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Sodium iodide-i-131 Side Effects

For the Consumer

Applies to sodium iodide-i-131: oral capsule, oral kit, oral solution

As well as its needed effects, sodium iodide-i-131 may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking sodium iodide-i-131, check with your doctor or nurse immediately:

After treatment of overactive thyroidSymptoms of an underactive thyroid
  • Changes in menstrual periods
  • clumsiness
  • coldness
  • drowsiness
  • dry, puffy skin
  • headache
  • listlessness
  • muscle aches
  • thinning of the hair (temporary)
  • unusual tiredness or weakness
  • weight gain
RareAfter treatment of overactive thyroid
  • Excessive sweating
  • fast, irregular, pounding, or racing heartbeat or pulse
  • fever
  • unusual irritability
After treatment of cancer of the thyroid
  • Black, tarry stools
  • blood in the urine or stools
  • cough or hoarseness
  • fever or chills
  • lower back or side pain
  • painful or difficult swallowing
  • painful or difficult urination
  • pinpoint red spots on the skin
  • unusual bleeding or bruising
Incidence not known:After treatment of overactive thyroid
  • Chest pain
  • fast, pounding, or irregular heartbeat or pulse
  • hives, itching, and rash
  • nervousness
  • sensitivity to heat
  • sweating
  • tenderness of salivary glands
  • trouble sleeping
  • weight loss
After treatment of cancer of the thyroid
  • Abdominal or stomach cramps
  • bleeding gums
  • bone pain
  • diarrhea
  • feeling of discomfort
  • loss of appetite
  • nausea
  • sore throat
  • unusual tiredness or weakness
  • vomiting
  • weakness

Minor Side Effects

Some sodium iodide-i-131 side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:After treatment of overactive thyroid or cancer of the thyroid
  • Neck tenderness or swelling
  • sore throat
After treatment of cancer of the thyroid
  • Loss of taste (temporary)
  • nausea and vomiting (temporary)
  • tenderness of the salivary glands

For Healthcare Professionals

Applies to sodium iodide-i-131: compounding powder, oral capsule, oral liquid


Cardiovascular side effects have included chest pain and tachycardia.[Ref]


Dermatologic side effects have included itching skin, rash, and hives.[Ref]


Endocrine side effects have included acute thyroid crisis.[Ref]


Gastrointestinal side effects have included nausea and vomiting.[Ref]


Hematologic side effects have included blood dyscrasia, leukopenia, thrombocytopenia, depression of hematopoietic system, and anemia.[Ref]


Local side effects have included tenderness and swelling of the neck, pain on swallowing, sore throat, and cough (usually around the third day after treatment).[Ref]


Oncologic side effects have included acute leukemia.[Ref]


Other side effects have included temporary thinning of the hair (may occur 2 to 3 months after treatment), chromosomal abnormalities, radiation sickness, and death.[Ref]


1. Saha GB. "Fundamentals of Nuclear Pharmacy. 4th ed." New York, NY: Springer-Verlag (1998):

2. "Product Information. Sodium Iodide-1-131 (sodium iodide-I-131)." Mallinckrodt Medical Inc, St. Louis, MO.

It is possible that some side effects of sodium iodide-i-131 may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.