Preparing for an MRI is mostly about removing anything metallic from your body and knowing what to expect once you’re inside the scanner. The process is straightforward, but the specifics depend on which body part is being scanned, whether contrast dye is involved, and whether you have any implants or medical devices. Here’s what to do before, during, and after.
What to Wear and What to Remove
Most MRI facilities will ask you to change into a hospital-provided gown and pants before the scan. You’ll need to remove all metallic personal belongings, including watches, jewelry, body piercings (if removable), hair clips, belt buckles, and even metallic drug delivery patches. Underwire bras are a common one people forget about. Some facilities also ask you to remove undergarments and replace them with site-supplied alternatives.
The simplest approach is to leave valuables at home and show up in comfortable, metal-free clothing. Elastic-waist sweatpants, a cotton t-shirt, and slip-on shoes make the check-in process faster. If you wear glasses, you’ll remove those before entering the scanner room too.
The Safety Screening Process
Before you get anywhere near the scanner, a technologist will walk you through a screening questionnaire. This isn’t a formality. MRI machines use extremely powerful magnets, and certain metal objects inside or on your body can move, heat up, or malfunction during the scan. The technologist will review your answers with you in person, then use a handheld metal detection wand to check for anything you might have missed.
Expect questions about surgical history, metallic implants, shrapnel or metal fragments, cardiac devices, cochlear implants, and any other hardware in your body. The FDA classifies implants into three categories: MR Safe (no restrictions), MR Conditional (safe only under specific conditions that must match the scanner being used), and MR Unsafe (cannot enter the scanner room at all). If you have an implant, bring the manufacturer’s name and model number so the team can verify its safety rating. Your surgeon’s office or the facility that placed the device can usually provide this information.
Patients with pacemakers or other active implants aren’t automatically disqualified. Many newer cardiac devices are MR Conditional, meaning the scan can proceed as long as the scanner settings fall within the device’s approved parameters. But this requires advance coordination, so let the scheduling team know about any implants when you book the appointment, not on the day of the scan.
Fasting and Dietary Restrictions
A standard MRI of the brain, knee, or spine typically requires no fasting at all. You can eat and drink normally beforehand. The rules change in a few specific situations.
If your scan involves intravenous contrast dye, you may be asked to avoid solid food for four to eight hours before the exam. The same fasting window applies if you’ll be receiving sedation. For certain abdominal scans, such as those evaluating blood flow to the intestines, the fasting window is about six hours, though water is usually still allowed. Cardiac MRIs that assess blood flow to the heart muscle have the strictest requirements: no food for two hours before the scan, and no coffee, tea, chocolate, or any other source of caffeine for a full 24 hours prior. Caffeine affects how the heart responds to the stress agents used during these exams.
Your scheduling confirmation should include specific instructions. If it doesn’t, call ahead and ask.
What to Know About Contrast Dye
Not every MRI uses contrast, but when it does, a small amount of a substance called gadolinium is injected into a vein in your arm. It helps certain tissues show up more clearly on the images.
Before receiving contrast, you may need a blood test to check kidney function. This is because the kidneys are responsible for flushing the dye out of your system. People with healthy kidneys clear it within 2 to 24 hours. For patients with severely reduced kidney function (a filtration rate below 30), gadolinium carries a risk of a rare but serious condition that affects the skin and connective tissue. If you have a history of kidney disease, mention it early so the team can check your bloodwork and decide whether contrast is appropriate.
After a contrast-enhanced MRI, drinking plenty of water helps your kidneys clear the dye faster. Most people resume normal activities immediately.
Managing Claustrophobia and Anxiety
The bore of a standard MRI scanner is a narrow tube, roughly 60 centimeters wide, and you’ll spend anywhere from 20 minutes to over an hour inside it depending on the exam. If enclosed spaces make you anxious, you have several options.
The first is simply knowing what to expect. The machine is loud, producing repetitive knocking and buzzing sounds. You’ll be given earplugs or headphones. The technologist will hand you a squeeze ball that triggers an alarm so you can signal for a break at any time, and you’ll be able to communicate through an intercom throughout the scan. Staying still is important for image quality, but the technologist can pause between sequences if you need a moment.
If you think you’ll need more help, ask your doctor about a mild oral sedative before the appointment. These are typically prescribed as a single dose to take shortly before the scan. Because sedation is involved, you’ll need someone to drive you home and you’ll likely be asked to fast for several hours beforehand, just as you would for contrast. For patients who need deeper sedation, some facilities offer IV sedation or, in rare cases, general anesthesia, though these require more advance planning and monitoring.
Wide-bore and open MRI machines exist and can be a good option for people with severe claustrophobia or larger body sizes. Not every facility has one, and image quality can vary, so ask about availability when scheduling.
Tattoos and Skin Considerations
Tattoos contain trace amounts of metal in the ink, and in rare cases this can cause the skin to heat up during the scan. The risk increases with larger tattoos and higher-strength magnets. Most people with tattoos undergo MRI without any problems, but you should mention any tattoos during screening. If you feel warmth, tingling, or discomfort at a tattoo site during the scan, squeeze the alert ball immediately so the technologist can pause the exam.
Pregnancy and MRI
MRI does not use radiation, which makes it fundamentally different from CT scans and X-rays. Research has not shown harmful effects on the developing fetus at the magnetic field strengths used in clinical scanners (1.5T and 3T). A pregnant patient can undergo MRI at any stage of pregnancy when the clinical benefit justifies the scan, as outlined by the American College of Radiology.
Contrast dye is a different matter. Gadolinium is not routinely given during pregnancy. When it’s considered, the decision is made on a case-by-case basis with a careful risk-benefit analysis, because the effects of gadolinium on fetal development are not fully understood.
What to Expect During the Scan
You’ll lie on a motorized table that slides into the scanner. The technologist will position a special coil (a device that helps capture the images) around or near the body part being scanned. Padding will be placed around you, both for comfort and to prevent skin-to-skin contact that could cause warming. You’ll get earplugs, the squeeze ball, and a quick reminder to hold still.
Once the scan starts, you’ll hear a series of loud, rhythmic sounds that change in pattern as different image sequences run. Each sequence lasts a few minutes. Between sequences there are brief pauses. For some abdominal or chest scans, you’ll be asked to hold your breath for 10 to 20 seconds at a time. The technologist will coach you through this over the intercom.
The scan itself is painless. The most common complaints are boredom and the noise. Some people fall asleep.
After the Scan
If you didn’t receive sedation or contrast, there’s no recovery period. You can drive, eat, and go back to work immediately. If you had contrast, drink extra water for the rest of the day. If you were sedated, plan to rest and have someone available to drive you home.
Results are typically read by a radiologist and sent to your ordering physician within a few business days, though urgent findings may be communicated sooner. Some facilities offer patient portal access where you can view the report and images directly.