What is a MAG3 renogram?
A MAG3 renogram is a type of scan that looks at the function of your kidneys, to show anything that may be affecting how well they’re draining into your bladder, like a blockage or narrowing.
MAG3 is the shortened name of the radioactive chemical used. It shows your kidneys more clearly on the scan.
What does it involve?
You’ll lie on a bed with a special camera above and below you.
At the start of the scan, you’ll be injected with MAG3, a radioactive fluid that travels through your blood to your kidneys. It gives out a type of radiation, which is picked up by the camera used in the scan so that the images produced show your urinary system (your kidneys, ureters and bladder) in detail.
Who is a MAG3 renogram for?
A MAG3 renogram can help your kidney doctor to plan your treatment because it gives more detailed information about the function of your kidneys than other tests such as renal CT and renal ultrasound.
Is it safe? Are there any alternatives?
The scan uses a small amount of radiation, which becomes inactive in the hours after the procedure and is passed out of your body in your urine.
The small dose of radiation may slightly raise your chance of cancer many years in the future, but we are all exposed to low levels of radiation naturally in daily life.
The risk from this test is very small, and your kidney doctor has requested it because the benefits of having the test are far greater than the risks.
There are no side effects from the scan itself.
What happens before a MAG3 renogram?
Tell the hospital staff in advance if you’re pregnant or breastfeeding as the scan may need to be delayed.
You should let the medical team know if you’re on any form of dialysis because your dialysis appointment may need to be coordinated with the scan.
You can eat and take your medicine as usual on the day of the scan.
You’ll be asked to drink plenty of fluid before you arrive for your appointment, but you don’t need a full bladder, so you can go to the toilet when you need to.
What happens during a MAG3 scan?
- You’ll meet the team carrying out the scan and can ask any questions.
- Before the scan, they will insert a small plastic tube called a cannula into a vein in your arm or hand so that injections can be given through it.
- You may have an injection of a diuretic drug, which will make you need to pass urine because it removes salt and water from your body. It takes 15 minutes to start working, and you’ll be asked to empty your bladder before you go into the room where you’re having the scan.
- You’ll lie on the imaging bed with the camera below your abdomen (or with the camera above if you’ve had a kidney transplant).
- The team will inject the radioactive fluid through the cannula and start the scan straight away. You’ll need to lie as still as possible.
- After the first set of scans, the team will take a one-minute image before and after you’ve emptied your bladder again. Sometimes, they may take another set of images after this.
- Allow 1-2 hours in the hospital.
Where will the MAG3 renogram take place?
It’s a day procedure that takes place in hospital in the radiology or X-ray department.
The scan is carried out by a team or radiographers or technologists.
What happens immediately after the procedure?
You’ll be able to leave the hospital and get back to your usual activities.
What should I expect when I get home?
Be aware you may need to go to the toilet more often because of the diuretic, but the effects should wear off after a few hours.
For the rest of the day, you should avoid extended close contact with children and anyone who may be pregnant, to reduce the risk of unnecessary radiation to babies and children.
How will I get the results?
The hospital team will produce a report based on the images, which will be sent to your kidney doctor. They will contact you to discuss results and next steps.
Is there anything else I need to know?
If possible, you should come to your appointment alone but let the hospital staff know in advance if you need to bring a caregiver with you.
Publication date: 01/2026
Review date: 01/2029