A bone scan helps find cancer that has started in or has spread to the bones. In addition, a bone scan can help monitor how well treatment is working for cancer in the bone.
How does a bone scan work?
A bone scan is a nuclear medicine test. This means that the procedure uses a very small amount of a radioactive substance, called a tracer. The tracer is injected into a vein. Areas where too much or too little tracer has been absorbed by the body may indicate cancer.
Usually the entire body is scanned during this procedure. If the results show bone damage that may be caused by cancer, more tests may be needed. These tests may include a computed tomography (CT) scan , a positron-emission tomography (PET) scan , magnetic resonance imaging (MRI) , or a biopsy .
Who does my bone scan?
A specially trained and certified nuclear medicine technologist performs the test. The technologist is supervised by a radiologist or a nuclear medicine physician. A radiologist is a medical doctor who specializes in using imaging tests to diagnose disease. A nuclear medicine physician is a medical doctor who specializes in using tracers to diagnose and treat disease. The radiologist or nuclear medicine physician interprets the scan results.
Facilities that provide bone scans include the following:
The radiology or nuclear medicine department of a hospital
An outpatient imaging center
Getting ready for a bone scan
Usually, you do not need special preparations before a bone scan. For example, you can eat and drink normally before your appointment.
However, tell your doctor about all medications you take. Medicines that contain barium or bismuth can affect the test results. As a result, your doctor may recommend not taking them before your scan.
Also mention drug allergies or other medical conditions you may have. And women should tell their doctors if they are breastfeeding or if there is any chance they are pregnant.
Additionally, check with your insurance provider in advance. Find out whether the cost of the test will be covered and whether you need to pay part of it.
Once you arrive for your scan, you will be asked to sign a consent form. The consent form states that you understand the benefits and risks of the bone scan and agree to have the test. Talk with your doctor about any concerns you may have about the bone scan.
Before the test, you will remove jewelry and any other metal objects. You may also need to change into a hospital gown.
During the procedure
First, a tracer will be injected into your body through a vein in your arm. The injection may sting a little bit. But you will not feel the tracer move through your body. It takes 1 to 4 hours for your bones to absorb the tracer.
While you wait, you will drink several glasses of water. By urinating frequently, you will remove radioactive material that has not collected in your bones. During this time, you are not dangerous to others. The amount of radioactivity in your body is less than the amount from a normal x-ray.
Next, you will lie on your back on an exam table. The technologist will position a large scanning camera above your body. You will need to remain still to prevent blurry pictures.
During the scan, the camera will move slowly around your body. It takes pictures of the tracer in your bones. The technologist may ask you to change positions during the scan to get pictures from different angles.
A whole-body scan takes about 1 hour to complete. Although the scan is not painful, you may find lying still uncomfortable.
After the procedure
After your bone scan, you may return to your usual activities. This includes driving.
You should not feel any side effects from the tracer or the test itself. However, your doctor may ask you to drink lots of water for the next 24 to 48 hours. This flushes out any tracer that may be left in your body. Typically, all of the radioactive material is gone after 2 days.
If you notice pain, redness, or swelling around the injection site in your arm, call your doctor immediately.
Questions to ask your doctor
Before having a bone scan, consider asking the following questions:
Who will perform the bone scan?
Is the radiologist or nuclear medicine physician board-certified?
Is the facility accredited by the American College of Radiology  to perform bone scans?
What will happen during the bone scan?
How long will the procedure take?
What are the risks and benefits of having a bone scan?
How accurately can a bone scan find cancer?
When and how will I learn the results?
Who will explain the results to me?
What other tests will I need if the bone scan finds evidence of cancer?
Bone Cancer 
RadiologyInfo.org: General Nuclear Medicine 
National Library of Medicine: Bone Scan