How to Prepare for a PET Scan


A Positron Emission Tomography scan, also known as a PET scan, is a common test to check for a wide range of health issues. Before the test, you will be injected with a small amount of radioactive glucose. The PET machine will track this contrast material to create detailed images of your organs and tissues.[1] Provide your doctor with important information about your health before the test, follow your doctor’s instructions for how to prepare, and find ways to increase your comfort during the test.

Part 1
Talking with Your Doctor before the Test

Talking with Your Doctor before the Test on How to Prepare for a PET Scan

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If you have had a reaction to contrast material in the past, it could happen again. A reaction may include itchy eyes, hives, sneezing, nasal congestion, restlessness, rashes, nausea, vomiting, pain, tremors, or dizziness.[2] Be sure to let your doctor know if you have ever had a reaction and what happened.[3] If the reaction was severe, then your doctor will likely choose a different test option. Tip: Be sure to tell your doctoreven if you only had a mildreaction. If they decide to goahead with the test, they willneed to watch you for symptoms ofa reaction during and after thetest.Tip: Be sure to tell your doctor evenif you only had a mild reaction. Ifthey decide to go ahead with the test,they will need to watch you forsymptoms of a reaction during andafter the test.Tip: Be sure to tell your doctor even if youonly had a mild reaction. If they decide togo ahead with the test, they will need towatch you for symptoms of a reaction duringand after the test.Tip: Be sure to tell your doctor even if you only had a mild reaction.If they decide to go ahead with the test, they will need to watch youfor symptoms of a reaction during and after the test.Tip: Be sure to tell your doctor even if you only had a mild reaction. If theydecide to go ahead with the test, they will need to watch you for symptoms ofa reaction during and after the test.

Talking with Your Doctor before the Test on How to Prepare for a PET Scan

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You will be exposed to a small amount of radiation during the test, which could be dangerous for a fetus. If you are breastfeeding, the radioactive material may get into your breastmilk, and you might need to pump and dump your breastmilk for 24 hours after the test until it is out of your system.[4] This does not automatically mean you cannot have a PET scan. However, you and your doctor will need to weigh the potential benefits of the test against the risks.[5]

Talking with Your Doctor before the Test on How to Prepare for a PET Scan

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It is important to let your doctor know if you have been sick lately or experienced any other significant health problems. If the problems were severe, then your doctor might consider delaying the test or looking for an alternative.[6] For example, if you recently had pneumonia, your doctor might consider delaying the test.

Talking with Your Doctor before the Test on How to Prepare for a PET Scan

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Tell your doctor about all of the over-the-counter and prescription medications, supplements, and herbs you take on a regular basis. Depending on what you take and what the test is for, your doctor may ask you to abstain from taking 1 or more of these medicines in the days leading up to the test.[7] You may receive special instructions to prepare for the test if you have diabetes and take medication to control it.[8]

Part 2
Following Your Doctor’s Guidelines

Following Your Doctor’s Guidelines on How to Prepare for a PET Scan

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Your doctor may give you an instruction sheet with specific guidelines to prepare yourself for the test. Read through the guidelines carefully and follow your doctor’s instructions exactly. Call your doctor prior to the test if you have any questions or concerns.[9] If you did not receive an instruction sheet, you may call your doctor’s office to ask if there are any special guidelines you should follow.

Following Your Doctor’s Guidelines on How to Prepare for a PET Scan

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Check with your doctor if you are unsure about whether or not to continue medication. If you take medications for diabetes, make sure to take a dose no less than 4 hours before your test.[10] For example, if your test is scheduled for 10:00 am, then take your dose by 6:00 am.

Following Your Doctor’s Guidelines on How to Prepare for a PET Scan

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Patients are usually directed to follow a water-only fast for 6 hours prior to the PET scan. During this time, do not eat any food or consume beverages that contain calories, such as juice, milk, or sports drinks. Only drink water during this time frame. However, if you have been instructed to fast for a shorter or longer period prior to the test, then you can follow this guideline instead.[11] In addition to fasting, your doctor may advise you to follow a specific diet for the 24 hours leading up to the test, such as a low-carbohydrate diet for a Myocardial Viability PET scan.[12] Gum and mints are not permitted while you are fasting either, so avoid these in the 6 hours before your test.

Following Your Doctor’s Guidelines on How to Prepare for a PET Scan

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If you have a heart condition or the test is checking for heart problems, then you will need to abstain from caffeine for the 24 hours leading up to the test. Caffeinated beverages include coffee, tea, cola, and energy drinks. However, chocolate also contains a small amount of caffeine.[13] Ask your doctor if you are unsure if this applies to your situation. Tip: Make sure to drink plenty ofwater leading up to the test tokeep yourself hydrated! It isalso recommended to drink40  fl oz (1,200 mL) of waterfollowing the test to help yourbody excrete the contrastmaterial.[14]Tip: Make sure to drink plenty ofwater leading up to the test to keepyourself hydrated! It is alsorecommended to drink 40  fl oz(1,200 mL) of water following thetest to help your body excrete thecontrast material.[14]Tip: Make sure to drink plenty of waterleading up to the test to keep yourselfhydrated! It is also recommended to drink40  fl oz (1,200 mL) of water followingthe test to help your body excrete thecontrast material.[14]Tip: Make sure to drink plenty of water leading up to the test to keepyourself hydrated! It is also recommended to drink 40  fl oz(1,200 mL) of water following the test to help your body excrete thecontrast material.[14]Tip: Make sure to drink plenty of water leading up to the test to keepyourself hydrated! It is also recommended to drink 40  fl oz (1,200 mL) ofwater following the test to help your body excrete the contrast material.[14]

Following Your Doctor’s Guidelines on How to Prepare for a PET Scan

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These activities can affect the results of your test, especially if the test is for your heart. Skip your workout if you normally do strenuous activities and cancel any massage appointments you may have made for the day or 2 before your test.[15] Strenuous activities include things like running or lifting heavy weights, but other activities may also be considered strenuous depending on your health. Talk with your doctor if you are unsure if an activity counts as strenuous.

Part 3
Increasing Your Comfort for the Test

Increasing Your Comfort for the Test on How to Prepare for a PET Scan

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The PET scan will last about 30 to 60 minutes, and during this time you will be in a large, open-ended tube. If you are claustrophobic (have trouble with small spaces), then let your doctor know. They might be able to provide you with a sedative prior to the test to help you relax.[16] Keep in mind that you may only be partially enclosed in the tube depending on the part of your body that the machine is scanning. For example, if the machine is focused on your abdomen, then your head and upper body may be outside of the tube.

Increasing Your Comfort for the Test on How to Prepare for a PET Scan

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You will need to change into a hospital gown prior to the test. Wear something loose and comfortable that you can easily take off before the test and put back on after the test is over.[17]Tip: Avoid bringing jewelry orvaluables into the hospital withyou. If you have to leave themunattended, they might get stolenor lost.[18]Tip: Avoid bringing jewelry orvaluables into the hospital with you.If you have to leave them unattended,they might get stolen or lost.[18]Tip: Avoid bringing jewelry or valuablesinto the hospital with you. If you have toleave them unattended, they might get stolenor lost.[18]Tip: Avoid bringing jewelry or valuables into the hospital with you. Ifyou have to leave them unattended, they might get stolen or lost.[18]Tip: Avoid bringing jewelry or valuables into the hospital with you. If youhave to leave them unattended, they might get stolen or lost.[18]

Increasing Your Comfort for the Test on How to Prepare for a PET Scan

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This will help you to feel calmer before going into the test. Take a deep breath in through your nose to the count of 4, and then release it through your mouth as you count to 8. Repeat this as many times as you like before the test to help calm yourself. You will be instructed to hold your breath at certain times during the test, but you can continue deep breathing in between those times.[19]