Diabetes & PET-CT
PET-CT Scan Preparation — for Diabetic Patients
High blood sugar is the most common reason a PET-CT scan cannot go ahead on the day. If you have diabetes, your preparation is different — and getting it right starts with one conversation before you book.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed September 2026
- High sugar cancels the scan — Your blood sugar is checked on arrival. If it is above the centre's threshold, you will be sent home after fasting and travelling.
- Medication timing changes — The timing of your diabetes medication on scan day is different from your usual routine. Confirm it with your doctor at booking.
- Preparation starts the day before — What you eat the evening before affects your morning blood sugar. Stable control overnight makes the fast easier to manage.
- One call prevents a wasted trip — Ask your doctor and the scan centre for specific instructions when you book. General preparation guides are not written for people with diabetes.
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If you have diabetes, you need to prepare differently for your PET-CT scan. The radioactive glucose used in the scan competes with your own blood sugar, so high glucose on arrival means the scan cannot go ahead. Your medication timing also changes, and you must confirm exact instructions with your doctor and the imaging centre when you book.
PET-CT at CION starts from Rs 10,499 — among the lowest published prices in Hyderabad, with no hidden charges. Indicative price, as of September 2026.
Why does diabetes change your PET-CT preparation?
A PET-CT scan uses a small amount of radioactive glucose — FDG — that cancer cells absorb more readily than normal tissue. When your own blood sugar is elevated, it competes with FDG and makes the scan harder to read accurately.
This is why the scan centre checks your blood glucose when you arrive. If the level is above the threshold they use, the scan cannot go ahead that day. You will be sent home — after the fast, after the journey, and after the wait.
Your diabetes medication also has to change on scan day. Some medications affect how the scan reads; others interact with the fast in ways that raise or lower your blood sugar unpredictably. The timing must be confirmed in advance, not assumed.
What preparation steps do I follow for a PET-CT scan when I have diabetes?
Confirm your instructions at booking
When you book, tell the centre and your oncologist that you have diabetes. Ask for specific instructions for your fasting period, the day before, and medication timing. Do not rely on the general preparation sheet — it is not written for diabetic patients.
Manage the evening before carefully
Eat your regular meals the day before but avoid a very large meal or unusually high-carbohydrate foods in the evening. Stable blood sugar going into your fast is easier to achieve when the day before was unremarkable.
Fast as instructed — not as you would normally
Fast from food for the number of hours your centre specified. Plain water may be permitted — confirm at booking. If you feel unwell during the fast, call the centre before deciding to eat or drink anything.
Take your diabetes medication as your doctor instructed for scan day
Do not follow your usual morning routine. Some medications need to be taken at a different time; some need to be paused entirely. Your oncologist or diabetologist should give you specific instructions at booking — follow those, not the packet directions.
Check your blood sugar before leaving home
If you have a glucometer, check your level before you travel and bring that reading with you. If your level seems unusually high, call the centre before you leave rather than arriving only to be turned away.
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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MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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What happens if your blood sugar is too high when you arrive?
If your glucose is above the centre's threshold on arrival, the scan will be rescheduled. This is one of the most common reasons diabetic patients lose a scan slot — not because anything went wrong with their cancer, but because preparation was not adjusted for their diabetes.
A rescheduled scan means another fast, another journey, and more time before your results. The way to prevent it is to get the right instructions before the day and follow them exactly.
If your sugar is only slightly above range, some centres will ask you to wait and recheck. Ask at booking whether this is an option at your centre, so you are not surprised on the day.
Did you know?
Elevated blood glucose at the time of an FDG PET-CT scan reduces image quality. When blood sugar is high, FDG uptake in tumour tissue falls relative to surrounding tissue — which can cause lesions to be missed or under-reported.
The preparation adjustments for diabetic patients exist specifically to bring glucose into the range where the scan gives reliable information. They are not a general safety precaution; they directly affect what the radiologist can see.
Source: Society of Nuclear Medicine and Molecular Imaging (SNMMI) — Guidelines on FDG PET/CT Patient Preparation
A whole-body PET-CT at CION is Rs 10,499 — among the lowest published prices in Hyderabad — with a free Rs 950 oncologist consultation to talk through your report. Indicative price, as of September 2026.
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- Your PET-CT Scan Day: What Happens, Step by Step
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Common questions
Frequently asked questions
Can I take my diabetes medication on the morning of the scan?
Not on your usual schedule — the timing on scan day is different, and depends on which medication you take and how well your diabetes is controlled. Some medications need to be taken at a different time than usual; some need to be paused entirely. This is the most important preparation question to raise with your oncologist or diabetologist when you book. Do not carry over your normal morning routine without asking.
What blood sugar level will allow my scan to go ahead?
Each imaging centre applies its own threshold, and you should ask your centre what that number is when you book. There is no single universal figure that applies across all centres and all protocols. What is consistent is that clearly elevated or uncontrolled blood sugar will prevent the scan from going ahead that day. Knowing your centre's threshold in advance is one of the most useful things you can find out at booking.
Can I drink water during the fast before a PET-CT?
Plain water is generally permitted in the hours before a PET-CT scan, but confirm this with your specific centre when you book, as instructions can vary. Sugary drinks, fruit juice, tea with sugar or milk, and sweetened dairy are not permitted. If you need to take any medication during the fast, ask whether swallowing a tablet with a small amount of water is acceptable.
I manage my diabetes with injections — is there anything extra I need to tell the centre?
Yes. Tell the centre and your oncologist at the time of booking. The timing of your last injection before the scan can affect your blood sugar level on arrival, and your doctor needs to advise on any adjustment specific to your situation. Do not change the timing or amount of your injection on the day based on general guidance — your own doctor should direct any change.
What if my blood sugar drops too low during the fast?
Treat the hypoglycaemia first — your safety comes before the scan. Once you are stable, call the scan centre to discuss whether the appointment can still go ahead or needs to be rescheduled. Most centres will prefer to reschedule than to scan you when you are unwell. Let the centre know what happened so they can help you plan the preparation differently for the next attempt.