Before your PET scan
Low Blood Sugar During — PET Scan Fasting
If you are diabetic and fasting before a PET scan, low blood sugar is a real risk during the wait — especially if you have taken insulin or blood-sugar-lowering tablets this morning. Shakiness, sweating, dizziness or confusion during the fast means telling staff immediately, not waiting for your scan.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed September 2026
- Diabetics carry higher risk — If you take insulin or certain tablets, fasting removes the food that keeps your blood sugar stable.
- Symptoms can come on quickly — Low blood sugar can progress from mild shakiness to confusion or loss of consciousness within minutes.
- Tell your team before the day — Appointment timing and medication plans can be adjusted — but only if your team knows in advance.
- Never push through symptoms — Feeling unwell during the fast is not a reason to stay quiet — tell the staff immediately.
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Low blood sugar during the PET scan fast is a specific risk for diabetics, particularly those on insulin or tablets that stimulate insulin. If you feel shaky, sweaty, dizzy or confused during the wait, tell the imaging centre staff immediately. Do not wait for your scan slot. Severe symptoms — confusion, loss of consciousness — need emergency care now.
If a symptom below applies to you, do not wait for a callback. Call 1800-202-8726 or go to your nearest emergency department.
How do you tell mild symptoms from a dangerous episode?
| Sign | Mild — tell staff immediately | Severe — emergency care now |
|---|---|---|
| Shakiness or trembling | Noticeable, but you can still speak and move | Uncontrollable, spreading to your whole body |
| Sweating | Cold, clammy skin | Heavy sweating alongside confusion or pallor |
| Mental clarity | Anxious and foggy but aware you feel unwell | Confused, cannot answer simple questions, disoriented |
| Ability to stand | Unsteady but upright | Cannot stand or about to faint |
| Typically starts | Any point during the fast; sooner if insulin or stimulating tablets were taken that morning | Rapidly if mild symptoms are not reported to staff and acted on |
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(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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What should you do before the scan if you have diabetes?
- Tell the imaging centre you have diabetes when you book — not on the day of the scan.
- Ask your oncologist or diabetologist whether to adjust your medication before the fast.
- Do not take insulin or tablets that stimulate insulin without specific advice for scan day.
- Bring any emergency glucose your team has recommended — gel, tablets, or a sugary drink.
- Tell staff when you arrive that you are diabetic and have been fasting.
- Do not drive yourself to the scan if you are on insulin or blood-sugar-lowering medication.
Why does your team need to know about your diabetes before the scan?
Your team needs to know because the fasting period removes the food that normally keeps blood sugar stable — and if you are on insulin or certain tablets, your levels can drop further during the wait than they would in someone without diabetes.
Your oncologist and the imaging centre can plan around this by scheduling you earlier in the day, adjusting your medication, or checking your blood sugar before the scan begins. None of this can happen if they do not know.
Tell three people: your oncologist when fasting is first discussed, the imaging centre when you book, and the staff again when you arrive. If you feel unwell at any point during the wait, tell staff immediately — do not stay quiet to avoid disrupting the schedule.
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.
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- 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
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Common questions
Frequently asked questions
Do I have to fast if I have diabetes?
Yes. Fasting is required because elevated blood sugar makes the PET images unreliable — glucose competes with the radiotracer the scan uses. Being diabetic changes how the fast is managed, not whether you fast. Your team may schedule you earlier in the day, adjust your medication, or check your blood sugar before starting. Ask for a specific plan well before the day.
Should I take my diabetes medication on the morning of the scan?
This depends entirely on what you take. Insulin and some tablets that stimulate insulin production carry a real risk of low blood sugar if taken without food. Other types of diabetes medication carry a different risk profile during a short fast. Your oncologist or diabetologist should give you specific instructions before the day. If you have not received them, call before the scan — do not assume your usual routine applies.
What happens to the scan if my blood sugar drops too low?
The scan will be paused or postponed while you are stabilised. This is the right outcome — proceeding while you are unwell is unsafe, and the images would be unreliable in any case. The imaging team checks your blood sugar before starting; if it falls outside the range needed for a valid result, they will advise on next steps. This is the system working correctly, not a failure.
Who should I tell about my diabetes, and when?
Tell three people: your oncologist when fasting is first discussed, the imaging centre when you book, and the staff when you arrive on the day. If you feel unwell during the wait — shaky, sweaty, dizzy, or confused — tell the staff immediately, before the scan begins. A note in your file is not a substitute for telling the person in front of you on the day.