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Endocrinology · UK

Radioactive iodine - definitive treatment for an overactive thyroid, and for thyroid cancer.

A single oral capsule of iodine-131 that concentrates in thyroid tissue and shuts it down - for Graves’ disease, toxic nodules and ablation after thyroidectomy for differentiated thyroid cancer. Consultant endocrinologist and nuclear medicine physician together, the hypothyroidism and isolation conversation up front, and an MDT for every cancer case.

See indicative pricing
A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Indicative pricing

What private radioactive iodine treatment costs in the UK.

Indicative ranges across our partner nuclear medicine units.

In short

£2,000–£3,500, home the same day.

Treatment Indicative range
Endocrinology or nuclear medicine consultation £250–£450
Low-dose I-131 for hyperthyroidism (200–400 MBq) £2,000–£3,500
High-dose I-131 for hyperthyroidism (400–800 MBq) £3,000–£4,500
I-131 ablation after thyroidectomy (1,100–3,700 MBq) £4,500–£8,000
rhTSH (Thyrogen) stimulation × 2 doses £1,500–£2,200
Post-therapy whole-body scan £450–£800
Thyroglobulin and follow-up bloods £120–£220

Prices vary by centre, by the activity (MBq) prescribed, by whether inpatient isolation is required and by whether rhTSH (Thyrogen) stimulation is included instead of hormone withdrawal. Cancer ablation packages are always at the top of the range because of the inpatient nights and post-therapy scan.

The problem

The right dose, the isolation plan, and the hypothyroidism follow-up you deserve.

Radioactive iodine is where general endocrinology quietly under-delivers - isolation planning left vague, hypothyroidism dismissed as a side effect and fertility timing not raised. We fix all three before you swallow the capsule.

  • Isolation planned around your life

    Who is at home, are there children or a pregnant partner, do you live alone - all of this drives whether you go home the same day or stay inpatient, and where you sleep for the next week.

  • Hypothyroidism is expected, not a side effect

    Levothyroxine is planned from day one - the prescription, the follow-up bloods, the dose titration. Not a surprise phone call six weeks later.

  • Fertility and pregnancy timing

    Six months of contraception for both women and men after treatment. If a pregnancy is planned within a year, we say so before the dose is given.

When it helps

When radioactive iodine is the right step.

The situations we see most, plus the one red flag that means a different treatment route rather than a routine I-131 booking.

  • Graves’ disease

    Autoimmune hyperthyroidism where antithyroid drugs have failed, relapsed or are not tolerated - I-131 is a definitive cure.

  • Toxic multinodular goitre

    An enlarged nodular thyroid producing too much hormone - I-131 shrinks the gland and controls the overactivity.

  • Toxic (autonomous) adenoma

    A single hot nodule driving hyperthyroidism - targeted I-131 concentrates in the nodule and spares the rest of the gland.

  • Differentiated thyroid cancer ablation

    Post-thyroidectomy ablation of residual normal thyroid tissue in papillary and follicular carcinoma, to enable surveillance and lower recurrence.

  • Recurrent or metastatic thyroid cancer

    Iodine-avid recurrence in the neck or distant metastases - higher-dose I-131 as therapeutic treatment.

  • Relapse after antithyroid drugs

    Hyperthyroidism that has come back after a full course of carbimazole or propylthiouracil - I-131 avoids years of medication and monitoring.

  • Not suitable for surgery

    Where thyroidectomy carries too much risk - cardiac disease, previous neck surgery, obesity or patient preference - I-131 is the definitive alternative.

  • Red flag: thyroid eye disease

    Active moderate-to-severe Graves’ orbitopathy is a relative contraindication - I-131 can worsen it. Steroid cover or a different route (drugs, surgery) must be discussed first.

Dose options

Activity and preparation depend on the indication.

What each option involves - activity in MBq or mCi, low-iodine diet, TSH stimulation (withdrawal or rhTSH), and whether isolation is at home or inpatient.

  • Low-dose I-131 for hyperthyroidism

    Typically 200–400 MBq as a single oral capsule for Graves’ disease and toxic nodules. Same-day home isolation for 3–7 days.

  • High-dose I-131 for hyperthyroidism

    Up to 800 MBq for larger goitres or previous treatment failure. Same-day or single overnight stay depending on the local licence.

  • Ablation dose after thyroidectomy

    1,100–3,700 MBq (30–100 mCi) to ablate the thyroid remnant in differentiated thyroid cancer. Inpatient in a lead-shielded room for 1–3 nights.

  • Therapeutic dose for metastatic disease

    Higher activities, sometimes dosimetry-guided, for iodine-avid recurrence or distant metastases. Always inpatient and MDT-planned.

  • Thyroid hormone withdrawal preparation

    Levothyroxine stopped for 3–4 weeks (or T3 for 2 weeks) before ablation to raise TSH above 30 mU/L. Effective, but you feel hypothyroid.

  • rhTSH (Thyrogen) stimulation

    Two intramuscular injections on consecutive days as an alternative to hormone withdrawal. You stay on levothyroxine and feel well throughout.

  • Low-iodine diet

    For one to two weeks before the dose - no seafood, iodised salt, dairy in excess, seaweed or iodine-containing supplements. Improves iodine uptake by the target tissue.

  • Diagnostic vs therapeutic scan

    A small diagnostic dose (74–185 MBq) for scanning, versus the therapeutic dose above. We make clear which you are having and why.

Safety and follow-up

What to expect afterwards - honestly.

Radioactive iodine is a well-established treatment. The things worth planning are isolation, the transition to levothyroxine, and - for anyone considering a family - the six-month pregnancy deferral.

  • The dose is a single oral capsule

    You swallow a capsule with water in the iodine suite - no anaesthetic, no injection, no procedure. Ten minutes in the room, then home or to your shielded room.

  • Isolation and distance rules

    Three to seven days at home for hyperthyroidism, one to three nights inpatient for cancer ablation. Distance from children and pregnant women, own bathroom, own bedding, careful handwashing.

  • Pregnancy is an absolute contraindication

    Pregnancy and breastfeeding are absolute bars. Pregnancy must be avoided for six months after treatment (both women and men), and breastfeeding stopped before the dose.

  • Hypothyroidism is expected, not a complication

    Near-universal after cancer ablation and about 80 percent at one year after hyperthyroidism treatment. Lifelong levothyroxine, easy tablets, monitored every 6–8 weeks until stable, then annually.

  • Salivary glands, tear ducts, taste

    Sialadenitis (sore, swollen parotid glands), dry mouth, altered taste and dry eyes are the commonest short-term issues. Sucking citrus sweets and hydration in the first 24 hours reduce the risk.

  • Thyroid eye disease can flare

    Active moderate-to-severe Graves’ orbitopathy can worsen after I-131. Where it is present we consider steroid cover, or choose antithyroid drugs or surgery instead.

  • Fertility and future pregnancy

    Fertility is preserved. Conception should be deferred for six months after treatment (men and women), long enough for residual radiation and any transient effect on gametes to settle.

  • Secondary cancer risk is very small

    A small excess long-term risk of leukaemia and other cancers has been reported at high cumulative doses. For standard single doses the risk is very low and outweighed by the benefit of definitive treatment.

  • Red flags after the dose

    Severe neck swelling, breathing difficulty, chest pain, rapidly worsening eye symptoms, or signs of severe hypothyroidism (marked fatigue, cold intolerance, weight gain) need the same-day team, not a routine call.

Reading your treatment note

Your treatment note in four parts. Read the last one first.

Whether the dose was for hyperthyroidism or cancer ablation, the letter the nuclear medicine team sends you keeps to the same shape.

A UK consultant endocrinologist reviewing a patient’s radioactive iodine treatment notes

A quiet reminder

Nuclear medicine language is precise and can read coldly - we translate it for you.

If you would like us to talk you through the treatment note and the post-therapy scan before your review, just ask.

  1. 01 Header

    Indication, activity and route

    Why the treatment was given (Graves’, toxic nodule, cancer ablation, metastatic), how much I-131 was administered in MBq or mCi, and whether by capsule or liquid.

  2. 02 Preparation

    TSH stimulation and iodine status

    Whether the dose followed thyroid hormone withdrawal or rhTSH (Thyrogen). The TSH level at treatment, the low-iodine diet period, and any recent iodinated contrast.

  3. 03 Findings

    Post-therapy scan and uptake

    The whole-body scan performed 3–7 days after the dose. Where iodine is taken up - thyroid bed remnant, neck nodes, lung or bone metastases - and whether the pattern matches expectations.

  4. 04 Impression

    Follow-up, levothyroxine, surveillance

    Read this first: when to start or restart levothyroxine, the follow-up interval for thyroid function and thyroglobulin, and the next scan or MDT plan.

Recognised by major UK insurers

BupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealix

Radioactive iodine is usually covered when medically indicated for hyperthyroidism or thyroid cancer. Cancer ablation packages are commonly covered under oncology pathways.

Frequently asked

Everything we get asked about radioactive iodine.

Quick answers on isolation, hypothyroidism, fertility, thyroid eye disease, cost and follow-up.

  • Will radioactive iodine make me radioactive to other people?

    For a short time, yes. You emit a small amount of radiation for a few days. That is why isolation rules exist - distance from children and pregnant women, own bathroom, own bedding, careful handwashing. For low-dose hyperthyroidism cases it is 3–7 days at home; for high-dose cancer ablation it is 1–3 nights in a lead-shielded room until levels fall below the discharge threshold.

  • Will I become hypothyroid after treatment?

    Almost certainly. It is near-universal after cancer ablation - the intent is to destroy any remaining thyroid tissue. After treatment for hyperthyroidism, roughly 80 percent of patients are hypothyroid within a year and most eventually. Hypothyroidism is easy to manage with a daily levothyroxine tablet and 6–8-weekly bloods until the dose is stable.

  • How long do I have to avoid pregnancy after radioactive iodine?

    Six months, for both women and men. Pregnancy during or shortly after treatment must be avoided because of the radiation risk to a foetus and to gametes. Breastfeeding must stop before the dose and cannot be resumed for this baby. If pregnancy is planned, we time treatment carefully around it.

  • What is the low-iodine diet and why does it matter?

    For one to two weeks before the dose you avoid iodine-rich foods - seafood, seaweed, iodised salt, excess dairy, egg yolks in excess, iodine-containing supplements and multivitamins. Lowering body iodine stores means the target tissue (thyroid remnant, cancer cells or overactive gland) takes up more of the radioactive iodine and treatment works better.

  • Is radioactive iodine better than surgery or antithyroid drugs?

    It depends. For Graves’ disease relapsed after drugs, and for toxic nodules, I-131 is a good definitive option - no operation, no scar, high success. For very large goitres, compressive symptoms, suspicion of malignancy, active thyroid eye disease or a wish to conceive within six months, thyroidectomy or continued drugs may be better. It is a shared decision.

  • How much does private radioactive iodine cost in the UK?

    Roughly £2,000–£3,500 for a low-dose hyperthyroidism treatment, £3,000–£4,500 for a higher-dose hyperthyroidism treatment, and £4,500–£8,000 for ablation after thyroidectomy - the higher end where inpatient nights and rhTSH (Thyrogen) stimulation are included.

  • Can I have I-131 if I have thyroid eye disease?

    With caution. Active moderate-to-severe Graves’ orbitopathy can flare after I-131. Where eye disease is present we usually offer steroid cover during and after treatment, or choose antithyroid drugs or thyroidectomy instead. Ophthalmology input is standard before we proceed.

  • Will the treatment affect my taste, saliva or eyes?

    Often, mildly and briefly. Sialadenitis - sore, swollen parotid glands - and a metallic taste, dry mouth or dry eyes are the commonest short-term issues, usually within 24–72 hours. Sucking citrus sweets, chewing gum and drinking plenty of water for the first day reduce the risk. Longer-term dry mouth or dry eyes are uncommon at standard doses.

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