2 hours. Next comes a planning session called a simulation. During it, you may have the following.
- The radiation therapist uses tattoos or small dots of ink to mark the treatment area on your skin.
- A body mold is a plastic or plaster form that keeps you still.
- For the head and neck, you may be fitted for a mask.
Wear soft, comfortable clothes, such as fleece or cotton.
What happens during it
You lie on a treatment table or sit in a special chair. You need to stay very still so the radiation goes to the same place each time. You get radiation for 1 to 5 minutes. You can breathe normally. The radiation therapist leaves the room just before treatment begins. Tell the therapist if you feel sick or uncomfortable.
Recovery
Treatment is usually at a clinic or radiation therapy center. Damaged healthy cells usually recover within a few months after treatment ends. External beam radiation therapy will not make you radioactive.
Call 911 or go to the emergency room if you have bleeding that will not stop, trouble breathing, chest pain or discomfort lasting two minutes or more, or fainting.
Risks and side effects
Radiation can also affect nearby healthy cells. This can cause side effects. Many people who get radiation therapy have fatigue. Fatigue means feeling exhausted and worn out. Other side effects depend on the part of the body that is treated. Radiation from outside may cause skin changes, such as hair loss, red or burning skin, or thin skin. Some side effects show up months or years after treatment. These are called late effects. Ask your doctor or nurse which late effects you should watch for.
Who performs it
A radiation oncologist and a radiation therapist plan your treatment area together.
Common questions
Can you feel the radiation?
No, you will not be able to feel, hear, see, or smell the radiation.
Will radiation from a machine make me radioactive?
No, radiation from a machine will not make you radioactive. You may safely be around other people, even pregnant women, babies, and young children.
How often is radiation given?
Most people have treatment once a day, five days a week, Monday through Friday. The number of weeks depends on the type of cancer, the goal of treatment, the dose, and the schedule.
How does a direct primary care or concierge doctor fit in?
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
Sources
- MedlinePlus - Radiation therapy
- National Cancer Institute - External Beam Radiation Therapy for Cancer
- National Cancer Institute - Radiation Therapy Side Effects
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
