Side Effects of Iodine-131 Treatment: What Patients Should Know

Radioactive iodine therapy, commonly known as Iodine-131 (I-131) treatment, is widely used in managing thyroid disorders such as hyperthyroidism and thyroid cancer. Compared to traditional chemotherapy or external beam radiation, I-131 is generally associated with milder side effects. Most patients tolerate the treatment well and experience few or no significant adverse reactions. However, a subset of individuals may encounter temporary discomforts that typically resolve on their own over time.

Common Short-Term Side Effects

Shortly after ingesting the radioactive iodine capsule or liquid, some patients report feeling unusually fatigued or notice mild swelling in the neck area. This localized inflammation is usually transient and tends to appear within the first week post-treatment. The sensation may include a feeling of tightness or pressure around the thyroid gland, but it rarely requires medical intervention and diminishes as the body clears the radiation.

Gastrointestinal Reactions

Nausea and occasional vomiting are among the more frequently reported side effects following I-131 administration. These symptoms are typically mild and short-lived, often occurring within the first 24 to 48 hours after treatment. Staying hydrated, eating light meals, and taking prescribed anti-nausea medication—if recommended by a physician—can help manage these gastrointestinal disturbances effectively.

Salivary Gland and Oral Discomfort

A smaller percentage of patients may experience dry mouth, excessive tearing, or altered taste sensations. These occur because salivary glands can absorb small amounts of radioactive iodine, leading to temporary dysfunction. Some individuals also report swelling of the parotid glands (located near the jaw), which can cause discomfort while chewing or speaking. These issues usually develop within hours to several months after treatment and often improve with time. Chewing sugar-free gum or sucking on citrus candies may stimulate saliva flow and reduce symptoms.

Blood Count Changes

In rare cases, patients might observe a temporary decrease in white blood cell or platelet counts within one to two months after therapy. This hematological shift is generally mild and self-limiting, meaning the body naturally restores normal levels without requiring specific treatment. Routine blood tests are usually recommended during follow-up visits to monitor these parameters and ensure recovery.

Impact on Female Reproductive Health

Women undergoing I-131 therapy may experience menstrual irregularities, including delayed periods or temporary amenorrhea (absence of menstruation). These changes are typically reversible and resolve spontaneously within a few weeks to several months. Hormonal balance usually returns to baseline as the body adjusts post-treatment. Patients who are concerned about fertility or long-term reproductive health are advised to discuss family planning with their healthcare provider before starting therapy.

Minimizing Risks and Ensuring Safety

To reduce the intensity of side effects, doctors often recommend increased fluid intake to help flush excess radiation from the body. Patients may also be instructed to practice safe radiation hygiene—such as maintaining distance from others, especially children and pregnant women—for a few days after treatment. Adhering to medical guidance significantly lowers both personal risk and potential exposure to household members.

Overall, while Iodine-131 therapy does carry some potential side effects, they are generally manageable and temporary. With proper preparation and post-treatment care, most individuals recover smoothly and benefit greatly from this targeted and effective form of nuclear medicine.