Patients often want to know if they’ll need to fast in preparation for an MRI scan. No one likes to go hungry, after all. The good news is that most MRI procedures don’t require dietary restrictions. Almost everyone can eat and drink as usual on the morning of their scan. The same is true following the MRI; if you’re craving a post-imaging cheeseburger, you can usually go for it.
There are a few exceptions, though. If you have an MRI with a contrast agent, your doctor may ask that you fast for a few hours prior to the scan. While nausea is a rare side effect of the contrast dye, physicians like to err on the side of caution.
Your doctor may instruct you to skip food and beverages for up to 4 hours prior to an MRI of the abdomen or pelvis, as well. It all depends on the particular type of scan. The main takeaway here, though, is that more often than not, patients can eat and drink however they’d like to prior to an MRI scan.
But MRIs are only one of the imaging modalities radiologists use to help diagnose their patients. Ultimately, your physician will tell you if you need to restrict your diet prior to a given procedure. That said, here’s what you can typically expect before heading to your diagnostic imaging appointment:
X-Ray Procedures and Diet
Most X-ray procedures don’t require you to fast, but a few do. If your doctor orders a barium swallow X-ray, they’ll probably ask you not to eat or drink for six hours prior to the appointment. Some X-rays of the abdomen also perform better with fasting. As always, your physician should let you know how to prepare for your test, and if you have any questions about dietary restrictions, they’ll be happy to answer them.
The same is true of CT scans, which use X-ray images and special digital tools to construct a 3D image of the body’s interior. If you need a CT scan with a contrast agent, your doctor might ask you not to eat or drink anything but clear liquids in the time leading up to the test.
Ultrasound Imaging and Diet
Ultrasounds create images using sound waves, and like other types of diagnostic imaging, they sometimes do require fasting. Abdominal ultrasounds, in particular, require a few hours without food as part of a study of the gallbladder or the rest of the biliary tract.
However, ultrasounds studying other parts of the body do not require you to skip food and drink, for the most part.
Fasting for PET Scans
PET scans rely on the introduction of radiotracers into the body, usually through injection, swallowing, or inhalation of a gas. Generally, radiologists do ask patients not to eat for a few hours prior to a PET scan. They may also tell you not to drink sugary beverages.
Your physician may tell you to eat a low-carb diet for some time before your scan, followed by several hours of total fasting, with the exception of water.
However, as in all cases of diagnostic imaging, ask your physician if you can eat or drink before having a procedure. They’ll be happy to help you prepare.