While nuclear stress tests are considered safe, some precautions need to be followed both during and after the test.

If you or a doctor suspects you might have an undiagnosed heart condition, they may recommend a nuclear stress test as a diagnostic tool.

During this test, a healthcare professional injects you with a radioactive chemical called a tracer. A technician then uses a specialized camera to take pictures of the tracer as your heart tissue absorbs it. This will be done while you’re at rest and again with your heart rate elevated.

Doctors can use these results to find evidence of a previous heart attack or to diagnose conditions like coronary artery disease.

Let’s take a detailed look at the precautions doctors recommend you take during and after the test.

Before the test, let the healthcare professional know what medications, including over-the-counter (OTC) supplements and herbal remedies, you’re currently taking. Also, mention if you have any known medication allergies.

If you are or might be pregnant or are nursing, let a healthcare professional know. While you may be able to have the test if you are nursing, healthcare professionals may recommend another monitoring method if you are pregnant. Nuclear stress tests are not recommended for people who are pregnant.

Leading up to your test, follow all instructions regarding food, liquid, and medication restrictions. These may include:

  • avoiding caffeine for at least 12 hours
  • avoiding tobacco products for at least 8 hours
  • fasting for 4 hours

Depending on the type of test, you may need to stop taking certain medications if a healthcare professional tells you to. These may include:

  • Regadenoson stress test: A healthcare professional may tell you to avoid medications such as nitroglycerin, theophylline, isosorbide, and PDE-t inhibitors.
  • Dobutamine stress test: You may need to avoid beta-blockers and vasodilators for this test.

If your test includes an exercise component, be sure to wear comfortable shoes to your appointment.

Bring a list of all your medications to your appointment, along with your identification and insurance information.

If you feel unusual during the test, let the technician or doctor know.

After the test, the doctor will give you specific instructions about what you may and may not do. These will vary based on the specific radioactive tracer you were given and the amount used.

While this test’s small amount of radiation exposure is considered safe, your body may remain slightly radioactive for hours to days. Drinking plenty of water can help flush your body of radioactivity. Aim to drink six to eight 8-ounce glasses of water in the 24 hours after your test.

You may want to take a shower and then wash your hands regularly. Depending on the type of tracer, you may be advised to avoid contact with young children, babies, and pregnant people for the remainder of the day to a few days. There are no restrictions on being around older children, adults, and pets.

If you’re nursing, you’ll need to throw away one or several feedings’ worth of milk or freeze it until it becomes safe. A doctor can provide detailed instructions specific to your test.

Most people can resume their usual daily activities immediately after the test. Depending on your test results, the doctor might advise you to limit certain physical activity or avoid certain foods or medications.

Side effects of nuclear stress tests are usually mild and may include:

More serious side effects are rare but could include an allergic reaction to the radioactive tracer. Symptoms of an allergic reaction to a radioactive tracer commonly include:

  • skin rash
  • itching
  • vomiting

However, severe reactions are possible.

When a side effect is an emergency

If you experience server or concerning symptoms, such as those of anaphylactic shock, a rare but emergency allergic reaction, contact 911 or your local emergency medical services. Symptoms may include:

  • difficulty breathing
  • chest pain
  • swelling of your face, throat, or airways
  • hives
  • rapid heartbeat
  • wheezing
  • confusion

The radioactive tracers most commonly used are thallium-201 (Tl-201) and technetium-99 (Tc-99).

Tl-201 decays more slowly than Tc-99. The amount of Tl-201 goes down by half every 3 days, while Tc-99 goes down by half every 6 hours.

At the same time, your body is constantly filtering out these chemicals and removing them through your urine and stool.

The tracer will usually be gone from your body within 1 or 2 days.

Nuclear stress test radiation risk to others

The risk to others is low, but it’s not zero.

For this reason, a healthcare professional may recommend you avoid close contact with young children, babies, and pregnant people for 1 to 2 days after the test. The time the tracer stays in your body can vary by the specific tracer, so it’s best to ask about your specific circumstances.

Frequent handwashing can help prevent the spread of radioactive particles.

Nuclear stress tests have minimal symptoms and side effects associated with them.

During the test, stress is usually brought on through exercise, but medications may also be used to cause stress. When stress is caused chemically with medication, there tend to be more side effects, but they’re usually still mild and short-lasting.

If your symptoms worsen after the test instead of improving, contact a doctor.

Abnormal results could indicate several things, including a previous heart attack, heart damage, or heart disease like coronary artery disease (CAD).

If blood flow is blocked in some parts of your heart, you may need to avoid certain activities, foods, or medications. You might start taking new medications, or in some cases, require surgery.

Depending on the results, a doctor might want to perform additional diagnostic tests, such as cardiac catheterization, a procedure to examine the heart’s blood vessels.

The following includes commonly asked questions about nuclear stress tests.

Most people are exposed to about 3 millisieverts (a measurement of radiation absorbed by the body) of radiation over the course of a year. During a nuclear stress test, you can expect to be exposed to somewhere between 3 and 22 millisieverts of radiation, depending on the tracer used.

This is usually limited to your own body, and you’re only minimally radioactive for a period of 1 to 2 days after the test.

Avoid close contact with children, babies, and people who are pregnant for 1 to 2 days after the test. Follow the doctor’s guidance on any restrictions related to food, medication, or exercise.

Some people can drink coffee after a nuclear stress test, but others might need to avoid caffeine, which can include coffee, tea, chocolate, and other foods and beverages, for 12 to 24 hours. Ask the doctor if you can have caffeine and how soon.

After exerting your cardiovascular system, you may feel tired. You can expect to feel back to your normal level of restfulness after a night’s sleep.

There are no specific risks for older adults getting a nuclear stress test. The level of stress you experience will be determined by your age, health, and ability level.

A nuclear stress test should be avoided for people who are or might be pregnant. If there’s a possibility you’re pregnant, let the doctor know before getting a nuclear stress test.

If you’re nursing, you can have a nuclear stress test, but still let the doctor know. You’ll need to follow special instructions after the test before resuming nursing.

Nuclear stress tests involve having a radioactive tracer injected into your bloodstream. The tracer decays on its own over time, and your body removes it through your urine and stool.

A doctor typically gives you specific instructions regarding what foods, medications, and activities you should avoid both before and after the test.

For 1 to 2 days after the test, you may need to avoid close contact with young children, babies, and pregnant people, and you should wash your hands regularly.