# Radioactive Iodine Therapy

URL: https://thethyroidologist.com/treatments/radioactive-iodine-therapy/
Section: Treatments
Last medically reviewed: 2025-11-01

> Radioactive iodine treats hyperthyroidism and thyroid cancer. How it works, who it suits, precautions, and what to expect.

Radioactive iodine (RAI) therapy uses I-131 — a radioactive form of iodine the thyroid naturally absorbs — to treat overactive thyroid tissue or thyroid cancer.
It is a well-established, targeted treatment with a long safety record.

## How it works

The thyroid uniquely absorbs iodine to make hormone. Radioactive iodine concentrates in thyroid tissue and destroys it with targeted radiation — sparing surrounding tissues almost entirely.
For hyperthyroidism, the goal is to reduce function to normal or underactive (managed with levothyroxine). For thyroid cancer, higher doses target residual cancer cells.

## Who it suits

RAI is a standard option for Graves’ disease relapse, toxic nodular goitre, and recurrent hyperthyroidism. For thyroid cancer, it is used selectively for higher-risk differentiated cancers.
It is less preferred in pregnancy, breastfeeding, and moderate-to-severe active thyroid eye disease (may worsen orbitopathy).

## Precautions and recovery

After treatment, patients may need to avoid close contact with pregnant women and young children briefly — radiation safety precautions depend on dose. Salivary glands may be mildly affected; staying hydrated helps.
Hypothyroidism is a common outcome — expected and easily managed with levothyroxine. Thyroid function is monitored regularly afterward.

## Frequently asked questions

### Is radioactive iodine safe?

Yes — it has been used for over 80 years with a strong safety record. The radiation is targeted to thyroid tissue; precautions minimize exposure to others.

### Will I become hypothyroid after RAI?

Very likely for hyperthyroidism treatment — this is expected and managed with levothyroxine. For cancer treatment, hypothyroidism is often deliberately induced first.

### Can I have RAI if I have eye disease?

RAI can potentially worsen active Graves’ orbitopathy — surgery or antithyroid drugs may be preferred when eye disease is significant.

## Disclaimer

The content on this website is for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your specific condition.

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