Contrast Dye Safety: Gadolinium Side Effects Explained

MRI 09 October, 2026

Understanding MRI contrast agents and gadolinium

How does MRI work?

Magnetic resonance imaging (MRI) is an advanced medical imaging technique that produces highly detailed images of the inside of the body, particularly soft tissues, internal organs and bones. Unlike X rays or CT scans, MRI doesn’t use ionising radiation. Instead, the MRI scanner uses powerful magnets and radio waves to create images.

During MRI scans, magnetic fields temporarily affect tiny particles called protons in the body’s tissues. Radio wave pulses alter their position, and as they return to normal, they release energy. This energy is detected by the scanner and converted into detailed cross-sectional images, sometimes in 3D.

What is gadolinium contrast dye?

Gadolinium contrast agents are used to enhance the images created during an MRI scan. These agents change magnetic properties in the body to create brighter signals. The signals are detected by the MRI scanner and used to create clearer images.

Gadolinium is a rare earth metal. In its free form, it’s toxic to the human body. To stop its toxic effects when used as a contrast dye, it’s bound to a chelating agent. Chelation is the process that prevents heavy metals or minerals from harming the human body.

Gadolinium based contrast agents use different chelating agents. Some chelating agents have a cage-like structure, while others have open structures. They all make gadolinium generally safe to inject into blood vessels. At Vista we only use the ones that have cage-like structures (macrocylic) as these are the safest.

How is gadolinium given for MRI?

Before you have a gadolinium magnetic resonance imaging scan, your care team will explain exactly what will happen, including any risks and complications. You will be asked to sign an informed consent form before your scan.

You may be asked to change into a hospital gown and to remove any metal items from your body. When you’re ready for your scan, you’ll have a cannula placed in a vein in your arm. This is a thin, flexible plastic tube which is introduced using a fine needle. The needle is removed, allowing the cannula to be used to inject a gadolinium contrast medium into the vein.

The gadolinium contrast dye will flow through your blood. As it passes through your tissues, they will appear clearer on the MRI images created.

Your kidneys will remove the gadolinium based contrast material from your body over the next 24–48 hours via your urine. It’s important you drink plenty of water during this time.

Most common side effects of MRI contrast dye

Common side effects of gadolinium contrast dye usually go away within the first few hours or at most in 24–48 hours. Most side effects are mild and include:

A rash and/or itchy skin
Discomfort at the injection site
Feeling tired and/or warm
Headache
Nausea and/or vomiting
Skin that feels prickly, tingly or burning

MRI allergic reactions vs side effects

A side effect is an expected consequence of taking a substance. It’s predictable and is related to how the substance works. This is different to allergic reactions, which are unexpected and are triggered by the immune system overreacting to a substance.

Allergic reactions to gadolinium are rare and most reactions are easily treatable. An allergic reaction will usually occur within 15 minutes of having the injection but may occur up to several days later.

Symptoms of an allergic reaction to gadolinium include:

A rash
Dizziness
Itchy skin
Swelling, especially of the face and throat
Nausea
Vomiting

Severe reactions can lead to anaphylactic shock. This causes your blood pressure to suddenly drop and narrows your airways. This leads to difficulty breathing, wheezing or swallowing, dizziness, confusion and collapse.

Anaphylactic shock is a medical emergency and needs urgent treatment. It’s a rare consequence of having gadolinium contrast. At most, it’s estimated to happen in 1 in 200 cases when gadolinium is used during an MRI scan.

After having an MRI scan with gadolinium, your care team will ask you to remain at the scanning facility for around 15-30 minutes to monitor you for any signs of an allergic reaction.

If you’ve had an allergic reaction to other contrast agents, such iodine-based contrast used in CT scans, it doesn’t mean you’ll have a reaction to gadolinium. Please notify your care team of any allergies.

Gadolinium retention

There is evidence to suggest possible residual traces of gadolinium in the brain, bone and soft tissues, following administration of gadolinium based contrast media. This has primarily been associated with linear forms of gadolinium as opposed to acrocyclic forms, and in patients who have had repeated contrast enhanced studies. At Vista we only use macrocyclic contrast agents to reduce this risk. To date, there are no known harmful effects of this finding.

Who is at higher risk from MRI contrast agents?

Not everyone can have gadolinium magnetic resonance imaging. Some people are at higher risk of developing more serious side effects, usually due to pre-existing serious health problems.

Kidney disease and gadolinium

People who have a kidney problem may not be able to have gadolinium depending on their kidney function. This will be tested using a blood test called eGFR (estimated glomerular filtration rate). This test measures how well the kidneys filter out waste.

Poor kidney function can prevent gadolinium from being removed efficiently from your body. If you have severe kidney disease, exposure to gadolinium based contrast agents could potentially cause nephrogenic systemic fibrosis. This causes thickening and stiffening of tissues, including muscles, bones, organs and skin. This is more likely with linear contrast agents, which is another reason we only use macrocyclic contrast agents at Vista, as the cage-like structure is safer.

Pregnancy and gadolinium

It is unclear how gadolinium contrast affects unborn babies. However, to keep any potential risks to an absolute minimum, pregnant women are not advised to have gadolinium contrast dye unless it’s absolutely necessary.

A very small percentage of gadolinium has been shown to be excreted into breast milk, with absorption into the baby’s gut being minimal. Therefore, it is generally considered safe for both mother and infant to continue breastfeeding.

If you are pregnant or breastfeeding, please tell a member of staff before your scan.

Concerned about an MRI with contrast?

If you think you need an MRI scan with contrast but have concerns about side effects, find reassurance by booking a private GP consultation with one of our experienced Vista Health GPs.

Based on your medical history and health, your doctor can advise you on the risks and benefits of an MRI scan with contrast. If appropriate, they can help you book your private MRI scan at any one of our nationwide clinics.