BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuRadioactive iodine uptakeThyroid uptake; Iodine uptake test; RAIURadioactive iodine uptake (RAIU) tests thyroid function. It measures how much radioactive iodine is taken up by your thyroid gland in a certain time period.A similar test is the thyroid scan. The 2 tests are commonly performed together, but they can be done separately.Thyroid scanA thyroid scan uses a radioactive iodine tracer to examine the structure and function of the thyroid gland. This test is often done together with a ...ImageRead Article Now Book Mark Article How the Test is Performed The test is done in this way:You are given a pill that contains a tiny amount of radioactive iodine. After swallowing it, you wait as the iodine collects in the thyroid. The first uptake is usually done 4 to 6 hours after you take the iodine pill. Another uptake is usually done 24 hours later. During the uptake, you lie on your back on a table. A device called a gamma probe is moved back and forth over the area of your neck where the thyroid gland is located. The probe detects the location and intensity of the rays given off by the radioactive material. A computer displays how much of the tracer is taken up by the thyroid gland.The test takes less than 30 minutes, but you will need to come back twice to have the scans performed. How to Prepare for the Test Follow instructions about not eating before the test. You may be told not to eat after midnight the night before your test.Your health care provider will tell you if you need to stop taking medicines before the test that may affect your test results. Do not stop taking any medicine without first talking to your provider.Tell your provider if you have:Diarrhea (may decrease absorption of the radioactive iodine) Had recent CT scans using intravenous or oral iodine-based contrast (within the past 2 weeks) CT scansA computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body. Related tests include:Abdomin...ImageRead Article Now Book Mark Article Too little or too much iodine in your diet How the Test will Feel There is no discomfort. You can eat beginning about 1 to 2 hours after swallowing the radioactive iodine. You can go back to a normal diet after the test. Why the Test is Performed This test is done to check thyroid function. It is often done when blood tests of thyroid function show that you may have an overactive thyroid gland.Overactive thyroid glandHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Normal Results These are normal results at 6 and 24 hours after swallowing the radioactive iodine:At 6 hours: 5% to 15% At 24 hours: 10% to 30% Some testing centers measure only at 24 hours. Values may vary depending on the amount of iodine in your diet. Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your specific test results. What Abnormal Results Mean Higher-than-normal uptake may be due to an overactive thyroid gland. The most common cause is Graves disease.Graves diseaseGraves disease is an autoimmune disorder that leads to an overactive thyroid gland (hyperthyroidism). An autoimmune disorder is a condition that occ...ImageRead Article Now Book Mark Article Other conditions can cause some areas of higher-than-normal uptake in the thyroid gland. These include:An enlarged thyroid gland that contains nodules producing too much thyroid hormone (toxic nodular goiter) Toxic nodular goiterToxic nodular goiter involves an enlarged thyroid gland. The gland contains areas that have increased in size and formed nodules. One or more of th...ImageRead Article Now Book Mark Article A single thyroid nodule that is producing too much thyroid hormone (toxic adenoma) These conditions often result in normal uptake, but the uptake is concentrated into a few (hot) areas while the rest of the thyroid gland does not take up any iodine (cold areas). This can only be determined if the scan is done along with the uptake test.Lower-than-normal uptake may be due to:Factitious hyperthyroidism (taking too much thyroid hormone medicine or supplements) Factitious hyperthyroidismFactitious hyperthyroidism is higher-than-normal thyroid hormone levels in the blood and symptoms that suggest hyperthyroidism. It occurs from takin...ImageRead Article Now Book Mark Article Iodine overload Subacute thyroiditis (swelling or inflammation of the thyroid gland) Subacute thyroiditisSubacute thyroiditis is an immune reaction of the thyroid gland that often follows an upper respiratory infection. The thyroid gland is located in th...ImageRead Article Now Book Mark Article Silent (or painless) thyroiditis Silent (or painless) thyroiditisSilent thyroiditis is an immune reaction of the thyroid gland. The disorder can cause hyperthyroidism, followed by hypothyroidism. The thyroid gland...ImageRead Article Now Book Mark Article Amiodarone (medicine to treat some kinds of heart disease that may also have effects on the thyroid gland) Risks All radiation has possible side effects. The amount of radiation in this test is very small, and there have been no documented side effects.Women who are pregnant or breastfeeding should not have this test. Talk to your provider if you have concerns about this test. Considerations The radioactive iodine leaves your body through your urine. You need not take special precautions, such as flushing twice after urinating, for 24 to 48 hours after the test because the dose of radioactive iodine is very low. Ask your provider or the radiology/nuclear medicine team performing the scan about taking precautions.Open ReferencesReferencesFaix JD. Thyroid function testing (thyrotropin, triiodothyronine, and thyroxine). In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 68.Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Mettler FA, Guiberteau MJ. Thyroid, parathyroid, and salivary glands. In: Mettler FA, Guiberteau MJ, eds. Essentials of Nuclear Medicine and Molecular Imaging. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 4.Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.AllVideoImagesTogThyroid uptake test - illustration Radioactive iodine uptake test is a type of nuclear test performed to evaluate thyroid function. The patient ingests radioactive iodine (I-123 or I-131) capsules or liquid. After a time (usually 4 and 24-hours later), a gamma probe is placed over the thyroid gland to measure the amount of radioiodine uptake in the thyroid gland. The values are then compared.Thyroid uptake testillustrationThyroid uptake test - illustration Radioactive iodine uptake test is a type of nuclear test performed to evaluate thyroid function. The patient ingests radioactive iodine (I-123 or I-131) capsules or liquid. After a time (usually 4 and 24-hours later), a gamma probe is placed over the thyroid gland to measure the amount of radioiodine uptake in the thyroid gland. The values are then compared.Thyroid uptake testillustration Tests for Radioactive iodine uptake Radioactive iodine uptakeThyroid scanRelated Information Thyroid scan(Medical Test)T3 test(Medical Test)Free T4 test(Medical Test)Hyperthyroidism(Condition)Chronic thyroiditis (Hashimoto disease)(Condition)Simple goiter(Condition)Hypothyroidism(Condition)Subacute thyroiditis(Condition)Graves disease(Condition)Silent thyroiditis(Condition)Hypothyroidism - InDepth(In-Depth) Review Date: 2/28/2024 Reviewed By: Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. 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Radioactive iodine uptakeThyroid uptake; Iodine uptake test; RAIURadioactive iodine uptake (RAIU) tests thyroid function. It measures how much radioactive iodine is taken up by your thyroid gland in a certain time period.A similar test is the thyroid scan. The 2 tests are commonly performed together, but they can be done separately.Thyroid scanA thyroid scan uses a radioactive iodine tracer to examine the structure and function of the thyroid gland. This test is often done together with a ...ImageRead Article Now Book Mark Article How the Test is Performed The test is done in this way:You are given a pill that contains a tiny amount of radioactive iodine. After swallowing it, you wait as the iodine collects in the thyroid. The first uptake is usually done 4 to 6 hours after you take the iodine pill. Another uptake is usually done 24 hours later. During the uptake, you lie on your back on a table. A device called a gamma probe is moved back and forth over the area of your neck where the thyroid gland is located. The probe detects the location and intensity of the rays given off by the radioactive material. A computer displays how much of the tracer is taken up by the thyroid gland.The test takes less than 30 minutes, but you will need to come back twice to have the scans performed. How to Prepare for the Test Follow instructions about not eating before the test. You may be told not to eat after midnight the night before your test.Your health care provider will tell you if you need to stop taking medicines before the test that may affect your test results. Do not stop taking any medicine without first talking to your provider.Tell your provider if you have:Diarrhea (may decrease absorption of the radioactive iodine) Had recent CT scans using intravenous or oral iodine-based contrast (within the past 2 weeks) CT scansA computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body. Related tests include:Abdomin...ImageRead Article Now Book Mark Article Too little or too much iodine in your diet How the Test will Feel There is no discomfort. You can eat beginning about 1 to 2 hours after swallowing the radioactive iodine. You can go back to a normal diet after the test. Why the Test is Performed This test is done to check thyroid function. It is often done when blood tests of thyroid function show that you may have an overactive thyroid gland.Overactive thyroid glandHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Normal Results These are normal results at 6 and 24 hours after swallowing the radioactive iodine:At 6 hours: 5% to 15% At 24 hours: 10% to 30% Some testing centers measure only at 24 hours. Values may vary depending on the amount of iodine in your diet. Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your specific test results. What Abnormal Results Mean Higher-than-normal uptake may be due to an overactive thyroid gland. The most common cause is Graves disease.Graves diseaseGraves disease is an autoimmune disorder that leads to an overactive thyroid gland (hyperthyroidism). An autoimmune disorder is a condition that occ...ImageRead Article Now Book Mark Article Other conditions can cause some areas of higher-than-normal uptake in the thyroid gland. These include:An enlarged thyroid gland that contains nodules producing too much thyroid hormone (toxic nodular goiter) Toxic nodular goiterToxic nodular goiter involves an enlarged thyroid gland. The gland contains areas that have increased in size and formed nodules. One or more of th...ImageRead Article Now Book Mark Article A single thyroid nodule that is producing too much thyroid hormone (toxic adenoma) These conditions often result in normal uptake, but the uptake is concentrated into a few (hot) areas while the rest of the thyroid gland does not take up any iodine (cold areas). This can only be determined if the scan is done along with the uptake test.Lower-than-normal uptake may be due to:Factitious hyperthyroidism (taking too much thyroid hormone medicine or supplements) Factitious hyperthyroidismFactitious hyperthyroidism is higher-than-normal thyroid hormone levels in the blood and symptoms that suggest hyperthyroidism. It occurs from takin...ImageRead Article Now Book Mark Article Iodine overload Subacute thyroiditis (swelling or inflammation of the thyroid gland) Subacute thyroiditisSubacute thyroiditis is an immune reaction of the thyroid gland that often follows an upper respiratory infection. The thyroid gland is located in th...ImageRead Article Now Book Mark Article Silent (or painless) thyroiditis Silent (or painless) thyroiditisSilent thyroiditis is an immune reaction of the thyroid gland. The disorder can cause hyperthyroidism, followed by hypothyroidism. The thyroid gland...ImageRead Article Now Book Mark Article Amiodarone (medicine to treat some kinds of heart disease that may also have effects on the thyroid gland) Risks All radiation has possible side effects. The amount of radiation in this test is very small, and there have been no documented side effects.Women who are pregnant or breastfeeding should not have this test. Talk to your provider if you have concerns about this test. Considerations The radioactive iodine leaves your body through your urine. You need not take special precautions, such as flushing twice after urinating, for 24 to 48 hours after the test because the dose of radioactive iodine is very low. Ask your provider or the radiology/nuclear medicine team performing the scan about taking precautions.Open ReferencesReferencesFaix JD. Thyroid function testing (thyrotropin, triiodothyronine, and thyroxine). In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 68.Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Mettler FA, Guiberteau MJ. Thyroid, parathyroid, and salivary glands. In: Mettler FA, Guiberteau MJ, eds. Essentials of Nuclear Medicine and Molecular Imaging. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 4.Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.