An MRI can indeed cause people to feel sick, a phenomenon that is usually temporary and arises from a combination of the machine’s physical characteristics, psychological factors, and sometimes the use of contrast agents. Magnetic Resonance Imaging (MRI) uses a powerful magnetic field and radio waves to create detailed internal images of the body. Unlike X-rays or CT scans, this procedure does not use ionizing radiation, but its unique operating environment can still lead to feelings of discomfort or malaise. The experience of feeling unwell stems from several distinct mechanisms related to the procedure.
Physical Sensations from the MRI Machine
The most immediate physical discomfort comes from the extreme noise generated during the scanning process. The loud thumping, banging, and knocking sounds are produced by the rapid electrical current switching within the gradient coils, which are essential for creating the images. These noises can reach sound pressure levels well over 100 decibels, comparable to a jackhammer or a rock concert. Even with mandatory ear protection, this intense acoustic vibration can induce stress, headaches, and a general feeling of unease.
The powerful static and gradient magnetic fields can directly interact with the body’s balance system. The inner ear, specifically the labyrinth, contains fluid rich in charged ions that helps the body sense motion and maintain balance. The magnetic field exerts a force (Lorentz force) on this electrically charged fluid, which stimulates the hair cells responsible for motion sensing. This stimulation can incorrectly signal movement to the brain, resulting in temporary dizziness, vertigo, or a subtle sensation of free-falling, all of which are closely linked to nausea.
Magnetic-field-induced vertigo is more common in newer, high-strength MRI systems, such as 7-Tesla scanners. Up to 25% of patients may experience these symptoms, especially when the patient table moves. The radiofrequency energy used by the machine can also cause a slight warming of the body tissue. In sensitive individuals or during long scans, this mild thermal effect can add to the feeling of general malaise or discomfort.
Psychological Symptoms and Claustrophobia
Beyond the direct physical effects of the machine, the confined environment can trigger significant psychological distress that manifests as physical sickness. The MRI machine is a narrow, tube-like structure. The need to remain perfectly still inside this small space for an extended time is a common source of anxiety, often leading to claustrophobia, which is one of the most frequently reported causes of distress during an MRI.
The psychological stress of being enclosed can rapidly escalate into a panic attack, leading to a host of physical symptoms that mimic or induce sickness. Symptoms like hyperventilation, a rapid heart rate, and intense fear can directly trigger nausea, lightheadedness, and stomach upset. Furthermore, some individuals experience anticipatory anxiety, where worry about the upcoming procedure begins hours or even days before the scan. This high level of pre-procedure stress can cause genuine physical symptoms like tension headaches or gastrointestinal distress.
Adverse Reactions to Contrast Dyes
In many MRI exams, a Gadolinium-based contrast agent (GBCA) is injected intravenously to improve image clarity. While generally considered safe, these agents can induce side effects in a small percentage of patients. The most common mild, non-allergic reactions often include transient symptoms such as a temporary metallic taste in the mouth or a cold sensation at the injection site.
Nausea and sometimes vomiting are frequent acute adverse effects associated with GBCA injection, though the overall incidence of any acute reaction is low, occurring in less than 1% of patients. These mild reactions are often temporary and resolve quickly without intervention. In very rare instances, a true allergic or hypersensitivity reaction may occur, which can range from mild effects like a rash or hives to more severe symptoms like swelling or respiratory distress.
Tips for a More Comfortable Scan
Taking proactive steps before and during the examination can significantly reduce the likelihood of feeling unwell. Patients who experience anxiety or claustrophobia should discuss these concerns with their healthcare provider beforehand to explore options like open MRI machines or conscious sedation. Eating only a light meal before the scan can help minimize the potential for nausea, especially if a contrast agent is administered.
During the procedure, utilizing the provided earplugs or headphones is important for mitigating the intense acoustic noise that contributes to stress and headaches. Focusing on slow, deep, controlled breathing techniques can help manage anxiety and prevent hyperventilation. Patients should always be aware of the call button and use it to alert the technologist if they experience significant discomfort or distress. After the examination, increasing fluid intake helps the body flush out any residual contrast agent, aiding in resolving lingering mild side effects.