Scan preparation for family
Helping Someone — Fast Before a PET-CT
The fasting before a PET-CT is not complicated, but managing it for someone who is unwell, frightened, or diabetic takes preparation. This page is for the person doing the managing.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026
- Your job is logistics — Reading the prep sheet, clearing the kitchen, planning travel — the small things that make the fast bearable.
- Water is usually allowed — Plain water is almost always permitted. Check the prep sheet your imaging centre sends.
- Diabetic patients need advance notice — Tell the nuclear medicine team when you book, not on the day. Medication timing may need to change.
- A slip is not a disaster — Tell the team before going in. A rescheduled scan is far better than an inaccurate one.
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PET-CT requires fasting so blood glucose stays low enough for the radiotracer to work. Your job as the caretaker is to help them through that window comfortably, notice if they feel unwell, and know in advance what to do if they are diabetic or accidentally eat something.
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 help someone prepare for a PET-CT fast?
Read the prep sheet the evening before
The imaging centre sends written instructions with the exact fasting window and what is and is not allowed. Read it yourself the night before so you are not relying on memory on the day.
Plan the timing around sleep
A morning scan means the fast mostly runs overnight, which makes it much easier. An afternoon scan means planning what they can eat before the fast begins.
Keep plain water available
Plain water is almost always permitted and helps with the hunger feeling. No tea, coffee, juice, or flavoured water unless the prep sheet says otherwise.
Avoid eating in front of them
If you are at home during the fast, avoid cooking or eating nearby. It is a small thing that makes a real difference when someone is hungry and anxious.
Leave earlier than you think you need to
Rushing raises stress for everyone. Arriving calmly matters. Being late creates pressure for the patient and the imaging team alike.
Confirm diabetes or medication details when you check in
Even if you called ahead when booking, say it again on arrival. The team will measure blood glucose before the scan begins.
How do you keep a long fast manageable?
The hardest part is usually the awareness of the fast — the clock-watching, the hunger you cannot act on. Keep them occupied: a film, a conversation, a short walk if they feel well enough.
A morning appointment means they sleep through the difficult hours. That is the single biggest factor in how comfortable the experience is. If you have a choice of timing, morning is usually easier.
Remind them once — gently — that the fast protects the accuracy of the scan. A scan on an empty stomach takes one day. One that has to be repeated means another day, another journey, more waiting.
What if the person you are helping is diabetic?
Tell the nuclear medicine team when you book — not on the day of the scan. Diabetic patients may need adjusted instructions about when to take insulin or other medication, and that cannot be arranged at short notice.
Do not change any medication timing yourself. The treating team or the imaging centre will advise. Your job is to make sure that conversation happens early enough.
Blood glucose is tested at the centre before the scan. If it is too high, the scan may need to be rescheduled rather than proceed and give inaccurate results. On the day, watch for signs of low blood sugar — shakiness, sweating, unusual confusion — and tell the imaging staff immediately if you notice any.
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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Support for the person doing the caring
Practical guidance from a team that sees families through this every day.
What if they accidentally eat or drink something?
Tell the imaging centre before the scan begins. A small sip of plain water is very different from eating a meal, and the team can advise whether to continue or reschedule.
The scan works by detecting glucose activity throughout the body. Food beforehand can make normal areas appear active and make real findings harder to see. Rescheduling is the right call, not a failure.
If it happens on the way to the centre, call ahead so the team can decide with enough time rather than after you have already been waiting.
Questions families ask before the fast
Can they take their regular medicines during the fast?
Some medicines are allowed with a small sip of water; others need to be timed differently or held. The prep sheet will usually say. If it does not, call the imaging centre before the day — not on the morning of the scan, when there is less time to adjust. For insulin and diabetes medication, confirm the instructions with the treating team rather than assuming the standard advice applies.
What if they feel faint or very unwell during the fast?
Sit them down, keep them cool, and tell the imaging staff as soon as you arrive. If they feel unwell enough at home that you are genuinely concerned, call the centre before you leave. They will tell you whether to come in, wait, or seek other care. Feeling faint during a fast can happen, especially in elderly or already unwell patients, and the team has seen it before.
Can they have tea or coffee with no sugar?
Usually no, even without sugar. Tea and coffee affect metabolism in ways that can influence the scan result. Plain water is the safe option. If your prep sheet says clear fluids only, call the centre and ask whether tea qualifies, because practices differ between imaging centres and it is better to ask than assume.
What if they are very anxious about the scan, not just the fast?
Anxiety before a scan is normal and does not need to be argued away. What helps most people is knowing what to expect: an injection, a wait while the tracer distributes through the body, then lying still inside a large open ring — not an enclosed tunnel. Ask the centre whether they have a patient information sheet about the scan process, or whether someone can walk the patient through it on arrival.
Is there anything practical to bring on the day?
Bring the referral letter and any previous scan reports if you have them. Bring the prep sheet so you can confirm exactly what was and was not taken. Imaging centres are often cold — bring something warm to wear. And bring food for immediately after the scan. They will be hungry and relieved, and having something ready is a small kindness that matters.
Did you know?
The tracer used in most PET-CT scans is a form of glucose. Cancer cells absorb it faster than most normal tissue, which is how active areas show up on the scan.
Even a small rise in blood glucose before the scan competes with the tracer and makes those areas harder to see clearly. The fast is a clinical requirement, not a formality.
Source: Society of Nuclear Medicine and Molecular Imaging (SNMMI) patient preparation guidelines
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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Common questions
Frequently asked questions
Why does fasting matter so much for a PET-CT?
The radiotracer used in PET-CT behaves like glucose — it is absorbed preferentially by cells that are metabolically active, including cancer cells. If blood glucose is elevated when the tracer is injected, the two compete for absorption. Active areas become harder to detect, and normal areas can look misleadingly active. The fast brings blood glucose down to a level where the tracer can do its job. This is not an administrative rule; it directly affects what the scan can show.
Will the fast make them feel very unwell?
Most people find the fast uncomfortable — hunger, a mild headache, low energy — rather than genuinely unwell. Feeling faint is less common but can happen, particularly in elderly patients or those who are already frail. If they feel worse than uncomfortable, tell the imaging centre staff on arrival. They have seen it before and will know how to respond.
What can they eat and drink after the scan?
Once the scan is complete, they can eat and drink normally. There is no restriction on what they eat afterwards. Bring food for them — they will likely be hungry and may feel emotionally flat after the tension of the day. Drinking plenty of water after the scan is generally encouraged as it helps the body clear the tracer, but confirm the post-scan advice with your imaging centre.
What if the journey to the centre is very long and timing is difficult?
Do not break the fast without asking first. If the journey is long enough that the fasting window is genuinely difficult to manage, call the centre and explain. They may be able to adjust the appointment time or advise on what plain water alone covers for the journey. Arriving at the correct glucose level matters more than arriving exactly on time — tell them the difficulty early rather than managing it silently.
CION organised the scan — where does it actually happen?
CION coordinates PET-CT appointments with partner imaging centres rather than running scanners at CION locations. Your appointment will be at one of those partner centres. Your CION oncology team will send the referral and can answer questions about what is needed beforehand. The imaging centre itself will send the prep sheet with fasting instructions specific to their protocols — that is the document to follow on the day.