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Iodine 123 Whole Body (N123W)

Patient information A-Z

Appointment card
Day Date Appointment time
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Please complete your appointment details FROM YOUR APPOINTMENT LETTER and bring this leaflet with you.

What is ‘nuclear medicine?’

Nuclear medicine refers to the medical use of radioactive tracers for the diagnosis and sometimes treatment, of medical conditions.

Nuclear medicine tests are helpful to diagnose a wide variety of illnesses. The clinician that referred you to nuclear medicine will have already explained to you the reasons for having this test.

This leaflet is to explain your scan and provide you with some general information. The procedure will be fully explained to you when you attend. We are happy to provide additional information before hand and our contact details are on the back of this leaflet.

Benefits of nuclear medicine tests and are they dangerous?

Nuclear medicine procedures are commonly used diagnostic tools that utilise ionising radiation to obtain important clinical information.

There are small risks associated with the use of ionising radiation. Ionising radiation can cause cell damage that can, after many years or decades, contribute to the development of cancerous cells. This procedure carries only a very small chance of this happening to you.

Your doctor will have considered the risk and benefits of having the test before referring you to us. The benefits of the test outweigh the potential risk.

Will it hurt?

No. There are no side effects from the tracer and no restrictions following the test. You will be able to continue with your usual daily activities.

What is an Iodine 123 Whole body scan?

This test allows us to identify and localise ectopic thyroid tissue within your body.

Do I need to prepare for the test?

  • YES. A low iodine diet should be followed for two weeks prior to your test.
  • Do not eat seafood or take any fish oil capsules, kelp/seaweed supplements or multi vitamins containing iodine for 1 week before the test.
  • You will need to fast for 4 hours before your test. This includes no liquids for 1 hour prior to your test.

  • If you are diabetic please bring your medication with you.
  • Please contact our department if you have received any x-ray contrast material within 3 weeks of your test, or if you are taking any medication for your thyroid.

How is the test carried out?

This test is a two day protocol.

DAY 1: On arrival you will be given a drink, containing a small amount of radioactive material to swallow.

After your drink you will be able to leave the department, returning the next day for your scan. You will be given a time for this scan before you receive the drink.

DAY 2: When you return we will image your whole body. The images are taken with you lying on a bed where you will need to lie still for up to 30 minutes. We can usually take your pictures without removing clothing.

Occasionally we need to perform an additional SPECT/CT scan but we will not be able to confirm this until after your first image. If the SPECT/CT is required you will need to lie still for up to an additional 45 minutes.

How long will the test take?

DAY 1: Up to 30 minutes.

DAY 2: Up to 2 hours.

What if I am pregnant or breastfeeding?

It is usual to avoid radioactive tests during pregnancy. Small amounts of some radioactive substances may appear in breast milk. Patients who are breast feeding and those that know, or suspect that they are pregnant should contact the department before attending to discuss this further and should also inform the department upon arrival.

What happens after the test?

You are free to go home or return to your ward. There are no restrictions following this test. Your results will be reported and available from your referring clinician/ team or GP within 3 weeks after your appointment.


Due to the small size of the waiting area in Nuclear Medicine we ask that you please limit the number of people accompanying you for your visit.

Travelling abroad?

Please be aware that most airports have sensitive radiation monitors which detect very small amounts of radiation and may detect a residue trace from your test. We advise you keep and travel with your appointment letter if you are travelling within the next few days.

How to find/contact the department:

The Nuclear Medicine department is located on level 3, in the outpatient end of the hospital. If you have any queries or cannot make your appointment please contact the department as soon as possible on 01223 217145.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151