Medicare Coverage for Thyroid Disease: Labs, Medication, Ultrasound, Biopsy, and Thyroid Cancer

Thyroid disorders are among the most prevalent chronic conditions in adults over 65. Hypothyroidism affects roughly 10–15 percent of older women and is far more common in Medicare beneficiaries than in the general population. Hyperthyroidism, nodular thyroid disease, and differentiated thyroid cancer each require a distinct set of diagnostic and treatment services that span multiple Medicare benefit categories. This guide covers every aspect of thyroid disease management under Medicare—from the first TSH blood test to post-thyroidectomy surveillance and thyroid cancer treatment.

Thyroid Lab Tests Under Medicare Part B

TSH (Thyroid-Stimulating Hormone)

The TSH test is the cornerstone of thyroid disease diagnosis and monitoring. It is covered under Medicare Part B as a clinical diagnostic laboratory test. Clinical laboratory tests are billed under a special payment system that exempts them from the standard Part B cost-sharing rules:

• No Part B deductible applies to clinical laboratory tests
• No coinsurance — Medicare pays 100 percent of the approved amount
• The approved amount is set by the Clinical Laboratory Fee Schedule, not the physician fee schedule

Result: A TSH test ordered by your physician costs you nothing out of pocket regardless of whether you have met your $257 Part B deductible (2026) and regardless of whether you have Medigap coverage.

Free T4 (Thyroxine), Free T3, Total T4, Total T3

All standard thyroid function tests ordered as part of diagnosis or monitoring are covered as clinical laboratory tests under Part B at zero cost-sharing:

• Free T4 (free thyroxine)
• Free T3 (free triiodothyronine)
• Total T4, Total T3
• Reverse T3 (when medically indicated)

Thyroid Antibody Tests

Antibody tests used to diagnose autoimmune thyroid disease are also clinical laboratory tests covered at no cost-sharing:

• TPO antibody (anti-thyroid peroxidase): For diagnosing Hashimoto’s thyroiditis
• Thyroglobulin antibody (TgAb): For diagnosing Hashimoto’s and for post-thyroidectomy thyroid cancer surveillance
• TSI (thyroid-stimulating immunoglobulin) and TSH receptor antibody (TRAb): For diagnosing Graves’ disease

Thyroglobulin (Tg)

Thyroglobulin is the primary tumor marker for differentiated thyroid cancer (papillary and follicular) and is measured during post-thyroidectomy surveillance. It is a clinical laboratory test covered at zero cost-sharing under Part B.

Thyroid Cancer Genetic Testing

Next-generation sequencing (NGS) molecular panels (e.g., Veracyte Afirma, Thyroseq, ThyroGenX) applied to thyroid FNA specimens to characterize indeterminate nodules are covered under Part B as molecular diagnostic tests when ordered by a physician and meeting LCD (local coverage determination) criteria. Cost-sharing is typically zero (clinical laboratory billing) or minimal (physician-performed testing with CLIA complexity tiers). Verify with your insurer before ordering.

Office Visits and Endocrinology Referral

An office visit to your primary care physician or endocrinologist for thyroid disease management is covered under Part B as a physician evaluation and management (E&M) service:

• 20 percent coinsurance after the $257 Part B deductible
• Medigap Plan G covers the 20 percent coinsurance after the deductible
• Medicare Advantage: office visit copay per your plan

For established patients with stable hypothyroidism requiring only TSH monitoring and prescription refills, many visits are brief and fall into lower-cost E&M codes. For complex hyperthyroidism or thyroid nodule management, longer visits with higher E&M codes apply.

Thyroid Medications Under Medicare Part D

Levothyroxine (Generic, Brand Synthroid)

Levothyroxine is the standard medication for hypothyroidism and post-thyroidectomy thyroid hormone replacement. Generic levothyroxine is one of the least expensive medications in the United States and is covered under Medicare Part D:

• Generic levothyroxine: Typically Tier 1 (generic preferred) on virtually every Part D formulary. Copays range from $0–$15/month depending on the plan.
• Brand Synthroid: Tier 2 or Tier 3 on most formularies. Copays of $20–$60/month without Extra Help.

Because generic levothyroxine is so inexpensive, the Part D benefit has minimal impact on out-of-pocket costs for most hypothyroid patients. Even without Part D coverage, the retail price of a 90-day supply of generic levothyroxine at major pharmacy chains is $10–$30.

Liothyronine (Cytomel, generic T3)

Liothyronine is sometimes added for patients who do not achieve satisfactory symptom relief on levothyroxine monotherapy. It is a Part D covered drug at Tier 1–2. Generic liothyronine is inexpensive (typically $10–$40/month).

Hyperthyroidism Medications: Methimazole and Propylthiouracil (PTU)

Antithyroid drugs used to treat hyperthyroidism (Graves’ disease, toxic multinodular goiter) are covered under Part D:

• Methimazole (Tapazole, generic): The preferred antithyroid agent. Generic methimazole is Tier 1 on most formularies. Monthly cost: $10–$30 for typical doses.
• Propylthiouracil (PTU, generic): Reserved for first-trimester pregnancy or thyrotoxic crisis. Tier 1 generic. Monthly cost: $10–$30.

Beta-Blockers for Thyrotoxic Symptoms

Beta-blockers (propranolol, atenolol, metoprolol) used to control palpitations, tremor, and heat intolerance in hyperthyroidism are very inexpensive Tier 1 generics covered under Part D at $0–$10/month.

Thyroid Cancer Targeted Therapy (Part D)

For radioiodine-refractory differentiated thyroid cancer and medullary/anaplastic thyroid cancer, several oral targeted agents are covered under Part D:

• Lenvatinib (Lenvima): For radioiodine-refractory differentiated thyroid cancer. Retail price approximately $20,000–$25,000/month. Part D coverage with the $2,000 out-of-pocket cap (2026) means patients pay no more than $2,000/year total for Part D drugs regardless of lenvatinib’s cost.
• Sorafenib (Nexavar): Also for radioiodine-refractory DTC; Tier 5 specialty drug. Similar protection under the $2,000 cap.
• Vandetanib (Caprelsa) and cabozantinib (Cabometyx): For medullary thyroid cancer. Oral, Part D, $2,000 cap applies.
• Selpercatinib (Retevmo) and pralsetinib (Gavreto): For RET-mutant medullary and papillary thyroid cancers. Both are oral, Part D drugs with the $2,000 annual cap making previously unaffordable therapy (>$20,000/month retail) manageable.
• Dabrafenib + trametinib (Tafinlar + Mekinist): For BRAF V600E-mutant anaplastic thyroid cancer. Both oral, Part D; combined retail > $20,000/month; $2,000 cap applies.

The 2025–2026 Part D redesign dramatically reduced the financial burden of high-cost oral cancer drugs. Previously, the “catastrophic coverage” phase required 5 percent coinsurance with no annual limit—on a $20,000/month drug, that meant $1,000/month indefinitely. The $2,000 cap transforms these drugs from financially ruinous to manageable. See Medicare Part D Explained for a complete breakdown of the Part D benefit redesign.

Thyroid Ultrasound

Diagnostic Ultrasound

A thyroid ultrasound ordered to evaluate a palpable nodule, goiter, or abnormal thyroid function is covered under Part B at 20 percent coinsurance:

• Outpatient radiology facility fee: 20 percent of the Medicare-approved amount
• Radiologist professional fee: 20 percent of the approved amount (often combined into a global fee)
• Total Medicare-approved charges: typically $200–$500; your 20 percent coinsurance = $40–$100

Ultrasound Surveillance for Thyroid Nodules

For patients with known thyroid nodules under active surveillance (American Thyroid Association guidelines recommend 12–24 month follow-up ultrasounds for most nodules), serial ultrasounds are covered under Part B when ordered by a physician with documentation of medical necessity. Each surveillance ultrasound generates a Part B claim with 20 percent coinsurance.

Ultrasound-Guided FNA Biopsy

Fine needle aspiration (FNA) biopsy of a thyroid nodule is the standard diagnostic procedure for nodules ≥1 cm with suspicious ultrasound features or ≥1.5 cm without suspicious features. It is covered under Part B:

• Ultrasound guidance: Part B imaging code, 20 percent coinsurance
• FNA procedure itself: Part B procedure code, 20 percent coinsurance
• Cytopathology (specimen analysis): Clinical laboratory, zero coinsurance

If molecular testing (Afirma, Thyroseq) is added to an indeterminate (Bethesda Category III/IV) cytology specimen, the molecular test is billed separately under Part B as a laboratory service.

Total out-of-pocket for an ultrasound-guided FNA biopsy without supplemental coverage: typically $150–$400 in 20 percent coinsurance charges (facility + physician + ultrasound guidance; pathology is zero).

Medigap Plan G: Covers all Part B coinsurance, so the biopsy costs you nothing beyond the annual $257 deductible.

Thyroid Surgery

Thyroid surgery—hemithyroidectomy (lobectomy) or total thyroidectomy—is performed for nodules that are cytologically indeterminate or malignant, symptomatic goiters, or hyperthyroidism refractory to medical management.

Outpatient Thyroidectomy

Most hemithyroidectomies and an increasing percentage of total thyroidectomies are performed on an outpatient or 23-hour observation basis:

• Hospital outpatient facility fee: Part B, 20 percent coinsurance
• Surgeon fee: Part B, 20 percent coinsurance
• Anesthesiologist fee: Part B, 20 percent coinsurance

Total Medicare-approved charges for an outpatient hemithyroidectomy: approximately $8,000–$15,000; your 20 percent coinsurance = $1,600–$3,000 without supplemental coverage.

Inpatient Thyroidectomy

For extensive total thyroidectomy with lymph node dissection (central compartment dissection, lateral neck dissection) for thyroid cancer, or for patients with significant comorbidities, inpatient admission may be appropriate:

• Part A hospital deductible: $1,676 per benefit period (2026)
• Surgeon fee: Part B, 20 percent coinsurance

Robotic Thyroidectomy

Robotic-assisted transaxillary thyroidectomy (scarless neck approach) is performed at selected centers. Medicare covers this technique under the same surgical codes as conventional thyroidectomy—no separate coverage determination required.

Parathyroid Monitoring and Calcium Supplementation

After total thyroidectomy, transient or permanent hypoparathyroidism requires monitoring and treatment. Lab tests (calcium, PTH, phosphorus, vitamin D) are clinical laboratory tests with zero cost-sharing. Calcium carbonate and vitamin D (cholecalciferol) supplements are not covered under Part D as OTC supplements. Prescription calcium citrate with vitamin D, if separately prescribed, may have limited Part D coverage. Prescription calcitriol (active vitamin D) for hypoparathyroidism is a covered Part D drug.

Radioactive Iodine (RAI) Therapy

Radioactive iodine-131 (I-131) is the primary treatment for:

1. Graves’ hyperthyroidism
2. Toxic multinodular goiter
3. Adjuvant treatment of differentiated thyroid cancer after total thyroidectomy
4. Treatment of thyroid cancer recurrence/metastases

RAI for Hyperthyroidism

RAI treatment for hyperthyroidism is administered as an oral capsule or liquid in a physician’s office or nuclear medicine suite. It is covered under Part B as a therapeutic nuclear medicine service:

• Professional fee (nuclear medicine physician or endocrinologist): 20 percent coinsurance
• Facility fee if performed at HOPD: 20 percent coinsurance
• Total Medicare-approved charges: typically $500–$1,500; your 20 percent coinsurance = $100–$300

RAI for Differentiated Thyroid Cancer

Post-thyroidectomy adjuvant RAI for thyroid cancer involves higher doses of I-131 and is performed under TSH stimulation (either thyroid hormone withdrawal or Thyrogen/recombinant TSH injection). High-dose RAI may require inpatient isolation under radiation safety protocols.

• Inpatient RAI: Admitted under Part A for radiation safety reasons. Part A deductible applies ($1,676 per benefit period). The I-131 itself is covered under Part A room and ancillary services.
• Outpatient RAI (lower doses, increasingly common): Covered under Part B.

Thyrogen (Thyrotropin Alfa) Injections

Thyrogen (recombinant human TSH) injections given before RAI therapy or thyroglobulin surveillance testing to stimulate TSH without thyroid hormone withdrawal are covered under Part B as physician-administered drugs:

• Two-injection protocol: Two daily IM injections administered in the physician’s office
• Medicare-approved amount: approximately $1,000–$2,000 per course
• Your 20 percent coinsurance: $200–$400 per course without supplemental coverage

Medigap Plan G covers this coinsurance.

Thyroid Cancer Surveillance

For differentiated thyroid cancer (papillary, follicular), long-term surveillance involves periodic:

1. TSH, thyroglobulin (Tg), and TgAb blood tests: Clinical laboratory tests, zero cost-sharing
2. Thyroid ultrasound: Part B, 20 percent coinsurance
3. Diagnostic whole-body iodine scan (WBIS): Nuclear medicine Part B, 20 percent coinsurance. May be done with Thyrogen stimulation.
4. PET-CT scan: Covered under Part B for restaging or surveillance when thyroglobulin is elevated but iodine scan is negative (FDG-avid disease)
5. CT of neck/chest/abdomen: Part B, 20 percent coinsurance for surveillance imaging

All laboratory components are zero cost-sharing; imaging studies are 20 percent coinsurance.

External Beam Radiation for Thyroid Cancer

For locally invasive thyroid cancer, anaplastic thyroid cancer, or medullary thyroid cancer, external beam radiation therapy (EBRT) may be indicated. EBRT is covered under Part B as outpatient radiation:

• IMRT or 3D-CRT course: 20 percent coinsurance on all fractions
• For anaplastic thyroid cancer (the most aggressive form), palliative EBRT may be combined with systemic therapy

Medicare Advantage Considerations for Thyroid Disease

For stable hypothyroidism requiring only annual lab monitoring and generic levothyroxine, Medicare Advantage plan differences are largely immaterial—costs are minimal either way.

For patients with thyroid cancer—particularly those receiving high-cost oral targeted agents (lenvatinib, selpercatinib), requiring complex surgery, or receiving adjuvant RAI—the MA vs. original Medicare decision deserves careful analysis:

• Targeted oral agents: MA plans cover these under the plan’s Part D benefit, subject to the same $2,000 cap. Formulary placement and prior authorization procedures vary.
• Complex thyroid surgery: For total thyroidectomy with neck dissection at a high-volume cancer center, confirm that the center is in-network for your MA plan. High-volume centers perform better outcomes at lower complication rates for thyroid cancer surgery.
• Prior authorization for RAI and Thyrogen: Some MA plans require PA for high-dose RAI and for Thyrogen injections. Ensure PA is obtained before scheduling treatment.

For thyroid cancer patients, a Medigap Plan G + original Medicare approach often provides more predictable costs and better access to specialist centers than Medicare Advantage. See Medicare Supplement vs. Advantage Costs for a full financial comparison.

Cost Summary by Thyroid Condition

Routine Hypothyroidism (Well-Managed)

For a well-managed hypothyroid patient on Medigap Plan G, total annual costs are essentially the Part B premium + Plan G premium + a nominal Part D copay.

Thyroid Nodule Surveillance

Post-Thyroidectomy Thyroid Cancer Surveillance

Key Takeaways

• All thyroid lab tests (TSH, T4, T3, antibodies, thyroglobulin) are covered under Part B as clinical laboratory tests at zero cost-sharing — no deductible, no coinsurance.
• Levothyroxine is a Tier 1 generic on nearly every Part D formulary, typically costing $0–$15/month.
• Thyroid ultrasound and FNA biopsy are covered under Part B at 20 percent coinsurance — Medigap Plan G eliminates this cost.
• Thyrogen injections are Part B physician-administered drugs covered at 20 percent coinsurance.
• RAI therapy is covered under Part B (outpatient low-dose) or Part A (inpatient high-dose).
• Oral targeted agents for thyroid cancer (lenvatinib, selpercatinib, dabrafenib, cabozantinib) are Part D drugs capped at $2,000/year out-of-pocket under the 2025–2026 Part D redesign — a major improvement over prior years.
• For thyroid cancer patients, Medigap Plan G combined with original Medicare provides the most predictable and lowest total cost for complex, multi-year treatment journeys.

For more context on managing medication costs under Medicare, see Medicare Part D Explained. For the broader picture of retirement healthcare budgeting, see Healthcare Costs in Retirement.