Patient Guide · Nuclear Medicine Scan
Your doctor has ordered anuclear medicine scan.Here's what to expect.
A nuclear medicine scan is the most common way to look at how an organ is working (not just what it looks like on an X-ray or a CT). It\'s used for bone scans, heart scans, thyroid scans, kidney scans, lung scans and more. A small amount of a mildly radioactive tracer is given by injection (or occasionally by mouth), it settles in the organ your doctor wants to look at, and a special camera takes pictures. The dose is small, the tracer clears from your body in about a day, and simple precautions around family are only needed briefly. This page walks you through how to prepare, what the day feels like, and what to do afterwards.
Important: preparation varies by scan type. The instructions on your appointment letter (specific to your scan) take precedence over anything on this page. When in doubt, ring the nuclear-medicine department.
What is a nuclear medicine scan?
One isotope, many different scan types
The most commonly used medical scan tracer in the world
A nuclear medicine scan uses a small amount of a mildly radioactive material — called a tracer — that is given by injection (or occasionally by mouth). A special camera then takes pictures showing where the tracer has settled in your body. The most commonly used tracer is called technetium-99m. It's ideal for scans because it disappears from the body quickly (within about a day), gives you a small dose, and can be attached to different chemicals depending on which organ needs to be seen.
The tracer is "guided" to the organ your doctor wants to look at
The tracer can be combined with different chemicals so it travels to different organs. For example, one version travels to bone (for a bone scan), another to the heart (for a heart scan), another to the thyroid, kidneys, or lungs. Same base tracer, different partner chemical — different scan.
You are mildly radioactive — but only for a day or so
For the day of your scan and part of the next day, your body carries a small amount of radiation. By 24 hours later, it's essentially all gone. During that short period, there are a few simple precautions around young children and pregnant women — nothing complicated.
Common Tc-99m scans
Four you\'re most likely to be scheduled for
Bone scan
Ordered if your doctor wants to check for cancer spread to the bones, unexplained bone pain, a small fracture that didn't show on X-ray, or to see how bone cancer is behaving.
Typical workflow
You get an injection, then wait about 2 to 3 hours (that's the time the tracer takes to settle in your bones). Then the scan takes 20 to 40 minutes, and covers your whole body.
Heart scan
Ordered for chest pain, known heart-artery disease, or after an abnormal stress test — to see how well blood is flowing to the heart muscle at rest and during exercise.
Typical workflow
Two injections and two scans (one at rest, one after exercise). The "exercise" part is either walking on a treadmill or, if you can't exercise, a medicine that has the same effect on your heart. Total visit: 3 to 5 hours across one or two days.
Thyroid scan
Ordered to check an overactive thyroid, thyroid lumps, or how your thyroid is behaving after surgery. It shows how your thyroid is working, not just what it looks like.
Typical workflow
A small injection or oral dose, wait 20 to 30 minutes, then a 10 to 15 minute scan of your neck. Total visit under an hour.
Kidney scan
Ordered to check how well your kidneys are working, how urine is draining, or how a transplanted kidney is doing.
Typical workflow
An injection followed by a 30-minute scan while you lie still. The camera watches how the tracer moves through your kidneys.
How to prepare
The night before + the morning of
Bring your reports
Bring your referral letter, any previous scans (X-rays, CT, MRI), recent blood tests and your medicine list. The team uses these to make sense of your scan against your history.
Follow the specific instructions for YOUR scan
Different scans need different preparation. For a heart scan: no coffee, tea or chocolate for 24 hours before, no heavy meals for 3 hours before, wear comfortable clothes and shoes for walking on the treadmill. For a thyroid scan: you may need to pause thyroid medicine for 4 to 6 weeks first, and avoid iodine-rich food + CT dye. Your appointment letter will list what applies to you.
Fasting varies by scan
A heart scan usually needs 3 to 4 hours without food. Bone, thyroid and kidney scans usually don't need fasting. Check your appointment letter, or ring the department if unclear.
Pregnancy + breastfeeding
Confirm you're not pregnant (women of childbearing age may need a pregnancy test or the date of your last period). If you're breastfeeding, most scans mean pausing for anywhere from 4 to 24 hours — bring a plan for feeding your baby during that pause.
Bring loose clothing + something to keep you occupied
Some scans have a long wait between the injection and the scan itself (bone scan waits 2 to 3 hours). Bring a book, phone, snacks and water for the wait. Wear comfortable clothes without metal parts (zips, snaps) in the scan area.
Bringing someone with you
Not needed — you'll be alert and can usually drive afterwards. But nuclear medicine departments can feel unfamiliar; having a companion helps. For heart stress tests you may feel tired afterwards — helpful to have someone drive.
The scan day
Injection → wait → scan → home
- 1
Check-in + injection
You confirm your identity, pregnancy status if applicable, and any allergies. A small tube is placed in your arm and the tracer is injected — a small volume, takes seconds, may sting briefly. For some scans (thyroid), the tracer is given as an oral drink or capsule instead.
- 2
Waiting for the tracer to settle
The tracer needs time to reach the organ being scanned. Bone: 2 to 3 hours. Heart: 30 to 45 minutes. Thyroid: 20 to 30 minutes. Kidney: often the scan starts straight away. Use the wait to eat, drink or relax as instructed.
- 3
The scan itself
You lie on a table under a large flat camera that moves slowly over you. You need to stay very still (the stiller, the sharper the pictures), but you can breathe and blink normally. Scans take 10 to 40 minutes depending on the type. The camera doesn't touch you and you don't feel anything.
- 4
Quick check + you're free to go
The team looks at the images to make sure they're clear (once in a while an extra view is needed). If all is well, you're released. The full report takes 1 to 3 days and goes to the doctor who ordered the scan.
After the scan
Simple precautions for the rest of the day
Tc-99m has a 6-hour half-life — so by the day after your scan, essentially all activity is gone. During the first evening, simple precautions keep the dose to people around you well below any relevant limit.
Drink water + go to the toilet often
Drink plenty of water for the rest of the day and the next 24 hours. Use the toilet whenever you need — most of the tracer leaves your body in urine. Flush twice. Wash hands. These simple steps help the tracer clear from your body faster and reduce the small dose to your bladder.
A little distance from small children + pregnant women (for a few hours)
Keep a little distance from pregnant women and children under 2 years for the first 6 to 12 hours — the tracer is still active during that time. Not "stay away completely" — just don't sit for long with a small child on your lap or hug them at length that first evening. By the next morning, everything is back to normal.
If you're breastfeeding
Follow the pause the team gave you (anywhere from 4 to 24 hours depending on the scan). Milk you express during the pause should be thrown away (or stored to use later — the team will tell you how long). You can pump before the scan and refrigerate for use during the pause.
Airport alarms (same day + next day)
Very sensitive airport radiation alarms can pick up the tracer for up to 24 to 48 hours after your scan. If you're travelling, ask the team for a card that explains this. Carry it — most patients travel without any issue.
Call the team if…
You get a rash, itching, breathing trouble or swelling within an hour of the scan (an allergic reaction — very rare); severe pain or swelling where you had the injection; or anything else that worries you. The contact number is on your appointment letter.
Worth knowing · Supply quality
Why "generator freshness" matters for your scan
Most patients never see the physical Tc-99m generator that feeds their scan — it lives in the hospital hot lab. But two supply-side factors quietly affect scan quality + reliability. Worth knowing.
A freshly-prepared tracer means a clearer scan
Each day, hospitals prepare the tracer freshly from a small on-site source. The freshness of that preparation affects how clear the scan will be — a scan done from a freshly-prepared tracer tends to give clearer pictures. Your team plans the timing carefully, and this depends on getting a steady weekly supply from the maker.
The paperwork that makes routine scanning possible
Every batch arrives at your hospital with a certificate showing it's been checked for purity, sterility and safety, plus the paperwork from India's atomic energy regulator (AERB). This behind-the-scenes chain is what makes routine scanning predictable — you never see it, but it's what makes sure your scan can happen when it's scheduled.
Technical detail on Mo-99/Tc-99m generator supply and QC is on theclinical evidence library for your treating team.
Questions to ask your care team
Eight questions worth writing down
- ❓What type of scan am I having, and what is it looking for?
- ❓How long will I be in the department (from arrival to leaving)?
- ❓What preparation do I need for THIS scan — fasting, medicines, water?
- ❓Am I on any medicine that could interfere with the scan? Worth checking, as some medicines can affect it.
- ❓If I'm breastfeeding, do I need to pause? For how long?
- ❓Can I drive myself home afterwards?
- ❓When will the result be ready, and who will get it?
- ❓If I set off an airport alarm on my next trip — can you give me a card?