Health Guide

Sodium iodide I 123 (By mouth)

Sodium Iodide I 123 (SOE-dee-um EYE-oh-dide I 123)

Used as part of a medical test of the thyroid.

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You may not be able to receive this medicine if you have had an allergic reaction to iodine-containing radiopharmaceuticals.

How to Use This Medicine:


  • Carefully follow your doctor's instructions about any special diet. You might need to avoid foods and medicines that contain iodine before you have your test.
  • A nurse or other trained health professional will give you this medicine.
  • Your thyroid test will be given six hours after you receive your dose of this medicine.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are using a thyroid medicine such as levothyroxine, methimazole, Cytomel®, Synthroid®, or Tapazole®.

Warnings While Using This Medicine:

  • Make sure your doctor knows if you are pregnant or breastfeeding. Tell your doctor if you have kidney disease, or if you have any allergies to foods or dyes.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Chest pain, fast or pounding heartbeat.

If you notice these less serious side effects, talk with your doctor:

  • Nausea or vomiting.
  • Rash.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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