Diagnostic Test
MAG3 Renogram
A MAG3 renogram uses a safe radioactive tracer to show how well your kidneys work and how quickly they drain. Read our patient-led guide on what to expect.
Key Takeaways
- A MAG3 renogram uses a safe radioactive tracer to show how well your kidneys work and how quickly they drain. Read our patient-led guide on what to expect.
- We offer specialist interpretation and related treatments. Book a consultation to discuss your options.
Overview
About MAG3 Renogram
A MAG3 renogram is a specialised nuclear medicine scan that evaluates the function of your kidneys and checks how efficiently urine drains from them down to your bladder.
It uses a tiny amount of a harmless radioactive liquid, called a tracer (attached to a chemical named MAG3), which travels through your blood to your kidneys. A special machine called a gamma camera then tracks the tracer's movement in real-time, mapping out exactly how well your urinary system is working. Because it specifically monitors movement and fluid flow, it gives doctors a dynamic picture that an ordinary X-ray or ultrasound simply cannot provide.
Test Information
Understanding Your Test
A detailed guide to your diagnostic procedure — from essential preparation and the purpose of the test to safety considerations and what to expect during the process.
The test takes place in a hospital's nuclear medicine department and typically lasts around 30 to 45 minutes.
When you are ready, a clinician will place a small plastic tube (cannula) into a vein in your hand or arm. You will lie down comfortably on your back on a scanning bed, and a large gamma camera will be positioned close to your stomach. The radioactive tracer is injected through the cannula, and the camera immediately begins taking a continuous series of pictures.
Halfway through the scan, you may be given a small injection of a diuretic medication (called furosemide). This encourages your kidneys to produce more urine very quickly, allowing the camera to see precisely how well your kidneys cope with a sudden flush of fluid. At the very end of the test, you will be asked to empty your bladder before a final, quick one-minute picture is taken.
The scan itself is completely painless and you will not feel the tracer moving through your body. The only minor discomfort is the quick pinprick or scratch when the cannula is inserted into your vein at the start.
If you are given the diuretic injection halfway through, you will likely feel a strong, sudden urge to pass urine. This is completely normal and shows the medicine is working perfectly; you will be able to use the toilet as soon as that specific segment of the scan is complete.
Your urologist or specialist will usually recommend a MAG3 scan if they suspect a blockage or a delay in your urinary system.
It is particularly helpful if you have been experiencing unexplained loin or side pain, repeated kidney infections, or if a previous ultrasound scan has shown a swollen kidney (a condition called hydronephrosis). The scan helps your medical team see whether a suspected blockage is a physical obstruction that requires surgical treatment, or if the urine is just moving a little slowly but otherwise draining safely.
At a glance
Preparation required
- You are free to eat food and take your usual medications normally before your appointment.
- Stay well hydrated: You will need to drink plenty of fluids (around 1 litre of water) before arriving to ensure your kidneys are working at their best.
- Wear comfortable, loose clothing with minimal metal parts (like zips or metal buttons), as you may be asked to remove metallic objects before lying on the scanner bed.
Risks or considerations
- The test uses a very small amount of radiation, which is considered completely safe and leaves your body naturally through your urine over the course of the day.
- Precautionary distance: As a standard safety measure in the UK, you should avoid close, prolonged contact with pregnant women and small children for long periods.
- Pregnancy and breastfeeding: You must inform the clinic immediately before your appointment if there is any chance you might be pregnant or if you are currently breastfeeding.
What it can help diagnose
- Blockages in the tube connecting the kidney to the bladder (such as a Pelviureteric Junction - PUJ obstruction)
- Whether one kidney is working less effectively than the other (split kidney function)
- Unexplained narrowing or structural issues inside the ureters
- How well a kidney is performing following a major surgery or a transplant
Our Commitment
Care you can trust
Every test is delivered to the same standard: senior consultants, a personalised plan, and the safety of an accredited private hospital behind you.
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Receive evidence-based treatments delivered by senior NHS consultants in a professional, specialist setting.
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A Heritage of Trust
Our partners bring decades of NHS and private experience, successfully managing thousands of patient cases.
Patient Guidance
Frequently Asked Questions
Common questions about this test and what to expect
3 questions
The scans are carefully analysed by a nuclear medicine specialist or radiologist.A detailed report is routinely sent back to your referring urology consultant within 7 to 10 working days.
Reviewed 31 May 2026
Was this helpful?
Yes, absolutely. The tracer does not make you drowsy or affect your driving ability, so you can drive yourself home and return to your normal daily routine straight away.
Reviewed 31 May 2026
Was this helpful?
No, not at all. The tracer has no side effects, will not make you feel unwell, and contains zero visible light radiation—so you will not glow! Drinking plenty of water after the scan will wash the remaining tracer out of your body quickly.
Reviewed 31 May 2026
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