Radioactive Iodine Therapy: What It Is, How It Works, and What to Expect

When your thyroid goes off track—whether it’s overactive, enlarged, or cancerous—radioactive iodine therapy, a targeted treatment that uses a radioactive form of iodine to destroy thyroid tissue. Also known as iodine-131 therapy, it’s one of the most precise ways to treat thyroid conditions without surgery. Unlike external radiation, it doesn’t zap your whole body. Instead, your thyroid naturally pulls in iodine, so the radiation goes exactly where it’s needed.

This treatment isn’t for everyone. It’s most often used for hyperthyroidism, a condition where the thyroid makes too much hormone, especially when meds or surgery aren’t the best fit. It’s also a standard step after thyroid removal in thyroid cancer, a treatment that wipes out leftover thyroid cells to prevent recurrence. The goal? Stop the gland from overproducing hormones or eliminate cancer cells that might hide after surgery.

What happens during treatment? You swallow a capsule or liquid containing iodine-131. It enters your bloodstream, gets absorbed by thyroid cells, and delivers radiation right to them. Healthy cells nearby barely notice. Most people go home the same day, but you’ll need to avoid close contact with others for a few days—especially kids and pregnant people—because your body temporarily emits low levels of radiation. Side effects are usually mild: dry mouth, sore throat, or a temporary change in taste. Some people feel tired for a week or two. Long-term, your thyroid may stop working entirely, which means you’ll need daily thyroid hormone pills—but that’s often the point.

Not all thyroid issues need this. If you’re young, pregnant, or have mild overactivity, doctors might try other options first. But for many, radioactive iodine therapy is the most effective, least invasive solution. It’s been used safely for over 70 years, with millions of patients treated worldwide.

Below, you’ll find real patient-focused articles that dig into what this treatment really means—how it interacts with other meds, what side effects to watch for, how to prepare, and what to expect after. Whether you’re considering it, just had it, or are helping someone who did, these posts give you the facts without the fluff.