During a nuclear stress test, you’ll be injected with a radioactive dye called a tracer. Some of this tracer will remain in your system for a time after the test.

A nuclear stress test is a type of imaging test used to examine your heart.

During a typical stress test, an electrocardiogram (EKG) machine will be used to monitor your heart while it’s at rest and under stress. Stress will be caused either by exercise (an exercise stress test) or by medication (a chemical stress test).

A specialized camera will take pictures of the tracer in your heart both at rest and under stress. These images can be used to diagnose coronary artery disease (CAD) or find evidence of a previous heart attack.

This procedure might also be called:

After the test is complete, you’ll still have some of the radioactive tracer in your body. Let’s take a look at what this means for you.

There are several radioactive tracers that can be administered during a nuclear stress test.

The two most common tracers are thallium-201 (Tl-201) and technetium-99 (Tc-99, or 99mTc). There are two main versions of Tc-99 that might be used, though they’re very similar:

  • technetium sestamibi
  • technetium tetrofosmin

All of these tracers will naturally exit your body through urine and stool. The tracer will usually be gone on its own within a few hours or days.

You can encourage this process to go faster by making sure to stay well hydrated after your nuclear stress test. Everyone is a little different, but people generally need to drink about 2 liters of water every day.

Radioactive tracer goes away in two different ways.

First, the tracer undergoes a natural process called radioactive decay. These tracers are unstable by design, and as time passes, the elements decay into different elements until they’re no longer radioactive.

The amount of time it takes for half of a radioactive tracer to decay is called its half-life. Tl-201 has a half-life of about 3 days, whereas Tc-99 has a half-life of about 6 hours.

Second, the tracers are filtered by your body and exit through your urine or stool.

Some tracers will effectively be gone within a few hours, while others might be detectable in trace amounts for several weeks. A doctor can help you know what to expect based on the specific tracer that you receive.

The amount of radiation you receive during a nuclear stress test is considered safe. After the test, your body will give off a small amount of radiation for a short period of time.

Regular handwashing can help decrease how much radiation exposure the people around you receive. Taking a shower may also help.

It’s generally recommended you avoid close interaction with children and babies for 1 to 2 days after a nuclear stress test.

If you are nursing, plan to save and freeze extra milk leading up to the test. After the test, continue to pump to maintain lactation, but either throw out the milk or freeze it for 30 days to allow enough half-lives to pass for the milk to stop being radioactive.

Normal nursing can resume after 4 days. If you have concerns, the facility that performed the test can usually test the safety of a milk sample as well.

Nuclear stress tests are generally considered safe. Side effects are more common if stress is caused chemically instead of through exercise. Side effects might include:

Severe side effects are rare but might include having an irregular heartbeat or having an allergic reaction to the tracer.

Headache after a nuclear stress test

You might have a small headache after a nuclear stress test. This could be caused by the intensity of the exercise, fasting before the test, or a response to chemicals used in the test. This side effect normally goes away on its own after a short period of time.

Diarrhea after nuclear stress test

Diarrhea isn’t common after a nuclear stress test, though gastrointestinal discomfort can occur if the stress was caused chemically. If you have diarrhea, let a doctor know.

Most people are able to resume normal activity immediately after a nuclear stress test. If you’re not able to do this and the doctor didn’t specifically prepare you for it, then it’s important to contact the doctor.

Always feel empowered to call a doctor if you have any questions after the test that you think of later.

Medical emergency

If you experience severe symptoms like chest pain or difficulty breathing, it could be a medical emergency and you should call 911 or local emergency medical services or go to the nearest emergency room right away.

You may still have other questions about nuclear stress tests. Here are some common questions and answers:

How long are you radioactive after a nuclear stress test?

Tc-99 will usually pass from your system within a few hours to a few days. Tl-201 usually lasts a little longer, passing within a few days to a week.

Can you drink caffeine after a nuclear stress test?

You can’t drink caffeine before a nuclear stress test, but you can afterward if the doctor says it’s alright. Depending on the reason for your test and your results, you may need to avoid caffeine.

What should I avoid after a nuclear stress test?

After a nuclear stress test, you can generally return to your normal daily activities. You may want to shower, and it’s recommended that you drink plenty of fluids, wash your hands frequently, and avoid children and babies for 1 to 2 days.

Is it normal to feel bad after a nuclear stress test?

For most people, the effects of a nuclear stress test are mild and short-lasting. If your stress was caused chemically, the symptoms could be more pronounced.

Why am I so tired after a nuclear stress test?

A nuclear stress test involves stress on your cardiovascular system that is caused by exercise or chemicals. You may want to rest after this test, but you should feel back to normal after a night of rest.

During a nuclear stress test, you’ll have a radioactive tracer injected into your bloodstream.

The tracer will decay on its own over time and will pass harmlessly from your body through your urine and stool.

You can speed up this process by staying hydrated. You might also want to shower, wash your hands regularly, and avoid close contact with children and babies for a couple days after the test.