sodium iodide I 123 at a glance
Medicine class
Diagnostic radiopharmaceutical
Usual role
Thyroid scintigraphy and radioactive iodine uptake testing
Administration
Intravenous injection by authorised nuclear medicine staff
After administration
Hydration and frequent urination help reduce unnecessary radiation exposure
What is sodium iodide I 123 used for?
The selected product is licensed for diagnostic use only.
Functional or morphological assessment of the thyroid by scintigraphy
Measurement of radioactive iodine uptake by the thyroid
How does sodium iodide I 123 work?
After injection, iodide travels in the blood and is concentrated by thyroid tissue through the gland’s usual iodine-uptake pathway. Iodine-123 emits gamma radiation that can be detected externally to create images and measure uptake.
How to take sodium iodide I 123
It is injected into a vein by trained nuclear medicine staff. Follow the department’s preparation instructions. Tell staff about thyroid medicines, supplements, recent contrast scans and possible iodine exposure. Do not stop prescribed medicines unless your clinical team tells you to.
Tell staff if you are or may be pregnant, or are breastfeeding.
Drink fluids as directed and empty your bladder frequently after the examination.
Follow local instructions about temporary contact precautions after leaving.
sodium iodide I 123 side effects
Get urgent medical advice
- Hypersensitivity, including a severe allergic or anaphylactic reaction
- A small long-term risk associated with exposure to ionising radiation
sodium iodide I 123 in pregnancy
Tell the department if you are pregnant, might be pregnant or have missed a period. The procedure exposes the fetus to ionising radiation, so it should be performed in pregnancy only when essential and when the expected benefit clearly outweighs the risk. A non-ionising alternative should be considered where available.
sodium iodide I 123 while breastfeeding
Contact the nuclear medicine department before attending. If administration is necessary, breastfeeding should be interrupted temporarily and expressed milk discarded. The product-specific interruption is stated as 1.5 to 3 days; follow the department’s exact instructions before restarting.
sodium iodide I 123 interactions
Several medicines and sources of non-radioactive iodine can reduce thyroid uptake and affect test reliability. Give the specialist team a complete history of medicines, supplements and recent imaging.
Iodinated contrast media
Recent contrast-enhanced imaging can suppress iodine-123 uptake and may require rescheduling.
Iodine supplements or iodine-containing topical products
Stable iodine competes with the tracer and can reduce thyroid uptake.
Antithyroid medicines, including carbimazole and propylthiouracil
These can alter thyroid uptake and may need specialist-directed interruption before testing.
Common questions about sodium iodide I 123
Answers are fully visible for fast scanning and source review.
Is sodium iodide I 123 used to treat thyroid disease?
No. The selected product is licensed only for diagnostic thyroid imaging and uptake testing.
What can a thyroid scan show?
It can assess the thyroid’s iodine uptake, function, size, shape and position.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.