Is It Normal to Have a Headache After an MRI?

Post-MRI headaches are common enough that researchers have specifically studied them, and they are almost always mild and short-lived. In one study of subjects scanned at a high-field-strength MRI machine, roughly half reported at least one side effect, with headache among the most frequently mentioned. The reassuring finding across the literature is that these headaches rarely signal anything worrying and usually fade within hours. But the reasons behind them are more varied than most people realize, ranging from the magnetic field itself to the noise, the contrast dye, or even skipping your morning coffee before the scan.

How Common Are Post-MRI Headaches

Pinning down an exact percentage is tricky because it depends on the scanner’s magnetic field strength, whether contrast was used, and how the study was designed. At 7 Tesla, the strongest scanners used in research settings, about 51% of subjects reported at least one side effect, though all were described as mild and none required stopping the exam.¹ In a much larger study comparing everyday clinical scanners, researchers tracked over a thousand consecutive outpatients across 3 Tesla, 1.5 Tesla, and 0.6 Tesla machines. At 3T, new-onset headache appeared in a small number of patients, alongside more frequent complaints of dizziness and vertigo.² At lower field strengths, headache reports dropped further. So while a headache after an MRI is not unusual, the chance of getting one partly depends on how powerful the scanner was.

It is worth noting that headache is already one of the most common complaints on any given day in the general population, which complicates these numbers. A person might attribute a headache to the scan that would have happened anyway. Researchers try to account for this by asking about symptoms both before and after the scan, but the overlap makes exact prevalence figures inherently fuzzy.

The Role of Magnetic Field Strength

MRI machines come in different strengths, measured in Tesla. Most hospitals use 1.5T or 3T scanners, while research centers sometimes use 7T machines. There is a clear trend: higher field strength means more reported side effects. In the study of over a thousand outpatients, new-onset symptoms occurred mainly at 3T, with a strong statistical signal for dizziness and vertigo at that strength compared to 1.5T and 0.6T.² The same study found that women were more likely to develop symptoms, accounting for about 75% of new-onset reports.

Stronger magnets create stronger forces on the ions flowing through your blood and on the vestibular system in your inner ear, which is sensitive to magnetic fields. These interactions can produce a subtle sense of motion or imbalance, and for some people that leads to headache, much the way motion sickness can. The effect is real but temporary; symptoms typically resolve within a few hours of leaving the scanner room. If you know you are being scanned at a 3T machine (which your facility can tell you) and you are prone to headaches or motion sensitivity, it may help to move your head slowly when entering and exiting the bore, since rapid movement through the fringe field at the scanner’s entrance is one of the known triggers of dizziness.

Noise as a Headache Trigger

MRI scanners are loud. The rapid switching of gradient coils during a scan produces a rhythmic knocking and buzzing that can exceed 100 decibels in some sequences, roughly the volume of a chainsaw. Hearing protection is standard procedure, but even with earplugs or headphones, the noise can be uncomfortable, especially during long scans that last 30 minutes or more. Sustained exposure to loud sound is a well-known headache trigger in the general population, and many people leave the scanner room feeling that the noise contributed to their head pain.

A Swedish survey of MRI and CT technologists who work around these machines daily found that both groups reported similar rates of headache and other neurological symptoms over the prior year, without a statistically significant difference between the two.³ CT scanners are far quieter but still involve workplace noise. The finding suggests that noise alone may not fully explain post-MRI headaches; the magnetic field itself and other factors likely contribute. Still, if you are sensitive to noise, letting the technologist know ahead of time can help. Some facilities offer noise-canceling headphones or can adjust scanning sequences to reduce the loudest pulses.

Gadolinium Contrast and Headaches

Not every MRI involves contrast dye, but when it does, the injected agent is almost always a gadolinium-based compound. Headache is one of the most frequently reported adverse reactions to gadolinium. A review of international pharmacovigilance databases found that headache was the most common symptom reported across clinical studies of gadolinium exposure, outranking skin discoloration, bone pain, and fatigue.⁴ The same review noted that headache weight was particularly high for certain gadolinium formulations, including gadobutrol and gadoterate meglumine.

For most people, a contrast-related headache is mild and clears within hours as the body filters the gadolinium out through the kidneys. But distinguishing between a headache caused by the contrast agent and one caused by the radiofrequency pulses of the scan itself is not straightforward. Researchers have specifically discussed the difficulty of telling these two sources apart, because both can produce similar transient head pain that overlaps in timing.⁵ For practical purposes, the distinction matters less to patients than to clinicians, since the management is the same either way: mild pain relief and hydration.

A small subset of patients have reported persistent symptoms after gadolinium exposure, sometimes lasting months. In one survey of 42 patients who self-identified as having gadolinium deposition disease, headaches persisted beyond three months in 29 of them.⁴ This is a contested area of medicine, and the condition remains poorly understood. If your headache developed after a contrast-enhanced MRI and has not resolved after several days, it is reasonable to bring it up with your doctor.

Fasting, Dehydration, and Caffeine Withdrawal

Sometimes the headache is not from the MRI at all. Many scanning protocols require you to fast for several hours beforehand, especially if contrast is planned or if the scan is being done in combination with another procedure. Fasting and dehydration are both well-documented headache triggers, and spending 30 to 60 minutes lying still in a confined tube on an empty stomach is a reliable recipe for head pain in susceptible people.

Caffeine withdrawal is a particularly sneaky culprit. If you are a regular coffee drinker and your appointment requires an early-morning fast, you may have gone significantly longer than usual without caffeine by the time the scan is over. A randomized controlled trial found that abruptly withdrawing caffeine from habitual consumers triggered severe migraine attacks in the majority of participants.⁶ In other words, the headache you blame on the MRI might actually be your brain protesting its missed dose of coffee. If fasting is required for your scan but you normally drink coffee first thing, ask your facility whether a small black coffee beforehand is permitted. Often it is.

Anxiety, Claustrophobia, and Stress

An MRI is not a relaxing experience. You lie still inside a narrow, noisy tunnel for what can feel like a long time, sometimes with an IV line in your arm. For people with claustrophobia or general anxiety, the psychological stress of the scan can be significant. Tension headaches are one of the body’s most common responses to sustained stress and muscle clenching, and many people unconsciously tense their jaw and neck muscles while trying to hold still in the bore.

There is also the nocebo effect to consider. If you expect the MRI to give you a headache, the probability of developing one goes up. This is not imaginary pain; it is a genuine neurological response driven by anticipation. Researchers studying adverse effects of medical procedures have consistently found that patients who are warned about specific side effects report those side effects more often, even in placebo groups. The loud, enclosed, clinical environment of an MRI scanner is perfectly designed to heighten this kind of anticipatory response.

Neck Positioning and Prolonged Immobility

During a brain or cervical spine MRI, your head is placed inside a close-fitting coil and you are asked to hold still for the entire scan, which can run anywhere from 20 minutes to over an hour. For many people, lying flat and motionless with the head in a fixed position creates tension in the muscles of the neck and the base of the skull. This kind of discomfort frequently produces a tension-type headache during or shortly after the scan.

If you already have neck problems, previous injuries, or a history of tension headaches, you may be more susceptible. Mentioning this to the technologist before the scan can sometimes help. Small adjustments to head padding and positioning, or scheduling a short break between longer sequences, can reduce the strain. Stretching your neck gently once the scan is done is also worth doing, since many people leave the scanner and immediately sit up to check their phone, compounding the neck tension rather than relieving it.

When to Pay Attention to a Post-MRI Headache

In the vast majority of cases, a headache after an MRI is benign and resolves on its own. A glass of water, a snack if you were fasting, and over-the-counter pain relief are typically all that is needed. But there are situations where a headache after an MRI deserves closer attention.

If you had a lumbar puncture (spinal tap) before the MRI, a headache that worsens when you sit or stand and improves when you lie down could be a post-lumbar-puncture headache, which is caused by low cerebrospinal fluid pressure. MRI findings in these patients can show abnormal changes in the membranes surrounding the brain, including compensatory venous expansion.⁷ This kind of headache is not caused by the MRI itself but is sometimes discovered because the MRI was ordered to investigate the symptom. It requires medical management rather than waiting it out.

Other scenarios that warrant a call to your doctor include a headache that is unusually severe compared to your normal experience, one that persists for more than 24 to 48 hours without improvement, or one accompanied by new neurological symptoms such as vision changes, confusion, or weakness. These are not typical MRI side effects and may point to an unrelated issue that happened to coincide with the scan or, in very rare cases, to a reaction that needs evaluation.

Children and MRI Side Effects

Kids often need sedation or general anesthesia for MRI scans because staying perfectly still is difficult for them. This changes the side-effect picture. In a study of 112 children who received inhalational anesthesia for brain MRI, half experienced at least one side effect in the hour after the anesthesia, including neurological symptoms such as headache and abdominal symptoms like nausea. Children aged five and older were significantly more likely to report neurological side effects than younger ones.⁸

Separating what the anesthesia caused from what the MRI caused is inherently difficult in these cases. A different study evaluating intravenous sedation with thiopental for pediatric MRI found no reported adverse effects, with all parents expressing satisfaction when surveyed the following day.⁹ The discrepancy suggests that the type of sedation matters, and that some post-scan symptoms in children are side effects of the anesthesia rather than the magnetic field. If your child complains of a headache after a sedated MRI, mild pain relief and rest are usually appropriate, but contact the anesthesia team if the headache persists beyond a few hours or is accompanied by repeated vomiting or confusion.

What MRI Workers Experience

One way to gauge whether MRI fields genuinely cause headaches is to look at the people exposed to them every day: MRI technologists. These workers step in and out of the scanner’s fringe field dozens of times per shift, and field measurements show that their peak exposure can reach roughly 42% of the main magnetic field strength, which is substantial.¹⁰ The Swedish survey mentioned earlier found that MRI technologists did report headaches over the prior year, but at rates that were not significantly different from CT technologists, who work around very different equipment.³

This is an interesting wrinkle. It could mean that the occupational stresses shared by both groups, such as shift work, screen time, and general workplace noise, contribute more to headache rates than the magnetic field alone. Or it could mean that MRI staff adapt to the fields over time. Either way, the evidence does not suggest that chronic MRI exposure causes any lasting headache disorder in workers, which is indirectly reassuring for patients who are worried about a single scan.

Practical Steps to Reduce Post-MRI Headache Risk

You cannot change the physics of the scanner, but you can address many of the modifiable triggers. A few things are worth doing before and after your scan:

Stay hydrated: Drink water in the hours leading up to your appointment unless your doctor specifically restricts fluids. Dehydration is one of the easiest headache triggers to prevent.
Ask about caffeine: If you are a regular coffee or tea drinker and your appointment is early, ask whether a small caffeinated drink is allowed before the scan. For many MRI protocols, it is.
Use the hearing protection: Always wear the earplugs or headphones the facility provides, and press them in snugly. Poorly fitted ear protection barely helps.
Speak up about positioning: If the head coil feels uncomfortable or your neck is strained, tell the technologist before the scan begins. Small padding adjustments make a real difference over a 40-minute scan.
Move slowly at the end: When the table slides you out of the bore, sit up gradually. Quick movements through the residual magnetic field near the scanner’s opening can trigger a burst of dizziness that cascades into a headache.
Eat afterward: If you have been fasting, eat something soon after the scan. Low blood sugar amplifies headache susceptibility.

None of these steps guarantee a headache-free experience, but together they address the most common non-magnetic triggers. If you have had a post-MRI headache before and are facing another scan, keeping a simple record of what you ate, drank, and felt before and after each scan can help you and your doctor figure out which trigger is most likely yours.