Preparing for your scan
Can I Drink Water — Before a PET-CT Scan?
Yes — plain water is not just allowed before a PET-CT scan, your team wants you to drink it freely. But tea, coffee and juice are not allowed, even in small amounts. Getting this wrong can mean your scan has to be rescheduled.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed September 2026
- Water is safe — Plain water does not affect blood sugar and can be drunk freely during the fasting period.
- Tea and coffee are not — Even black, unsweetened tea or coffee can affect the scan — leave both out entirely.
- Juice counts as food — Fruit juice raises blood sugar just as food does. It is not allowed during the fasting period.
- Getting it wrong wastes the scan — A raised blood sugar at scan time can reduce accuracy enough that the scan needs to be repeated on a different day.
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Yes — plain water is allowed and encouraged before a PET-CT scan. Tea, coffee, fruit juice, milk and soft drinks are not allowed. They raise blood sugar or stimulate metabolism, which interferes with the radiotracer. Drink plain water freely right up to your appointment time.
CION's PET-CT scans in Hyderabad start at Rs 10,499 — among the lowest published prices in the city, with no hidden charges. Indicative price, as of September 2026.
Which drinks are allowed before a PET-CT scan?
| Drink | Allowed before the scan? | Why |
|---|---|---|
| Plain water | Yes — drink freely | Does not affect blood sugar or the tracer |
| Tea or coffee (black, no sugar) | No | Stimulates metabolism and can affect how the tracer is distributed |
| Tea or coffee with milk or sugar | No | Sugar raises blood glucose; milk contains lactose, which is also a sugar |
| Fruit juice | No | High in natural sugar — disrupts the scan |
| Soft drinks and energy drinks | No | Sugar and stimulants affect blood glucose |
| Alcohol | No | Alters metabolism and causes dehydration, reducing scan quality |
What should you do in the hours before your PET-CT scan?
Note your fasting start time
Your centre will tell you at booking when to stop eating and drinking. Everything except plain water stops at that point. Write it down so there is no confusion on the day.
Drink plain water during the fast
Water is not just permitted — your team wants you hydrated. Your centre will advise how much to aim for. Drink steadily through the fasting period rather than trying to catch up just before you leave.
Stop all other drinks from the fasting time
Tea, coffee, juice and milk all stop when the fast starts. If you usually have tea with breakfast, plan ahead so the habit does not catch you out on the morning of the scan.
Continue drinking water until you arrive
You do not need to stop water at any point before the scan. Arriving well-hydrated helps the scan and makes the injection easier.
Tell your team if anything went wrong
If you accidentally drank juice or ate something, say so on arrival. Do not skip the appointment without speaking to the team first — they will advise whether to proceed or reschedule.
PET-CT Partner Centres
PET-CT Scan Centres in Hyderabad
CION offers PET-CT scans through 4 trusted partner PET-CT centres across Hyderabad, so you can choose the one closest to you. Call 18002028726 and we’ll guide you to the earliest available appointment.
PET-CT Centre — Punjagutta
PET-CT Centre — Himayatnagar
PET-CT Centre — Narayanaguda
These are partner diagnostic centres within the CION network. Toll-free booking: 18002028726.
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Why does what you drink affect the scan?
The radiotracer used in a PET-CT scan is a sugar-like compound. Your body moves it through tissues the same way it moves glucose — which is exactly what the scanner is measuring.
If your blood sugar is raised when the scan happens, your body uses its own glucose rather than taking up the tracer evenly. The result is a scan that is harder to read accurately, and sometimes one that cannot be used at all.
Plain water contains no sugar and has no effect on blood glucose, which is why it is the one drink that stays open throughout the fasting period. Everything else — including drinks that feel harmless, like black tea — is excluded because it changes how your metabolism behaves during the scan window.
If you have diabetes or a kidney condition, your treating team will give you specific instructions about fasting and your medicines. Follow their guidance rather than the general preparation instructions on this page.
Did you know?
A single sugary drink taken during the fasting period can raise blood glucose enough to reduce the quality of a PET-CT scan — sometimes to the point where it needs to be rescheduled on a different day.
Drinking plain water, by contrast, actively helps: it flushes the radiotracer through the kidneys and reduces background signal in the images.
Source: European Association of Nuclear Medicine (EANM) guidelines on FDG PET/CT preparation
CION does PET-CT in Hyderabad from Rs 10,499 — among the lowest published prices in the city — including an oncologist-reviewed report and a free Rs 950 consultation. Indicative price, as of September 2026.
Explore 92 more Preparing For and Having Your Scan Safely topics
Preparing for Your Scan
- A Printable PET-CT Preparation Card
- Can I Drink Water Before a PET-CT Scan?
- Can I Have a PET-CT Scan During My Period?
- Can I Take My Regular Medicines Before a PET-CT Scan?
- Can You Reschedule a PET-CT Scan?
- Cold Weather, Shivering and Brown Fat: Why You Are Asked to Stay Warm
- Fasting Before a PET-CT Scan: How Long and Why
- How to Prepare for a PET-CT Scan: The Complete Checklist
- Preparing a Very Elderly or Frail Person for a PET-CT
- Preparing a Wheelchair-Bound or Bedridden Patient
- Preparing for a PSMA, DOTATATE or FAPI PET-CT
- Should I Avoid Exercise Before a PET-CT Scan?
- Smoking, Alcohol and Caffeine Before a PET-CT Scan
- What Happens If You Break the Fast by Mistake?
- What to Carry to Your PET-CT Appointment
- What to Eat the Day Before a PET-CT Scan
- What to Wear to a PET-CT Scan
- Why Your Kidney Function Test Is Needed Before a PET-CT
Contrast, Cannula & Procedure Safety
- Can You Have a PET-CT If You Are on Blood Thinners?
- Can You Have a PET-CT Through a Port or PICC Line?
- Contrast Allergy and PET-CT: What to Declare
- Contrast Reaction Symptoms: What to Watch For
- Contrast and Kidney Function: The Creatinine Rule
- Infection Risk and Hygiene at a Scan Centre
- Is Contrast Used in a PET-CT Scan?
- Metformin and Contrast: What Is the Rule?
- Side Effects of a PET-CT Scan
- The Cannula: Bruising, Pain and Difficult Veins
- Tracer Leakage at the Injection Site (Extravasation)
- What If You Feel Unwell During the Scan?
Diabetes & Blood Sugar for PET-CT
- A Diabetic Patient's PET-CT Day Plan
- Best Appointment Time for a Diabetic PET Scan
- Can Diabetics Take Their Tablets Before a PET Scan?
- Does Diabetes Change Your SUV Reading?
- Fasting Safely With Diabetes Before a Scan
- Insulin and PET-CT: Timing Rules
- Newly Diagnosed Diabetes Found Before a Scan
- PET-CT Scan With Diabetes: The Complete Preparation Guide
- PET-CT With Steroid-Induced High Sugars
- What Blood Sugar Level Is Needed for a PET-CT Scan?
- What Happens If Your Sugar Is High on the Day?
- What to Eat the Day Before if You Have Diabetes
Radiation Safety & After-Scan Precautions
- Are You Radioactive After a PET-CT Scan?
- Being Around Pregnant Women After a PET-CT Scan
- Can I Hold My Child or Grandchild After a PET-CT Scan?
- Can a PET-CT Scan Cause Cancer?
- Cumulative Radiation From Repeated Scans
- Do You Need Precautions After a PSMA or DOTATATE Scan?
- Do You Need Separate Utensils or a Separate Toilet After a PET-CT?
- How Long Does the Tracer Stay in Your Body?
- How Long Should You Avoid Close Contact After a PET-CT?
- How Many PET-CT Scans Are Safe in a Year?
- How Much Radiation Is in a PET-CT Scan?
- Is PET-CT Radiation Different From Radiotherapy?
- Is the Radiation From a PET-CT Scan Dangerous?
- PET-CT Radiation Compared With CT, X-Ray and Natural Background
- Radiation Safety at Home After Your Scan: A Family Checklist
- Radiation Safety for Staff and Attendants at the Centre
- Simple Steps to Clear the Tracer Faster
- Travelling Home After a PET-CT Scan: Public Transport and Airports
Scan Day: What Actually Happens
- Can Someone Stay With Me During the Scan?
- Can You Drive Yourself Home After a PET-CT Scan?
- Can You Have Sedation for a PET-CT Scan?
- Can a PET-CT Scan Be Done on the Same Day as Other Tests?
- Contrast in a PET-CT Scan: When It Is Used and Why
- Eating and Drinking After Your PET-CT Scan
- How Long Does a PET-CT Scan Take?
- Is a PET-CT Scan Painful?
- Is a PET-CT Scanner Closed Like an MRI? Claustrophobia Explained
- The Tracer Injection: Does It Hurt?
- What Happens If the Scan Cannot Be Completed?
- What If You Cannot Lie Still or Have Tremors?
- What to Expect Immediately After the Scan
- Why Was My Scan Repeated or Extended on the Day?
- Why You Have to Wait an Hour After the Injection
- Your PET-CT Scan Day: What Happens, Step by Step
Special Populations
- Breastfeeding and PET-CT: How Long to Pause
- PET-CT Scans for Children: A Parent's Guide
- PET-CT With Kidney Disease or on Dialysis
- PET-CT With a Pacemaker, Stent or Metal Implant
- PET-CT for Claustrophobic Patients
- PET-CT for Patients Who Cannot Lie Flat
- PET-CT for Patients With Anxiety or Panic Disorder
- PET-CT for Patients With Dementia or Confusion
- PET-CT for Patients With Incontinence or a Catheter
- PET-CT for Patients With a Stoma
- PET-CT for Patients on Long-Term Steroids
- PET-CT for Very Elderly or Frail Patients
- PET-CT for Very Heavy Patients: Weight and Bore Limits
- PET-CT for Wheelchair and Bedbound Patients
- PET-CT in Pregnancy: Why It Is Avoided
- Sedation and Fasting for a Child's PET Scan
Your next step
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Common questions
Frequently asked questions
How much water should I drink before a PET-CT scan?
Your centre will give you a specific amount to aim for at booking — follow that guidance rather than a general figure. As a direction of travel, your team wants you well-hydrated on arrival. Drink steadily through the fasting period rather than trying to catch up just before you leave. If you have a kidney condition or have been told to restrict fluids for any reason, ask your treating team before the scan what rule applies to you.
Can I have black tea or black coffee with no sugar before a PET-CT?
No. Even black, unsweetened tea and coffee are not allowed during the fasting period. They contain compounds — including caffeine — that stimulate metabolism and can affect how the radiotracer is distributed in the body. The result can be a scan that is harder to interpret accurately. Plain water is the only drink that is safe during the fasting window.
What happens if I accidentally drink juice or eat something before the scan?
Tell the team at the centre as soon as you arrive. Do not try to hide it or delay the appointment without speaking to them first. Whether the scan can go ahead depends on what you ate or drank, how much, and how long ago. Sometimes it can proceed; sometimes it is better to reschedule. The team needs accurate information to make that call safely, and rescheduling is far better than a scan that cannot be relied on.
I have diabetes — are the preparation rules different for me?
The water rule is the same: plain water is allowed. But fasting with diabetes needs careful management, and your treating oncologist or the scan centre must give you specific instructions before the day. Do not follow standard general fasting guidance — your team needs to advise based on how your diabetes is managed and what medicines you take. This is one of the most important questions to ask at booking.
Can I take my regular medicines with a sip of water before the scan?
This depends on the medicine. Some are fine to take with water before a PET-CT scan; others should be held. Your treating oncologist and the scan centre need to advise on this specifically — it is one of the questions to ask at booking, not something to decide on the morning. Do not stop or take any medicine based on this page alone, as both taking a medicine that should have been held and holding one that should have been taken can affect the scan or your health.