Good preparation makes a PET CT scan clearer and avoids repeat visits. Learn the fasting time, diet, blood sugar rules and diabetes tips.
To prepare for a PET CT scan, fast for 4 to 6 hours, drink plain water, avoid heavy exercise for 24 hours, and keep your blood sugar controlled. Tell the staff about diabetes, medicines, pregnancy and any recent surgery or treatment.
Why Does Preparation Matter?
The scan uses a tracer that behaves like sugar. If your blood sugar or insulin level is high, normal tissues may take up the tracer and cancer spots become harder to see. Hard exercise can make muscles light up. Good preparation means clearer images and a more reliable report. See what a PET CT scan is.
Time before scanWhat to doPrevious dayAvoid hard exercise. Eat a light, low-sugar dinner if advised4 to 6 hours beforeStop eating and sugary drinks. Drink plain water onlyAt the centreBlood sugar is checked, then the injection is givenAfter injectionRest quietly for about 45 to 60 minutesFasting and Diet
- Fast for 4 to 6 hours. Do not eat or drink anything except plain water.
- Avoid tea, coffee with sugar, juices, soft drinks, glucose, chewing gum and sweets.
- Some centres ask for a low-carbohydrate meal the previous evening. Follow your centre's instructions.
- Drink plenty of water, as it helps the tracer clear and improves images.
Blood Sugar and Diabetes
For most scans, blood sugar should be in a safe range, often below about 200 mg/dL, and some centres prefer lower. People with diabetes should not stop medicines on their own. Ask your doctor and the centre about insulin and tablet timing. Appointments are often planned for the morning to make fasting easier. Read PET CT for diabetic patients.
Medicines and Medical Information
- Take regular medicines with water unless told otherwise.
- Tell the staff about recent surgery, biopsy, chemotherapy, radiotherapy or infection.
- Tell them if you are pregnant or breastfeeding. See PET CT in pregnancy and breastfeeding.
- Mention any allergy, especially to contrast dye.
What to Wear and Bring
- Wear loose, comfortable clothes without metal. You may change into a gown.
- Carry old scans, reports, prescriptions and a list of medicines.
- Leave jewellery and valuables at home.
- Plan for 2 to 3 hours at the centre. Read the steps in PET CT procedure step by step.
After the Scan
You can usually eat and go home soon after. Drink extra water. For about 6 to 12 hours, your centre may advise keeping a little distance from pregnant women and infants. This is a simple precaution. See PET CT radiation and safety.
A Simple Example of a Good Preparation Day
Suppose your scan is at 10 AM. You eat a light dinner the evening before and avoid any gym session or long walk. You skip breakfast and take only plain water. You reach the centre 15 minutes early with your old reports and medicine list. You mention that you have diabetes and took your tablet as your doctor advised. The staff checks your sugar, finds it in range, and the scan proceeds smoothly. Compare this with a person who has a sweet tea at 8 AM. The sugar level may rise, the tracer may spread differently, and the scan may have to be postponed.
If you are unsure about any step, call the centre one day earlier. A short phone call can save you a second visit. You can also contact us before the day of your scan.
Frequently Asked Questions
How many hours should I fast before a PET CT scan?
Usually 4 to 6 hours. You can drink plain water.
Can I drink water before a PET CT scan?
Yes. Plain water is encouraged.
Can I drink tea or coffee?
Avoid sugar in tea or coffee. Many centres ask for plain water only, so follow their advice.
What should my blood sugar be?
Often below about 200 mg/dL, but the limit depends on the centre.
Should diabetic patients stop insulin?
Do not stop on your own. Follow your doctor and the centre's instructions.
Can I exercise before the scan?
Avoid hard exercise for 24 hours, as it can affect the images.
Can I take my regular medicines?
Usually yes, with water. Confirm with your doctor or the centre.
Can I go to work after the scan?
Most people can. Some centres suggest limited close contact with pregnant women and infants for a few hours.
What if my blood sugar is high on the day?
The scan may be delayed or rescheduled so that the images are reliable.
Book Your Test at Ganesh Diagnostic
Ganesh Diagnostic & Imaging Centre in Rohini, Delhi offers this test with trained radiology staff and clear reports. You can book an appointment online, check our branches across Delhi NCR, contact us for current rates, or explore all our services.
This article is for general information only. It does not replace advice from your doctor. Always follow your doctor's instructions for your test.
