Diabetes and PET-CT
High Blood Sugar Found — Before Your First Scan
Every patient has their blood sugar checked before a PET-CT. If yours comes back high — and you had no idea — here is what the team does next, and what it means for your scan that day.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026
- It is more common than you think — Undiagnosed diabetes is regularly found for the first time at pre-scan blood tests.
- High sugar affects the scan's accuracy — The PET-CT tracer behaves like glucose. Elevated blood sugar competes with it and reduces image quality.
- The decision belongs to the medical team — Whether your scan proceeds is decided by the imaging team and your oncologist together.
- A delay is not a crisis — A short, planned delay to manage blood sugar gives a clearer, more useful result than a scan done with high glucose.
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Blood sugar is checked before every PET-CT because high glucose affects how the tracer is absorbed. If this is the first time your sugar has tested high, the imaging team will inform your treating oncologist that day. Whether the scan goes ahead depends on your reading and is decided together at the centre.
A whole-body PET-CT at CION costs from Rs 10,499 — among the lowest published prices in Hyderabad. Indicative price, as of September 2026.
What happens when my blood sugar is found high before a PET-CT?
Blood sugar is measured on arrival
Before the FDG tracer is injected, a nurse or technician checks your blood sugar with a finger-prick test. This happens for every PET-CT patient — it is not triggered by a prior diagnosis.
The result is reviewed by the imaging team
The nuclear medicine or radiology team sees the reading. If it is within the range the centre considers acceptable, the scan continues as planned. If it is above that range, the next steps begin.
Your oncologist is contacted
The imaging team does not make this decision alone. They contact your treating oncologist — or the on-call team if needed — to discuss the reading and what to do.
A decision is made for the same day
Depending on your reading and your oncologist's guidance, the team may ask you to wait briefly and retest, or to reschedule. You are told what is happening and why before you leave.
You are referred for diabetes follow-up
One high reading does not confirm diabetes. Your oncologist or their team will arrange proper follow-up — with a physician or endocrinologist — so your sugar can be assessed and managed before your next scan.
What does my blood sugar reading mean for the scan?
| Sugar finding on arrival | What it means for the scan |
|---|---|
| Within the centre's acceptable range | Injection proceeds as planned. No delay. |
| Slightly above the threshold | Team contacts your oncologist. A short wait and retest may be offered. Decision made together. |
| Well above the threshold | Scan is rescheduled. You leave with a plan for follow-up and a referral for your sugar. |
| Very high, with symptoms such as thirst, dizziness or feeling unwell | Medical review is arranged before any scan decision. Your safety comes first. |
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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Who decides if the scan can still go ahead?
Being asked to go home after travelling for a scan is genuinely difficult. That decision is never taken lightly — it is taken because a scan done with significantly elevated sugar is less informative and may need to be repeated, which costs more time in the end.
The nuclear medicine team makes the first assessment using the centre's protocol. Your oncologist is the second voice: they weigh how urgent the imaging is against the risk of a poor-quality result. If your situation is time-critical, tell your oncologist directly so they can speak to the imaging centre.
A high sugar found for the first time is also a medical finding in its own right. Your oncologist or their team will make sure it is followed up properly, not left as a footnote in a report.
What should I do before coming in for the rescheduled scan?
- Tell your treating doctor about the high reading before your next scan appointment — do not wait for them to find it in the report.
- Ask your doctor specifically when to take any blood sugar medicine on the morning of the scan. Timing varies by medication and must come from your doctor, not the imaging centre.
- Tell the booking team at the imaging centre that you were recently found to have high sugar. They will note it and may advise on fasting time.
- Fast for the full period the centre specifies. Eating — including fruit juice — raises blood sugar and shortens effective fasting time.
- If your sugar was very high at the first visit, ask your oncologist whether a blood test a day or two before is useful, so you do not travel again on a day the scan cannot go ahead.
- If you are started on any new medicine for blood sugar between now and the scan, tell both your oncologist and the imaging centre before the scan day.
PET-CT at CION starts from Rs 10,499 — among the lowest published prices in Hyderabad — across 4 partner centres in Banjara Hills, Punjagutta, Himayatnagar and Narayanaguda. Indicative price, as of September 2026.
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- 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
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- 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
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- Why You Have to Wait an Hour After the Injection
- Your PET-CT Scan Day: What Happens, Step by Step
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Common questions
Frequently asked questions
Does one high reading confirm I have diabetes?
No. A single elevated blood sugar reading — particularly under the stress of a hospital visit or an unusual fast — does not confirm diabetes. Diagnosis requires proper testing, typically a fasting blood glucose and an HbA1c, usually on more than one occasion. Your oncologist or the physician they refer you to will organise this. Do not start treating yourself based on a pre-scan reading alone.
Will I have to pay again if the scan is rescheduled because of my sugar?
Policies differ between centres and insurers. When you call to reschedule, ask the billing or front-desk team directly whether a rescheduled scan for a medical reason is treated differently from a missed appointment. Your oncologist's team can sometimes provide a letter confirming the clinical reason, which helps with insurer queries. Ask before assuming you will be charged again.
Why does blood sugar affect a PET-CT specifically?
PET-CT uses a tracer called FDG, which is a form of glucose that cancer cells absorb more than normal tissue — that uptake is what appears on the scan. When your blood sugar is elevated, your own natural glucose competes with the FDG. The tracer distributes less specifically, the images become harder to read, and the radiologist may not be able to give your oncologist a reliable report. Controlled blood sugar before the scan is part of getting an accurate result.
My scan is urgent. Can the team not just proceed anyway?
Sometimes, yes. Urgency is exactly what your oncologist weighs when the imaging team contacts them. If the clinical need to image quickly outweighs the reduction in quality, your oncologist may decide to proceed and note the limitation in the report. What the imaging team will not do is inject the tracer without that conversation. If you believe your situation is time-critical, tell your oncologist so they can speak to the imaging centre directly.
What should I tell my doctor when I call after a rescheduled scan?
Tell them the blood sugar reading the imaging centre recorded, the date and time it was taken, and how long you had fasted. Also mention any symptoms you had that day — thirst, blurred vision, unusual tiredness — as these help the doctor decide how urgently follow-up is needed. If the imaging centre gave you any advice about food or medicine before the next scan, repeat those instructions back to your oncologist so they can confirm or correct them.