Magnetic resonance imaging (MRI) is a medical imaging technique that uses strong magnetic fields and radio waves to generate detailed images of the inside of the body. It is a common diagnostic tool used to examine tissues, organs, and other internal body structures.
To get quality results from an MRI scan, patients are often asked to follow specific preparation guidelines before the procedure. One common instruction is to avoid eating for several hours beforehand. So is an empty stomach really necessary for an MRI exam? Let’s take a closer look at the facts.
Why fasting may be recommended before an MRI
Here are some of the main reasons why a doctor or technician may recommend fasting (avoiding food and drink) before an MRI:
- To prevent nausea – The MRI machine produces loud banging noises that can cause nausea or vomiting for some patients. Having an empty stomach minimizes this risk.
- To avoid artifacts – Food and drink in the digestive tract can affect image quality. Liquids and solids inside the body show up differently than soft tissues on MRI results and may create unwanted artifacts that obscure the area being examined or lead to a misdiagnosis.
- For abdominal/pelvic exams – Images of the abdominal and pelvic regions will show greater detail if the nearby digestive organs are empty and not filled with food or fluids.
- For anesthesia – If the patient will receive general anesthesia or sedation for the MRI, they will need to have fasting precautions to prevent aspiration of stomach contents into the lungs while unconscious.
Thus, fasting helps provide clearer images and reduces safety risks in many MRI scenarios. However, the requirements depend a lot on the part of the body being scanned.
How long should fasting last before an MRI?
There are no universally standard fasting guidelines for MRI exams. Requirements can vary between facilities and diagnostic centers. Here are some typical fasting recommendations:
- 2-4 hours – For most non-abdominal MRIs like those of the head, neck, spine, joints, breasts, etc.
- 6-8 hours – For abdominal MRIs to allow time for the stomach to fully empty.
- 8+ hours – For abdominal and pelvic scans of patients with slower gastric emptying.
Of course, these are just general timelines. Patients may be instructed to fast for shorter or longer pre-MRI starvation periods depending on factors like:
- Which body part is being imaged
- Whether contrast dye will be administered
- Their recent food intake and health status
- Standard protocols at a specific imaging center
The best advice is to carefully follow whatever fasting directions are provided by the MRI facility and technician.
Are there exceptions when fasting is not necessary?
While an empty stomach is ideal, there are some situations where fasting may not be required or recommended for an MRI. For example:
- Infants – Babies undergoing MRI scans rarely need to fast since their digestive systems empty so quickly.
- Children – Young children may be allowed sips of clear liquids before a non-abdominal MRI to avoid dehydration.
- Diabetics – Patients with diabetes mellitus should not fast in a way that causes severe hypoglycemia.
- Emergencies – In urgent situations like trauma, stroke, etc., MRI may be performed immediately without fasting.
- Mammograms – Breast MRIs usually do not require fasting preparations.
Additionally, facilities may make exceptions for patients who cannot safely tolerate fluid/food restriction for extended periods. But in such cases, the diagnostic quality of the results may be suboptimal.
What can be consumed before an MRI scan?
When fasting is necessary before MRI, patients are restricted to only certain types of fluids and foods up until 2-4 hours before scan time. Recommended items include:
- Water
- Black coffee or plain tea (no milk or cream)
- Clear broths and soups (without solid pieces)
- Clear fruit juices without pulp (apple, white grape, lemonade)
- Sports drinks like Gatorade
- Hard candies
- Gelatin foods
Avoid any milk products as well as pulpy juices with fruit fiber like orange juice. Also, refrain from alcohol which can interact with anesthesia if it will be administered.
What should be avoided before an MRI scan?
Here are some dietary restrictions to follow leading up to an MRI procedure requiring pre-scan fasting:
- Solid foods – No meat, grains, vegetables, etc. Liquids only.
- Milk, yogurt, ice cream – Dairy products can affect image quality.
- Alcohol, caffeine – Interfere with medication, cause dehydration.
- High-fiber foods – Can leave solid particles behind in GI tract.
- Fatty foods – Longer gastric emptying time so require longer fasting.
Also avoid iron supplements or contrast agents for 24-48 hours pre-MRI since they can distort the abdominal images. Check with your doctor about any medications that may need adjustment like metformin, insulin, etc.
What happens if you eat before an MRI requiring fasting?
While fasting may be inconvenient, it is generally recommended for good reason. But what if you accidentally eat before an MRI? Here’s what you can expect:
- Safety risks like nausea and vomiting while inside the MRI machine.
- Impaired image quality due to food/fluid artifacts.
- Potential need to reschedule and repeat the MRI procedure later.
- Possibility of needing additional MRI sequences or longer scan times.
- Oral contrast solution to improve visibility around digestive structures.
In some cases, the radiologist may determine that the study can still be completed and useful information obtained by having the patient drink some water just before the scan. Still, fasting is advised to get the clearest results on the first try.
How to prepare the day before an MRI
Proper preparation the day before an MRI scan requiring fasting can help ensure it goes smoothly. Here are some tips:
- Drink plenty of fluids to stay hydrated.
- Have a light dinner of foods that digest easily.
- Avoid alcohol, caffeine, and iron supplements.
- Stop eating and switch to clear fluids in the evening.
- Set cell phone alarms to remind yourself not to eat after midnight.
- Arrange for transportation to the MRI facility as you won’t be able to drive until after the scan.
- Pack a small cooler bag with approved clear beverage options to sip on until 2-3 hours before the MRI appointment.
Preparing properly the night before by starting your fast early makes it easier to stick with the instructions for the full duration.
Tips for easing fasting discomfort before an MRI
Going without food or liquids can cause symptoms like hunger, thirst, dizziness, and headaches. Here are some tips to help:
- Rest and relax as much as possible after starting to fast.
- Distract yourself with music, movies, light reading, etc.
- Apply a cool compress to the forehead or back of neck if headaches strike.
- Try sucking on hard mints, chewing gum, or eating ice chips for dry mouth.
- Use straws to sip approved clear fluids slowly up till the cutoff time.
- Keep the MRI facility’s number handy to call if fasting becomes unbearable.
Staying calm and utilizing distractions and other comfort measures can help you successfully complete the necessary pre-MRI fasting period.
Risks related to prolonged fasting for MRI
While most patients can tolerate short-term fasting without problems, there are some risks to be aware of with prolonged food restriction before an MRI:
- Hypoglycemia – Dangerously low blood sugar, especially for diabetics.
- Dehydration and electrolyte abnormalities.
- Headaches, fatigue, irritability, and dizziness.
- Fainting or syncope.
- Nausea and vomiting if fasting period is extended.
- Hunger and thirst leading to inability to complete the MRI exam.
Patients who are pregnant, have chronic medical conditions, or take certain prescription medications may be more susceptible to these risks from fasting. Close monitoring and medical supervision may be required in some cases, along with adjustments to the fasting protocols.
Can medicines be taken while fasting for MRI?
In general, most prescribed drugs and over-the-counter supplements should be continued as normal even while fasting in preparation for an MRI. However, there are a few medication-related guidelines to keep in mind:
- Oral diabetic medications may need dose adjustments to prevent hypoglycemia.
- Take only sips of water with oral medications, not full glasses.
- Check if iron supplements should be held 1-2 days before the MRI date.
- Consult your doctor about holding diuretics until after the scan is complete.
- Medications can usually be taken up until 2 hours before the MRI begins.
Some facilities may advise holding all oral medications starting the midnight before the scheduled MRI. Check with the scan location for their specific policies on medications and fasting.
Conclusion
An empty stomach is often recommended before an MRI exam, but may not be an absolute requirement in every situation. Typical fasting times range from 2 hours up to 8 or more hours for abdominal and pelvic scans. While fasting can be inconvenient for patients, it provides significant benefits like fewer artifacts, enhanced imaging, and reduced safety risks.
If fasting is advised for your upcoming MRI, be sure to follow all preparation instructions carefully. Drink plenty of fluids, stick to light foods, and don’t eat or drink anything for at least 2 hours beforehand. Proper planning and fasting compliance allows for the best possible MRI results during your scan.
