PET scan myths
Myth: Avoid Water — After a PET Scan
You have probably been told not to eat or drink before a PET scan. That rule ends when the scan ends. Afterwards, drinking water is not just allowed — it is recommended, because it helps clear the radiotracer from your body.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed September 2026
- Drink more, not less — Water clears the radiotracer through your kidneys and bladder. More fluid means faster clearance.
- The restriction is before the scan — Fasting before a PET scan keeps the tracer working correctly. That rule ends the moment the scan finishes.
- The tracer leaves through urine — Hydration speeds up the process. The faster it leaves, the shorter the time the tracer spends in your body.
- A few other precautions still apply — Keeping distance from pregnant women, infants, and young children for a few hours is still recommended.
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You should drink more water after a PET scan, not less. The radiotracer used in a PET scan is cleared from your body through urine. Drinking water helps it leave faster. Nuclear medicine guidelines recommend staying well hydrated in the hours after your scan.
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Is it true that you should avoid water after a PET scan?
You should avoid water for a few hours after a PET scan.
The opposite is true. Nuclear medicine guidelines recommend drinking plenty of fluids after a PET scan. Water helps your kidneys filter the radiotracer into your urine and flush it out of your body.
Drinking water will spread the radiation around inside your body.
The radiotracer is not spread by water. It is already in your bloodstream. What water does is help your kidneys clear it faster, so the total time the tracer spends in your body is shorter.
The fasting rule from before the scan applies after it too.
Fasting before a PET scan is real and important — it keeps your blood sugar stable so the tracer is taken up correctly. But that reason no longer applies once the scan is done. You can eat and drink normally afterwards.
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Why does drinking water actually help after a PET scan?
The tracer used in most PET scans — a radioactive form of glucose — leaves your body through your kidneys and bladder. Urine is the main route out.
When you drink water, your kidneys produce more urine. More urine means the tracer moves through and out of your body faster. This is why hydration is recommended, not restricted.
The confusion almost always comes from the fasting rule before the scan. That rule is real and has a specific reason. Once the scan is finished, that reason is gone.
What should you do in the hours after a PET scan?
- Drink water regularly for the rest of the dayThis is the most useful thing you can do to clear the tracer faster.
- Use the toilet normally — and flush twiceThe tracer leaves in your urine. Flushing twice is standard hygiene after a nuclear medicine procedure.
- Wash your hands after using the toiletNormal handwashing is all that is needed.
- Keep distance from pregnant women, infants, and young children for a few hoursYour radiation level after a standard PET scan is low, but these groups are more sensitive. Your nuclear medicine team will tell you how long.
- Eat normally — the fast is overThere is no food restriction after a PET scan. Eat when you are ready.
- Ask your team before breastfeedingIf you are breastfeeding, check with the nuclear medicine team before feeding your baby.
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Explore 62 more Family Support, Myths, Follow-Up and Emergencies topics
Myths & Misinformation
- Ayurvedic and Alternative Alternatives to a PET Scan
- Myth: A Normal PET Scan Means You Are Cured
- Myth: A PET Scan Can Cause Cancer
- Myth: A PET Scan Detects Every Cancer
- Myth: A PET Scan Spreads or Worsens Cancer
- Myth: A Positive PET Scan Means You Definitely Have Cancer
- Myth: A Scan From a Cheaper Centre Will Not Be Accepted
- Myth: An Expensive Scan Is Always a Better Scan
- Myth: Eating Sugar Before a Scan Will Show Up Cancer
- Myth: PET Scans Are Only for Terminal Cancer
- Myth: The Tracer Injection Is a Kind of Chemotherapy
- Myth: You Should Avoid Water After a PET Scan
- Myth: You Should Get a PET Scan Every Year to Be Safe
- Myth: You Stay Radioactive for Days After a PET Scan
Caretaker & Family Guide
- A Printable PET-CT Day Checklist for Families
- After the Scan: What the Family Should Know
- Collecting and Storing the Report and Images
- Coordinating a Scan for a Parent in Another City
- Explaining a Parent's Scan to Children
- Explaining the Scan to an Anxious Patient
- Getting an Elderly Parent to and From the Scan
- Helping Someone Fast Before a PET-CT
- Managing Cost and Payment as a Family
- Preparing Questions for the Post-Scan Consultation
- The Family's Complete Guide to a PET-CT Scan Day
- What the Attendant Can and Cannot Do During the Scan
Emergencies & Red Flags
- Accidental Radiation Exposure: Pregnancy Discovered After a Scan
- Breathing Difficulty During or After a Scan
- Delayed Contrast Reaction Hours After the Scan
- Emergencies Around a PET-CT Scan: What Needs Immediate Care
- Fainting or Collapse at the Scan Centre
- Low Blood Sugar (Hypoglycaemia) During Fasting
- Panic Attack During the Scan
- Severe Contrast Reaction: Recognising It
- What to Do If the Cannula Site Swells or Hurts After
- When to Call the Centre After Your Scan
Follow-Up & Surveillance Scanning
- Can You Refuse a Follow-Up PET Scan?
- Follow-Up Scanning During Long-Term Treatment
- How Often Will You Need a PET-CT After Treatment?
- Is Routine Surveillance PET Actually Recommended?
- Keeping a Personal Scan Log
- Reducing Radiation Across Years of Surveillance
- Scan-Based vs Symptom-Based Follow-Up
- Surveillance Scanning by Cancer Type: A Reference Table
- The Annual Cost of Cancer Surveillance Scanning
- Transferring Surveillance to a Centre Closer to Home
- What Happens If a Surveillance Scan Shows Something?
- When Can You Stop Having Scans?
Scanxiety & Emotional Impact
- Fear of What the Scan Will Find
- Getting Bad News From a Scan Report
- Getting Good News: Why Relief Is Complicated
- Living Between Scans: The Six-Month Rhythm
- Making the Most of Your Post-Scan Consultation
- Recurring Scanxiety in Long-Term Surveillance
- Scanxiety: The Fear Before and After a PET-CT
- Should You Look Up Your Results Online Before the Consult?
- Supporting Someone Through Scan Day
- Telling Family About Scan Results
- The Night Before a PET-CT Scan
- Waiting for PET-CT Results: How to Get Through It
- When a Patient Refuses to Have the Scan
- When to Seek Counselling Around Scans
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Common questions
Frequently asked questions
Why are you told not to drink before a PET scan but encouraged to drink after?
The restriction before the scan is about your blood sugar, not the radiation. The most common tracer is a radioactive form of glucose. If your blood sugar is high before the scan, it competes with the tracer and the images show less detail. Once the scan is finished, that reason disappears entirely. Drinking water after does not affect what was already captured — it only helps your body clear the tracer more quickly.
How much water should I drink after a PET scan?
Drink as you would on a warm day when you are trying to stay well hydrated — regularly and generously rather than a specific measured amount. The goal is to keep urinating throughout the day so the tracer is cleared steadily. If you have a kidney condition or are on a fluid restriction for another reason, ask your nuclear medicine team for guidance specific to you before the scan.
How long does the radiotracer stay in my body?
Most of the tracer used in a standard PET scan leaves your body within a few hours through urine. A small remaining amount breaks down through natural radioactive decay. By the time you go to sleep the same night, most people carry very little residual activity. Drinking water throughout the day speeds this process. Your nuclear medicine team will tell you if your specific scan used a tracer with a longer half-life.
Is it safe to be near my family after a PET scan?
For most family members, yes. The radiation level after a standard PET scan is low. The precaution is specifically for pregnant women, infants, and young children, who are more sensitive to radiation. Your nuclear medicine team will tell you how long to keep a distance — it is typically a matter of hours. You do not need to sleep in a separate room or avoid all physical contact with adults.
Can I drink tea or coffee instead of water after the scan?
Plain water is the most straightforward choice because it has no other effects on your body at a time when it is already processing the tracer. Tea and coffee are mild diuretics, which means they do increase urine output and would also help move the tracer out. If you are unsure, ask your nuclear medicine team — particularly if your scan involved a tracer other than standard FDG.