What Not to Do Before an MRI Scan

Preparing for an MRI scan is mostly straightforward, but there are several things you should specifically avoid doing before your appointment. Getting these wrong can delay your scan, reduce image quality, or create a genuine safety risk. Here's what not to do before an MRI — and why.

Don't Wear Metal

This is the single most important rule. The MRI scanner produces an extremely powerful magnetic field (30,000-60,000 times stronger than the Earth's), and any ferromagnetic metal in the scanning room can become a dangerous projectile or distort your images. Before your scan, don't wear or bring:

• Jewellery — rings, necklaces, bracelets, earrings, body piercings
• Watches, fitness trackers, smartwatches
• Hair clips, grips, bobby pins
• Belts with metal buckles
• Clothing with metal zips, buttons, rivets, or underwire (jeans are the classic problem)
• Glasses with metal frames (check with the centre — titanium frames are often fine)
• Coins, keys, pens, pocket knives

Leave these at home or in the secure locker at the centre. If you forget something, the radiographer will catch it during the safety check — but it saves time if you come prepared. See our full preparation guide.

Don't Forget to Declare Implants and Devices

If you have any metal implants, surgical hardware, or medical devices, you must declare them on the safety questionnaire. Items to disclose include:

• Pacemakers and defibrillators (ICDs)
• Cochlear implants
• Surgical plates, screws, pins, rods, or wires
• Joint replacements (hip, knee, shoulder)
• Metallic heart valves
• Intracranial aneurysm clips
• Spinal cord stimulators, neurostimulators, deep brain stimulators
• Insulin pumps
• IUDs with metal components (Mirena, copper coil)
• Metallic foreign bodies (shrapnel, metal fragments in the eyes from grinding or welding)

Many modern implants are MRI-compatible (MR Conditional), but this must be verified before scanning. Bring your implant card or documentation.

Don't Wear Certain Cosmetics

Some cosmetics contain metallic particles that can interfere with the scan or cause skin irritation:

• Eye makeup — Mascara, eyeliner, and some eyeshadows contain iron oxide. The particles can cause localised heating and image artefact, particularly for brain and facial MRI. Best to come without eye makeup.
• Metallic nail polish — Glitter and metallic polishes may contain metal particles.
• Hair products — Certain sprays and gels contain metallic compounds. Wash your hair normally but skip the styling products.
• Fake tan — Some contain metallic pigments.
• Antiperspirant — Contains aluminium. Generally safe, but if you're having a shoulder or chest MRI, you may be asked to skip it on the day.

The simplest approach: attend with clean skin and no products, if possible.

Don't Eat When Fasting Is Required

Most MRI scans don't need fasting. But certain abdominal and pelvic scans do:

• Liver MRI — Fast for 4-6 hours. Food stimulates bile flow and gallbladder contraction, which can obscure the images.
• MRCP (bile duct imaging) — Fast for at least 4 hours. No food, no chewing gum, no smoking. Anything that triggers bile secretion reduces image quality.
• Abdominal MRI — Often 4-6 hours fasting, though some protocols allow light food.
• Small bowel MRI — Fasting required, plus you'll drink a contrast preparation beforehand.

Check your booking confirmation for specific instructions. Water is usually permitted during the fasting period (and staying hydrated is encouraged, especially if you're having contrast).

Don't Skip Your Medications (Unless Told To)

Continue your regular medications as normal unless your scanning centre or doctor has given specific instructions to stop. This includes blood pressure medication, statins, and most daily prescriptions. If you're diabetic and need to fast, speak to your doctor about adjusting insulin timing.

Don't Bring Electronics into the Scanning Room

Mobile phones, smartwatches, tablets, laptops, car key fobs — all must stay outside the scanning room. The magnetic field will permanently damage these devices. Bank cards with magnetic strips will be wiped. Even contactless cards can be damaged. Use the secure locker provided.

Don't Arrive Late

MRI appointments run on a tight schedule, and centres often book back-to-back. If you arrive late, there may not be enough time for the safety screening and your appointment may need to be rescheduled (potentially at your cost). Aim for 15-20 minutes early.

Don't Drink Caffeine Before a Cardiac MRI

If you're having a cardiac MRI (especially a stress cardiac MRI), avoid all caffeine for 24 hours beforehand. This means no coffee, tea, energy drinks, cola, or chocolate. Caffeine affects heart rate and coronary blood flow, which can compromise the diagnostic accuracy of the scan.

Don't Forget to Use the Toilet

MRI scans last 20-60 minutes, and you need to lie completely still throughout. A full bladder becomes very uncomfortable very quickly. Use the toilet just before the scan starts. Exception: some pelvic scans require a moderately full bladder — you'll be given specific instructions if this applies.

Don't Panic About the Noise

MRI scanners produce loud knocking, buzzing, and clicking sounds at 80-100+ decibels. This is completely normal — it's the gradient coils vibrating as they switch on and off. You'll be given ear protection (plugs or headphones). Being prepared for the noise reduces anxiety significantly. Read our guide on what to expect during an MRI.

Frequently Asked Questions

Can I wear a sports bra for an MRI?

Yes, if it has no underwire, no metal clasps, and no metal hooks. A simple pull-on cotton sports bra is fine. If yours has any metal, you'll be asked to remove it. Most centres provide a gown.

Can I drink water before an MRI?

Yes, for almost all scan types. Staying hydrated is actually recommended, especially if you're having contrast. Only specific abdominal scans may restrict fluids — your booking confirmation will state this.

Can I wear contact lenses during an MRI?

Standard soft contact lenses are completely safe. Hard or gas-permeable lenses are generally fine too, but mention them to the radiographer as some very old designs may contain trace metals.

What happens if I accidentally eat when I should have fasted?

Tell the radiographer. Depending on what you ate, how much, and when, they may still be able to proceed. Or they may need to reschedule. Food in the stomach and active bile flow can obscure the structures the scan needs to show, particularly for liver, pancreas, and bile duct imaging.