An MRI (magnetic resonance imaging) scan is a medical imaging technique that uses strong magnetic fields and radio waves to create detailed images of the inside of the body. MRI scans are often used to examine organs, soft tissues, bone marrow, and other internal body structures.
During an MRI scan, it is very important not to eat or drink anything for several hours beforehand. This is because eating or drinking too close to the scan can significantly impact the quality of the images obtained. There are a few key reasons why consuming food and beverages needs to be avoided before an MRI.
Risk of Aspiration
One of the most serious risks associated with eating or drinking before an MRI is aspiration. Aspiration occurs when food, saliva, liquids, or stomach contents are inhaled into the airways leading to the lungs. This can cause choking, breathing problems, and pneumonia.
When lying flat inside the MRI scanner, it is easier for items to travel up from the stomach and be accidentally inhaled into the lungs. The magnetic fields used during the scan can also affect the way food and liquids move within the body, increasing this risk. Avoiding food and drink for the recommended time (often 3-4 hours) minimizes the amount of material in the stomach that could potentially be aspirated.
Impact on Image Quality
Consuming food and beverages before an MRI can negatively impact the quality of the scan images. MRI creates images using the magnetic properties of water and fat. Food and liquids in the stomach and intestines alter the magnetic properties in that area of the body.
This can make the tissues and organs harder to visualize on the scan. It also leads to distortions and artifacts on the images that can obscure findings or mimic real medical issues. Radiologists may have difficulty interpreting the scan accurately. Therefore, fasting helps avoid these factors that degrade the diagnostic sensitivity of the MRI.
Discomfort and Safety Issues
Having a full stomach during an MRI increases the chance of experiencing discomfort or other safety issues. Lying still for 30 to 90 minutes can be uncomfortable after eating a full meal. Digestion processes may cause bloating, gas, or cramps which are amplified when confined inside the scanner tunnel.
The magnetic fields used during MRI can also cause nausea, vertigo, and a metallic taste in the mouth. These effects are made worse if food and liquids are moving through the digestive system during the scan. Fasting helps reduce this discomfort and the urge to suddenly move or vomit while inside the scanner.
Required Fasting Times for MRI
The fasting requirements depend on the type of MRI being performed and can vary between facilities. Some general guidelines include:
MRI without Contrast
For a standard MRI without intravenous contrast dye, fasting for 2 to 3 hours is typically recommended. Clear liquids may be permitted up to 1 hour before the scan.
MRI with Contrast
For MRI studies using contrast dye, a longer fasting period of 3 to 4 hours is usually required. All food and liquids should be avoided during this time.
Breast MRI
Some breast MRI protocols request fasting for 4 to 6 hours to reduce artifacts from stomach contents. However, other facilities allow light meals up to 4 hours prior.
MRI with Sedation
For patients who require sedation during their MRI, fasting times of 6 to 8 hours are common. This stricter fasting helps prevent aspiration since the sedative medication increases this risk.
Bowel MRI
For MRI studies of the abdomen and pelvis, bowel prep with a liquid diet and laxatives may be necessary the day before. This empties the bowels and improves visualization.
Always follow the exact fasting instructions provided by the MRI facility and technologist. They will give guidelines tailored for your specific scan and medical factors.
What You Can and Cannot Consume Before an MRI
Since MRI requires fasting from all food and most liquids, this greatly limits what can be consumed in the hours leading up to the scan. Here are some specifics:
Allowed
– Water – Plain water is usually permitted up until 1 hour before the MRI scan. Stay well hydrated.
– Clear juices – Clear fruit juices without pulp, such as apple juice or white grape juice, may be allowed.
– Tea/coffee – Plain tea or black coffee without milk or creamer may be approved.
– Clear broth – Fat-free clear broths without particles may be permitted.
– Plain gelatin – Clear gelatin without added fruit or toppings is sometimes allowed.
Not Allowed
– Solid foods – No solid foods, meals, or snacks can be consumed during the required fasting period.
– Milk – Milk, cream, soy milk, and other milk products are prohibited.
– Smoothies – Fruit smoothies and shakes with pulp should be avoided.
– Soda – Soda, carbonated drinks, and sparkling water are not permitted.
– Alcohol – Alcoholic beverages should be avoided for at least 12-24 hours prior to an MRI scan.
– Citrus – Citrus juices and drinks with acidity can cause digestive upset during the scan.
– Coffee – Coffee with milk, cream, or sugar is not allowed.
Always check with your MRI technologist if you are unsure about consuming a particular food, drink, or supplement beforehand.
Reasons Why You Still Must Fast Before an MRI
Patients will sometimes question why fasting is necessary for modern MRI scanners if the images are so detailed. Here are some reasons why fasting protocols remain important:
Patient Safety
Fasting prevents aspiration, discomfort, and other safety issues that can arise from lying still with a full stomach during the scan. Patient health and wellbeing is the top priority.
Diagnostic Accuracy
Even small amounts of food or liquid in the gastrointestinal tract can distort images and potentially hide or mimic disease. Radiologists rely on the best quality scans.
Scanner Strength
Although MRI magnets have gotten stronger, the effects of food and liquids on image quality persist. Fasting provides ideal conditions.
Consistency
Standard pre-MRI fasting makes sure all patients are optimally prepared. Varying protocols between patients would be chaotic.
Compare Scans
Fasting protocols allow for consistent preparation when comparing a patient’s current and past MRI scans for changes.
While modern MRIs are highly advanced, fasting remains fundamental to ensure safety, comfort, and diagnostic accuracy during the scan. Follow your facility’s guidelines.
What Happens if You Do Eat or Drink Before an MRI?
Despite fasting instructions, patients may sometimes inadvertently eat or drink too close to their scheduled MRI. So what happens in these cases?
Here are the common scenarios:
Scan Rescheduled
If you notify the technologist that you ate or drank within the prohibited timeframe, the scan will most likely be rescheduled to a later date when you can properly fast.
Delay the Scan
The MRI facility may have you wait an extra period of time to allow more digestion and clearance of the stomach. Then the scan proceeds.
Proceed With Caution
If fasting was borderline, the technologist may decide to proceed with the MRI but take extra care regarding your positioning and comfort.
Receive IV Fluids
You may be given IV fluids before the scan to help dilute and flush the stomach contents.
Rinse the Mouth
For only minor eating and drinking, you may be instructed to rinse your mouth out with water before proceeding.
Ideally though, MRI facilities want patients to strictly adhere to fasting instructions without exceptions. Always inform them in advance if you have eaten or drank any amount before coming in for your scan. Be prepared that your appointment may need to be delayed or rescheduled.
Tips for Successfully Fasting Before an MRI
Here are some useful tips to help you successfully complete the required fasting before your MRI scan:
Schedule Accordingly
Book early morning MRI appointments to make fasting easier overnight. Or schedule late afternoon to fast during the day.
No Snacking
Avoid snacking after meals once the fasting period has begun. Grazing will make you hungrier.
Stay Hydrated
Drink extra water leading up to the fasting period to keep hydrated.
Limit Caffeine
Minimize caffeine which can trigger hunger. Herbal tea can help calm appetite.
Rest Well
Get adequate sleep the night before an MRI to feel rested and less hungry when fasting.
Distract Yourself
Keep busy and engaged in activities to distract your mind from food.
Avoid Cooking
Don’t prepare meals for others while you are fasting, as the temptation and smells can be challenging.
Chew Gum
Sugar-free gum can help satisfy the urge to chew and eat.
Manage Medications
Take only necessary medications during fasting with sips of water.
With preparation and discipline, you can follow pre-MRI fasting successfully. The scan results are worth the temporary hunger!
Who Should Not Fast Before an MRI?
While most patients should adhere to fasting, there are some situations where fasting may not be required or recommended before an MRI:
| Group | Guidance |
|---|---|
| Pregnant women | After first trimester, light snacks may be permitted if needed |
| Diabetics | May require small carb-controlled snacks and glucose monitoring |
| Kidney disease | Must closely monitor hydration and may drink up to scan time |
| Elderly | May struggle with fluid/electrolyte balance if fasting too long |
| Young children | Cannot remain NPO for extended periods, so shorter fasting times |
Additionally, patients who need urgent MRIs for medical emergencies may undergo scanning without optimized fasting times.
Discuss any conditions or circumstances with your doctor that may require tailored fasting instructions for your situation. There is some flexibility when medically warranted.
Can You Drink Contrast Before an MRI?
Oral contrast (liquid dye solutions) may be given to patients prior to an MRI of the abdomen or pelvis. This is different than IV contrast dye used during some scans.
Purposes of oral contrast for MRI include:
- Distend areas such as the stomach, small bowel, colon to better see anatomy
- Enhance visibility of intestinal walls, bowel obstructions, and lesions
- Highlight abnormalities and diseases in the digestive tract
Oral contrast agents contain substances such as barium or iodine to alter signal intensity on the images. Types include:
- Barium sulfate – thick chalky liquid that cannot be absorbed, for stomach/bowel MRIs
- Gadobenate dimeglumine – iodine agent, often given in watery dilution for bowel scans
- Iron oxides – alter magnetic properties of nearby tissues, increasing contrast
The correct dose and timing for consuming oral contrast is important and will be instructed by the radiologist and technologist. Though it involves drinking a liquid, this is different than regular food and beverages that need to be avoided. Oral contrast is administered strategically as part of the scanning procedure.
Can You Chew Gum or Suck Candy Before an MRI?
Technically any eating or oral intake should be avoided during the pre-MRI fasting period. However, occasionally small allowances may be made:
– Chewing small amounts of flavorless gum may be permitted, as it is not swallowed.
– Sucking on hard candies like mints may sometimes be allowed, but ideally not immediately before lying down in the scanner.
– Small sips of plain water may be approved for taking essential medications.
These exceptions are not guaranteed and only apply to traces of substances, not full meals/beverages. Patients should clarify with the MRI staff beforehand whether any oral intake like gum or candy will be allowed leading up to their scan. Don’t assume it will be permitted unless given explicit approval. Complete fasting is ideal.
Can You Brush Your Teeth Before an MRI?
Yes, basic oral hygiene is still recommended on the day of your MRI scan. Unless indicated otherwise, you may brush your teeth as you normally would before coming in for the MRI.
Just be sure to spit out any toothpaste or rinse water, rather than swallowing it. Toothbrushing without water is also fine. The goal is to clean your mouth while not introducing anything into your digestive system.
Brushing your teeth before the scan helps reduce the risk of aspiration by:
- Removing food debris from chewing
- Keeping bacteria levels in the mouth low
- Freshening breath if you cannot eat/drink
- Clearing away sugars that could impact imaging
Basic brushing with a small amount of water should not significantly impact MRI results, compared to the benefits for hygiene and safety. Just be sure to consult the facility if toothpaste ingredients would be an issue, such as iron oxide compounds.
Can You Take Medications Before an MRI?
Patients are often instructed to take medications as prescribed before an MRI, even during fasting. This includes prescription drugs, over-the-counter medications, supplements, etc.
However, there are some medication precautions for MRI:
- Oral diabetic medications may need adjusted dosing with fasting.
- Diuretics, stimulants, narcotics could cause discomfort lying still.
- Drugs with iron could distort abdominal images.
- Metformin may need held 48 hours before MRI with contrast.
Also, oral medications on the day of the scan should only be taken with small sips of water, not a large glass.
Importantly, certain medical patches for conditions like motion sickness should be removed prior to MRI, as they contain metals. Always inform the technologist of any medications, supplements, and patches taken. Some adjustments may be required. But most routine medications can be safely continued leading up to the scan after confirming with your doctor.
Should You Tell Your MRI Technologist If You Accidentally Ate?
Yes, you should always inform the MRI technologist if you accidentally consumed any food or liquids within the prohibited timeframe before your scan. Even if it was a small amount, they need to know.
Being transparent allows the staff to take any necessary precautions, such as:
- Rescheduling your appointment until you can properly fast.
- Having you wait an additional period of time before scanning.
- Giving you IV fluids to help clear your stomach.
- Adjusting your positioning to reduce aspiration risk.
- Taking special care during image review, if proceeding cautiously.
While you may feel embarrassed about not following preparation instructions, it is in your best interest to be forthcoming. The technologists need accurate information to perform the scan safely and optimize the diagnostic quality of your test results.
Conclusion
Pre-MRI fasting is an indispensable part of preparation for the scan. Avoiding food and liquids prevents complications with patient safety, comfort, and imaging quality. While fasting can be inconvenient, it maximizes the accuracy of MRI results.
If you accidentally eat or drink before your scheduled scan, always notify the MRI staff. They can then determine the best course of action, which may include rescheduling your appointment. With adequate preparation, fasting for an MRI is manageable and an important component of your overall experience.
