How Long Does It Take For Contrast Dye To Leave The Body?

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When you’re about to undergo imaging tests like an ultrasound, X-ray, CT scan, or an MRI, contrast dye will be given to you to help these equipment produce distinct images of your tissues, organs, and/or organ systems. This will help doctors see what’s wrong with your internal system. Contrast dye can be injected on your vein, taken as a drink, and/or inserted on your rectum through a tube. It will naturally leave your system within a day or so. In some cases, you may get an allergic reaction, but you’ll feel better over time as long as you don’t have any underlying health conditions. Doctors will make sure that the procedure will outweigh the risks before they give you a contrast dye.

Have you seen an image produced by an X-ray or CT scan? Have you ever wondered how doctors can spot the area in which abnormalities in your body grow or is present? Did you also notice that the organs, blood vessels, or tissues they examine would usually be “white” in color while the rest are obscured?

Well, one thing will explain it all! It is a job done by a contrast dye, also known as contrast agent or medical contrast imaging.

What is a contrast dye?

When a doctor recommends a diagnostic test, a contrast dye is used to “contrast” or change how medical equipment interacts with the body.

Thus, it will show distinct images of the organs, tissues, nerves, bones, and/or blood vessels for doctors to clearly spot where’s or what’s causing you for your illnesses.

However, it’s not an actual dye that colors your organs or bones. It doesn’t do anything to your body but only changes how imaging tools see the inside of you.

Before your examination, doctors will administer you a specific kind of contrast dye depends on what kind of tests you need. You may take some time before the contrast dye will finally start working.

It will more likely take hours of prep-time for a 5 minute CT or MRI scan. You just have to be patient because the results of the examination are worth the wait.

Although you can choose to have no contrast dye, it will be much harder for doctors to distinguish the pictures of your body produced by the imaging tools.

The types of contrast dye

Intravenous contrast Oral contrastRectal Contrast
Administered into a vein by using a syringeTaken through drinking the solutionSmall tube injected into the rectal area
Has a watery consistencyHas a consistency like that of a milkshakeIs a clear-liquid or milky-white liquid
About 75mL-150mL is injected
Need to drink about 1L-1.5LDepends on the patient’s age and/or size
Used to enhance the images of internal organs like the heart, lungs, liver, adrenal glands, kidneys, pancreas, gallbladder, spleen, spleen, uterus, and bladder; soft tissues of the body, brain, and breastUsed to enhance the images of the gastrointestinal tractUsed to enhance images in the colon, rectum, and large intestines

Other types of contrast include gas and intrathecal contrast. Gas contrast is a type of contrast that patients inhale for a special lung and brain CT scan or a Xenon enhanced CT scan.

On the other hand, an intrathecal contrast is injected into a spinal sac which enhances the images of the spinal canal and nerves.

Iodine-based and Barium-sulfate contrast

You can tell by the name that it contains iodine chemical elements and/or barium-sulfate compounds.

These are the type of radiographic agents for use in X-ray or CT scan examinations. These materials block or limit what the imaging tools can see through your body.

As a result, areas present with these substances change how the inside of your body looks in the equipment or becomes “white” on the images it produced.

Iodine-containing contrast is usually injected in the veins or arteries within the fluid spaces of your spine or into other parts of your body.

Meanwhile, the barium-sulfate contrast dye is commonly taken as a drink and sometimes injected into the rectum.


Gadolinium-based contrast agents are commonly used for an MRI scan.

A doctor will recommend you an MRI scan for in-depth imaging of your brain, the spinal cord, part of your bones, and soft tissues in your body that ultrasound or CT scan couldn’t perceive. It is injected into your blood vessels or joints.

Gadolinium will react to the molecules inside your body and enhance the imaging it produces on the MRI scan.

Saline (salt & water) and gas contrast

If you need a sonographic examination of your heart, specifically an echocardiogram, an ultrasound-enhance contrast dye will be given to you.

This is a type of gas contrast dye that contains microbubbles with active saline solution. It is placed on a shell-like capsule and, once injected, will only reach the left and right sides of your heart for better imaging results on the area.

Although contrast dye has a risk of putting you on an allergic reaction, it still does you more good than harm.

Without it, it will be less likely feasible for doctors to know the abnormalities inside your body. That would put you at more risk of misdiagnosis and wrong treatments.

What can a contrast dye do to your body?

Here are common and mild allergic reactions from contrast dyes:

  • Mild skin rashes and itching with hives
  • Nausea and vomiting
  • Diarrhea
  • Headache

Immediately consult your doctor if you experience moderate to severe symptoms like:

  • Difficulty breathing
  • Convulsions
  • High or low blood pressure
  • Intense swelling in the throat or other body parts
  • Signs of heart attack
  • Severe skin rashes and hives

Before you sign a consent for an X-ray, ultrasound, CT scan, or MRI, you have to make sure that you tell your doctors about your medical history.

It could be your medications, allergies, or anything which will concern the procedure you’re about to get. The hospital will be very precautious in administering the contrast dye to avoid complications.

Risks in iodine-based and/or gadolinium-containing contrast dye

While contrast dye may less likely harm you in any way, some people may develop kidney diseases or cause complications in people with kidney problems. You must tell your doctor about your health conditions.

You are at greater risk of developing severe symptoms if you have the following:

When doctors know about your condition, they will evaluate the risks and benefits of you undergoing the procedures. They will give you medicines that will reduce the possibility of you developing kidney disease.

Contrast-induced Nephropathy (CIN)

If you have diabetes, a history of heart diseases, or severe kidney problems, you are at greater risk of developing contrast-induced nephropathy.

CIN will cause malfunctions in your kidney which symptoms usually occur within 48-72 hours. This rarely happens in patients receiving an iodine-based contrast dye.

However, if not given proper monitoring, it will lead to more severe kidney and heart problems. This disease won’t occur if you have mild kidney problems nor your kidneys are functioning well.

Nephrogenic System Fibrosis (NSF)

In very uncommon cases, you may develop an allergic reaction to gadolinium-based contrast agents used for MRIs. NSF may occur if you have a history of severe kidney disease.

You may experience thickening or swelling of your skin, organs, or other tissues in your body. The symptoms can develop within 24 hours or even several months later.

Prevention and Treatments

While there are still no known medications for diseases caused by contrast agents, the best thing you can do is trust your doctors. You have to communicate with them.

They will give you the best advice you could get about how you can prevent getting yourself at major risks of developing any contrast-induced diseases.

Below are some things you can do before and/or after you receive a contrast dye for a diagnostic test:

  • Tell your doctors about any occurring kidney problems. Your doctors may also test how well your kidneys are through a glomerular filtration rate (GFR) test.
  • Ask about the risks you may have to face upon doing the examination. Your doctors will evaluate the risks and benefits of what these tests may do to you. 
  • Take note of what preparations or precautions you have to follow before and/or after the procedures. Your doctor may require you to hydrate yourself. This will help you eliminate the contrast dye better.
  • Try to suggest undergoing the tests without having a contrast dye. Doctors will allow you not to have one if only feasible for the imaging tests. You may also suggest having a small dosage of such substances.
  • Consult your doctor if any severe symptoms occur after your procedures. Common symptoms for contrast-induced diseases include fatigue and/or stiffness in joints. Other symptoms include swelling, drying, and itching of your skin which turns into dark red patches and loss of appetite.

How long does a contrast dye leave your body?

If you received a contrast dye for a diagnostic test, your body naturally eliminates these substances within 24 hours.

Sometimes, it may take you a few days or weeks before the contrast dye flushes out from your body together with your urine or in your stool. As a result, you may find yourself visiting the restroom more often.

However, research hints that people who have undergone multiple imaging tests are at risk of retaining contrast dye, especially if they received gadolinium-based substances during those tests.

A small amount of the chemical substance stayed in some parts of their brain, tissues, and blood vessels. But, there’s no significant study that has proved its adverse effect on the patient.

Assuming that you have a normal renal function or your kidneys are functioning well, they will filter your blood from these chemical substances along with other toxins in your body and eliminate them as wastes.

Doctors may recommend you stay hydrated to help yourself flush these toxins out. They may also prescribe you a detoxifying solution or drugs to help your body remove the contrast dye.

Prenant women and children vs. contrast dye

Pregnant women on contrast dye

If you’re pregnant and you have to undergo an MRI scan to examine your abdomen or pelvis, there’s a very low possibility that your baby will be at risk because of the radiation.

If doctors recommend you for the test, you must comply because they will protect your baby at any cost.

Just like when foreign bodies enter your system, a contrast dye will not go through your placenta and feed into your baby.

Additionally, doctors have techniques that can lower the radiation that your womb may receive when taking a CT scan or MRI.

Breastfeeding women on contrast dye

If you’re breastfeeding and you are about to get a CT scan or other diagnostic tests, you may be given a chance to decide if you want to temporarily stop giving milk to your baby after receiving an IV contrast.

However, research states that contrast dye won’t affect your breast milk or your baby. You can opt to stop breastfeeding within 24 hours if you’re too concerned about the risks it will cause to your infant.

Children on contrast dye

Most of the time, doctors will require a sedative for children who will undergo an imaging test.

This is to make sure your kid won’t be moving as much as they tend to be more frantic or agitated during these types of medical procedures.

If your child has no health complications, they will normally excrete the contrast dye within a day or so.


Contrast dye will not cause you any harm more than the radiation you get from the imaging tools used for your diagnostic tests. You just have to prepare yourself according to what the doctors will tell you to do so.

If you experience severe allergic reactions or when unusual symptoms occur, please consult your attending physician immediately.

You can always have a say about the procedures you will undergo but, you should also trust your doctor about what they think is best for your condition.

The chemical substances used by doctors have undergone several tests so that they won’t cause adverse effects in your body. That’s probably the main reason why medical authorities have approved of its use in hospitals.

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Reana Jean Cuevas
Mabuhay! I'm Reana Jean Cuevas. A healthy body means living well with no worries-just happiness and more life adventures. Taking care of my body and well-being is an investment for my career and future. I was a volunteer at the Philippine Red Cross. I joined the training to become a first-aider and be able to provide other health and safety services in my community. I love discussing anything but mainly first-aid, home remedies, and women's health.

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