Radioactive iodine uptake
Alternative names:
iodine uptake test; RAIU
How the test is performed:
RAIU is a type of nuclear test of the thyroid (thyroid uptake). You are asked to ingest radioactive iodine (I-123 or I-131) capsules or liquid. After a time (usually 6 and 24-hours later) you must return to have the radioactivity measured. A probe (gamma probe) is placed over the thyroid gland (neck), measures the amount of radioactivity in the thyroid gland, and compares it to the original dose, reporting the result as a percent of the original dose.
How to prepare for the test:
Fast for 8 hours before the test.
Consult with the health care provider if you have a history of factors that may affect the test (see "special considerations"). The health care provider may restrict iodine and thyroid (or anti-thyroid) medications for 1 week before the test.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
There is no discomfort. You can eat beginning about 1 to 2 hours after ingesting the radioactive iodine, and you can resume a normal diet when the test is finished. For the scanning, you are asked to lie on a table while the scanner is placed over the neck. The scan takes about 30 minutes.
Why the test is performed:
This test is performed to evaluate thyroid function, particularly when blood tests of thyroid function (for example, T3 or T4 levels) have abnormal results.
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