Blood sugar & PET-CT
Fasting With Diabetes — Before Your PET-CT Scan
Many people with diabetes are sent home from their PET-CT scan because their blood sugar is too high or too low on the day. That is avoidable — but it requires a conversation with your doctor before you travel.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed September 2026
- Plan before scan day — Blood sugar levels that are too high or too low will cancel the scan. Planning in advance means this does not happen after you have already travelled.
- Medicines need timing guidance — Some diabetes medicines lower blood sugar even without food. Your doctor must advise on whether and when to take them on scan day.
- Bring glucose with you — A glucose tablet or sugary drink in your bag is a simple precaution that protects you during the fasting period.
- Tell the scan team on arrival — The radiographer needs to know you have diabetes before the scan starts, not after a problem occurs.
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Fasting before a PET-CT scan is safe for most people with diabetes, but it cannot be done the same way as fasting without diabetes. Some medicines lower blood sugar even without food, so your treating doctor must advise on medicine timing before scan day. Tell your scan centre you have diabetes when you book.
CION offers PET-CT in Hyderabad from Rs 10,499 — among the lowest published prices in the city, with no hidden charges. Indicative price, as of September 2026.
How do you fast safely with diabetes before a PET-CT?
Tell the scan centre about your diabetes when you book
The centre needs to know so they can give you the right instructions. Ask specifically whether they have a protocol for patients with diabetes, and what time slot works around your medicine schedule.
Ask your treating doctor about your diabetes medicines on scan day
Some medicines lower blood sugar even when you are not eating. Your doctor will tell you whether to adjust the timing of your medicines on scan day. Do not make this decision yourself, and do not simply skip a dose without guidance.
Check your blood sugar before leaving home
A reading before you travel tells you whether it is safe to proceed. If your reading is outside the range your doctor has advised, call the scan centre before travelling rather than arriving and being turned away.
Bring fast-acting glucose for the journey and the wait
Carry glucose tablets, a small juice, or another fast-acting sugar your doctor has suggested. Keep it in your hand or pocket, not in a bag you hand in on arrival.
Tell the radiographer you have diabetes as soon as you arrive
Tell the team on arrival, not only if you feel unwell. This lets them monitor you appropriately and act quickly if something changes during the scan.
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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What warning signs should you watch for during the fast?
| Sign | What it may mean | What to do right now |
|---|---|---|
| Shaking, sweating, or feeling anxious | Blood sugar has dropped | Take glucose immediately and tell the scan centre staff |
| Extreme hunger or light-headedness | Blood sugar may be falling | Tell the radiographer before the scan begins — do not wait |
| Confusion or difficulty speaking | Severe blood sugar drop | This is an emergency — call for help from whoever is with you |
| Cannot be roused or loses consciousness | Dangerous blood sugar drop | Call 108 immediately — do not wait |
| Blood sugar too high to scan on arrival | Scan must be postponed | Ask your team when to rebook and what to change before that date |
| Typically starts | During the fasting period, often in the hour before the appointment | Symptoms can come on quickly — do not wait to see if they settle on their own |
What should you prepare before scan day?
- Tell the scan centre you have diabetes when you book, not on the morning of the scan
- Ask your treating doctor whether to adjust the timing of your diabetes medicines on scan day
- Confirm medicine timing with both your doctor and the scan centre before the scan date
- Check your blood sugar before leaving home on scan day
- Bring a fast-acting sugar — glucose tablets or a small juice — and keep it easy to reach
- Bring a written list of your current medicines to show the scan team on arrival
- Tell the radiographer you have diabetes as soon as you arrive
Book a PET-CT at CION from Rs 10,499 — among the lowest published prices in Hyderabad — with an oncologist-reviewed report and a free Rs 950 consultation, across 4 partner centres. Indicative price, as of September 2026.
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Common questions
Frequently asked questions
Is a six-hour fast safe if I have diabetes?
For most people with well-managed diabetes, a six-hour fast before a PET-CT scan is safe when it is planned in advance. The risk is not the fast itself but taking medicines that lower blood sugar while you are not eating. Your treating doctor will advise whether to adjust your medicine timing. If you follow that guidance, check your blood sugar before leaving home, and bring fast-acting glucose, the fast is manageable for most people. If you are unsure at any point, call your doctor rather than making the decision yourself.
Can I take my diabetes medicine before the scan?
That depends on which medicine you take and when your scan is scheduled — and it is a question only your treating doctor can answer. Some medicines lower blood sugar even without food, and taking them during a fast can cause a dangerous drop. Others are safer to continue. Do not guess, and do not simply skip a dose without guidance either, as that can push blood sugar in the other direction. Confirm the plan with your doctor before scan day, and tell the scan centre at booking that you are on diabetes medicines.
What happens if my blood sugar is too high when I arrive?
If your blood sugar is above the level needed for a reliable result, the scan will be rescheduled. The radiotracer used in a PET-CT scan competes with glucose in your blood, so a high reading makes the images less accurate and can lead to a result that does not reflect your true situation. This is one of the most common reasons for a cancellation on the day, and it is avoidable. Ask your treating doctor what blood sugar level is acceptable before your scan, and check your reading before you travel.
Can I drink water during the fast?
Plain water is generally permitted and encouraged during the fasting period. Staying hydrated helps the scan run smoothly. The restriction is on food, sugary drinks, and anything that raises blood sugar — including sweetened tea, coffee with milk, or fruit juice. Confirm this with your scan centre when you book, as the guidance for your specific scan may differ slightly. If you need to take a medicine with a small sip of water, ask whether that is acceptable when you confirm your preparation instructions.
What if I feel unwell during the scan?
Tell the radiographer immediately — do not try to wait out the scan if you feel unwell. Scan rooms have a communication system so you can speak to the team during the procedure. If you feel shaky, sweaty, confused, or faint at any point, say so right away. The team will stop the scan and assess you. If you are travelling alone, tell the scan centre when you arrive so they know to check on you. Feeling unwell during a fast is not unusual for someone with diabetes, and the team is trained to manage it.