MRI Safety Guide: How to Prepare and Understand the Risks
Updated: 4 days ago
Is an MRI safe? For most people, yes. MRI uses a strong magnet and radio waves instead of radiation, and the scan itself is painless. The main risks come from metal and certain implants, which is why careful safety screening before every scan matters so much.
This guide explains the real MRI risks in plain language, how to prepare, and what you can do to make your scan safe and smooth.
How an MRI works, in brief
An MRI scanner is a large magnet shaped like a tube. When you lie inside it, the magnet lines up hydrogen atoms in your body. Short pulses of radio waves then make those atoms give off tiny signals. A computer turns the signals into detailed pictures.
Because MRI does not use X-rays, there is no ionizing radiation. You can read more about that in why MRI scans use no radiation. But MRI has its own safety rules, and most of them are about the magnet.
The main MRI safety risks
Metal objects
The MRI magnet is always on, even when no one is being scanned. It can pull metal objects toward it with great force. Keys, phones, hairpins, pens, oxygen tanks, and even some wheelchairs can become dangerous inside the scan room. That's why everyone who enters, including family members, is screened and asked to remove metal.
Implants and medical devices
Some implants are safe in an MRI. Some are safe only under certain settings. Others are not safe at all. Devices that always need to be checked include:
Pacemakers and implanted defibrillators
Cochlear implants
Insulin pumps and other drug pumps
Nerve or brain stimulators
Aneurysm clips
Metal fragments in the body, especially near the eyes
Some surgical clips, pins, plates, screws, or joint replacements
Many people with implants can still have an MRI safely. The team just needs to know the exact device first. If you have a device card, bring it. If not, your surgeon's office can often tell you the make and model.
Warmth during the scan
The radio waves can slightly warm the body. Most people feel little or nothing. Tell the technologist right away if any spot feels hot or uncomfortable. Metal in clothing, some medicine patches, and certain tattoos can sometimes cause a warm feeling, so mention these too. Learn more in are MRIs safe for patients with tattoos.
Loud noise
MRI scanners make loud knocking and buzzing sounds. You'll get earplugs or headphones to protect your hearing. Wear them for the whole scan.
Contrast dye
Some scans use a contrast dye, usually gadolinium, given through an IV. Most people have no problem. Some have mild side effects like a headache, nausea, or a brief cool feeling. Allergic reactions are uncommon. People with serious kidney disease need extra review before contrast. Always tell the staff about allergies, kidney problems, or past reactions to contrast.
Feeling anxious or closed in
The scanner can feel tight, and some people feel anxious. This is common and nothing to be embarrassed about. Tell your doctor and the staff ahead of time. Our tips on overcoming claustrophobia during an MRI can help.
Tell the team before your scan
The safety form is the most important step. Be complete and honest. Tell the staff if you:
Have any implant, device, or metal in your body
Have ever worked with metal, such as welding or grinding
Have had any surgery
Are pregnant or might be pregnant
Have kidney problems or allergies
Have had a reaction to contrast dye before
Wear a medicine patch, insulin pump, or glucose monitor
Feel anxious in tight spaces
If you're not sure about something, say so. It's much better to check than to guess.
How to prepare for your MRI
Follow your doctor's instructions. Most MRIs need no special prep. Some scans have rules about eating or drinking, so ask. See can I eat before an MRI.
Dress without metal. Wear comfortable clothes with no zippers, snaps, or metal buttons. You may be asked to change into a gown.
Leave valuables at home. Remove jewelry, watches, piercings, and hair accessories.
Bring your paperwork. Bring your doctor's order, ID, insurance card, and any implant cards.
Take your usual medicines unless your doctor tells you otherwise.
Arrive a little early to fill out the safety form without rushing.
During the scan
You'll lie on a padded table that slides into the scanner. The technologist will step into the next room but can see you, hear you, and talk with you the whole time. You'll usually have a call button to hold.
The most important thing you can do is stay still. Movement blurs the images and may mean a sequence has to be repeated. Here's what happens if you move during an MRI.
A few things that help:
Breathe slowly and steadily
Close your eyes if that feels better
Ask the technologist to tell you how long each part will take
Speak up if you feel pain, heat, or panic
After the scan
Most people go right back to their normal day. If you got contrast, you can usually eat and drink as normal. If you were given medicine to relax, follow the instructions you were given and have someone drive you home.
A radiologist reads your images and sends a report to your doctor. Your doctor will go over the results with you.
Frequently asked questions
Is an MRI dangerous?
For most people, no. The main risks are from metal and some implants, which is why screening is so important. When safety steps are followed, MRI is a very safe test.
Can I have an MRI if I have metal in my body?
Often, yes. It depends on the type of metal or device. Tell the staff about it before your scan so they can check whether it is safe.
Does an MRI hurt?
No. The scan is painless. Some people find lying still or the noise uncomfortable, but the scan itself doesn't hurt.
Is MRI contrast dye safe?
For most people, yes. Side effects are usually mild, and allergic reactions are uncommon. Tell the staff about allergies and kidney problems before your scan.
Can I have an MRI if I'm pregnant?
Tell your doctor and the MRI staff before your scan if you are pregnant or might be. They will decide together with you whether the scan should be done now. Read more in MRI safety during pregnancy.
Related reading
Schedule an MRI at Millenium MRI
Millenium MRI has centers in Ocala, Largo, and Tamarac, Florida, and in North Little Rock, Springdale, Jonesboro, and Marion, Arkansas. Our ARRT-certified technologists review your safety screening with you, and board-certified radiologists read every scan. Results are usually sent to your doctor within 24 hours, and same-day appointments are often available. We're open Monday through Friday, 9am to 5pm. Call your nearest center or request an appointment online.
This article is for general information and is not medical advice. Talk with your doctor about your specific situation.
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