How do I get ready for radioactive iodine treatment for Graves’ disease?

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: June 19, 2025Updated: June 19, 2025

Summary

To prepare for radioactive iodine (RAI) therapy for Graves’ disease, stop antithyroid drugs 5–7 days beforehand, follow a strict low-iodine diet for 10–14 days, check a recent pregnancy test if relevant, and confirm that your thyroid-stimulating hormone (TSH) receptor antibodies are elevated so ablation is justified. Arrange for 3-7 days of post-treatment radiation precautions at home and discuss temporary beta-blockers to control symptoms while waiting for RAI to work.

What are the key steps I must complete before my RAI dose?

Most patients need to change medicines, diet and scheduling details in the weeks before RAI. These steps make the radioactive iodine concentrate in the overactive thyroid so treatment is effective.

  • Stop methimazole or propylthiouracil 5–7 days before RAIContinuing antithyroid drugs lowers iodine uptake by as much as 40 %, reducing cure rates.
  • Stay on beta-blockers until the morning of treatmentDrugs like atenolol do not interfere with iodine uptake and keep heart rate under 90 bpm.
  • Schedule a thyroid uptake scan if not done in the past 6 weeksA 24-hour uptake above 30 % confirms Graves’ physiology and predicts good response.
  • Arrange contraception or pregnancy testingWomen of child-bearing potential must show a negative test within 72 hours of dosing by national radiation safety law.
  • Plan 3–7 days of home isolationMost adults excrete 80 % of the dose in 48 hours, but having a separate bathroom speeds clearance.
  • Follow a low-iodine diet for the seven days before dosingDepleting dietary iodine (avoid seafood, seaweed and keep dairy to a minimum) for the week leading up to treatment makes the thyroid more avid for the radioactive dose, improving uptake. (NHS)
  • Delay RAI for at least 2–3 months after any CT scan with iodinated contrastResidual contrast iodine can saturate thyroid stores; many centers require an 8–12 week wait or a 24-hour urine iodine < 100 µg before proceeding to ensure effective therapy. (HTES)

References

Which warning signs mean I should call my doctor before RAI day?

RAI is safe when the thyroid is not dangerously hyperactive and when no pregnancy exists. Certain symptoms signal the need for urgent reassessment.

  • Resting heart rate above 120 bpmSevere tachycardia raises the risk of thyroid storm during or after RAI.
  • Uncontrolled atrial fibrillationA-fib increases stroke risk; INR and rate control must be optimized first.
  • Eye pain or sudden double visionRapidly worsening Graves’ ophthalmopathy may require steroids before RAI.
  • Positive pregnancy testRAI is contraindicated at any stage of pregnancy because it can ablate the fetal thyroid.
  • High free T4 despite maximum medicationLevels more than triple the upper limit of normal predict post-RAI thyroid storm.
  • Recent iodinated contrast can delay or cancel treatmentA CT scan with iodinated contrast in the last 2–3 months can saturate your thyroid with non-radioactive iodine; your doctor may postpone RAI or check a 24-hour urine iodine level (<100 µg) before going ahead. (HTES)

References

Are there common, less serious issues that can delay my treatment?

Most postponements are due to ordinary problems rather than emergencies. Knowing them helps you avoid last-minute rescheduling.

  • Accidental iodine exposure from contrast scansCT with iodinated contrast can saturate the gland for 6–8 weeks.
  • Dietary slip-ups with seaweed or sushiA single nori roll can supply over 500 µg of iodine, enough to lower uptake.
  • Recent amiodarone startAmiodarone contains 75 mg of iodine per tablet; stop at least 3 months before RAI if possible.
  • Multivitamin with iodineCheck labels—most standard multivitamins add 150 µg iodine, equal to a full day’s allowance.
  • Breast-feeding not yet discontinuedRadioiodine passes into milk; pumping and discarding for 6 weeks is required before scheduling.
  • Antithyroid tablets not stopped in timeMethimazole, carbimazole or PTU competitively block iodine trapping; the ESHT preparation guide tells patients to discontinue them 7 days before dosing or the appointment will need to be moved. (ESHT)
  • Pregnancy test pending or positiveBecause radio-iodine is contraindicated in pregnancy, Gateshead NHS mandates a pregnancy test for women under 55 and will cancel treatment if the result is positive or unclear. (Gateshead NHS)

References

What can I do at home to make RAI safer and more comfortable?

Small adjustments before and after the dose speed recovery and protect family members.

  • Follow a 2-week low-iodine dietLimit dairy, seafood, iodized salt and bakery bread to keep daily iodine under 50 µg.
  • Hydrate with 2–3 liters of fluid dailyRapid renal clearance reduces total-body radiation by up to 15 %.
  • Stock disposable utensils and separate laundry binsRadioactivity on saliva and sweat is low but detectable for 2–3 days.
  • Use sour candies every 2–3 hours post-doseStimulating salivation cuts thyroid-adjacent salivary gland radiation exposure in half.
  • Arrange child-care or pet-careMaintain at least 6 feet distance from children under 12 and pregnant women for 3 days.
  • Sleep in a separate bed to cut partner exposureUniversity of Michigan instructions recommend sleeping in a different bed from other adults for 3–15 days and from pregnant partners or young children for 15–27 days, because nighttime proximity delivers a large share of a partner’s radiation dose. (UMich)
  • Double-flush and wipe bathroom surfaces for one weekKaiser Permanente advises patients to sit while using the toilet, wipe any splashes, and flush twice after each use during the first 7 days to keep residual I-131 in urine from exposing family members. (Kaiser)

References

Which blood tests and medicines matter most around RAI?

Lab values guide timing and dosing, while a few medications improve safety without reducing efficacy.

  • Free T4 and total T3 within 48 hoursAim for levels less than twice the upper limit to reduce post-RAI hormone surge.
  • TSH receptor antibody (TRAb) levelHigh TRAb predicts faster response; levels above 15 IU/L justify higher RAI activity.
  • Complete blood count and liver panel if previously abnormalRule out agranulocytosis from antithyroid drugs before stopping them.
  • Prednisone taper for eye diseaseA brief course starting 1 day before RAI lowers worsening orbitopathy odds from 40 % to 16 %.
  • Potassium iodide 7 days after RAIA short post-treatment block traps residual radiation in the thyroid and spares the rest of the body.
  • Pause antithyroid drugs several days pre-RAIPrior methimazole or PTU exposure doubled the single-dose treatment failure rate (21 % vs 9 %), so most centers stop these agents 3–7 days before administering I-131. (AACE)
  • Push oral fluids in first 48 hUW guidelines urge generous water intake and frequent voiding during the first 48 hours after dosing to speed radioiodine clearance and lower whole-body exposure. (UW)

References

How can Eureka’s AI doctor make RAI preparation easier?

The Eureka app maps out timelines, reminds you to stop medications and alerts you if new symptoms should prompt labs.

  • Personalized countdown checklistThe app syncs with your prescription dates and flags the exact day to stop methimazole.
  • Automated vitals trackingA daily heart-rate log warns you if resting pulse drifts above 100 bpm.
  • Smart symptom triageIf you enter eye pain, Eureka prompts an urgent message to your endocrinologist.

Why do Graves’ patients rate Eureka so highly for RAI follow-up?

After treatment, hormone levels swing for months. Continuous support matters.

  • 4.8 / 5 satisfaction among post-RAI usersPatients praise fast lab result explanations and dose-adjustment advice.
  • Safe prescription reviewEureka’s doctors approve or modify beta-blocker refills within 24 hours.
  • Private record storageAll notes and labs stay encrypted; you control who sees them.
  • Integrated lab orderingThe AI suggests a TSH at 6 weeks; your physician can tap once to send the order.

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Frequently Asked Questions

Do I really need to stop methimazole before RAI if my levels are high?

Yes. Even if free T4 is elevated, continuing methimazole sharply lowers iodine uptake and can cause treatment failure.

Can I drink coffee on the low-iodine diet?

Plain black coffee is fine; avoid dairy creamers and soy milk that add iodine.

How long should I wait to get pregnant after RAI?

Most endocrinologists recommend at least 6 months so your thyroid levels stabilize and radiation clears.

Will I feel better right after the dose?

No. The thyroid often stays overactive for 4-6 weeks; beta-blockers manage symptoms during that period.

What happens if I forget about iodine in my multivitamin?

Call your clinic; a single small exposure rarely cancels treatment, but large doses may delay it 4–6 weeks.

Is it safe to fly after RAI?

Most airports flag residual radiation for up to a week. Carry a treatment letter if you must travel.

How soon will I become hypothyroid?

About 60 % develop low thyroid within 3 months; TSH should be checked at 6 weeks, 12 weeks, and then quarterly.

This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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