The Thyroid-Stimulating Hormone (TSH) test is a blood analysis that measures the amount of TSH produced by the pituitary gland. TSH regulates the production of thyroid hormones, which control the body’s metabolism and energy use. The TSH test is the primary indicator for screening and diagnosing thyroid disorders, such as hyperthyroidism or hypothyroidism. Medicare coverage for TSH testing under Part B is not automatic and requires a determination of medical necessity.
Establishing Medical Necessity for Medicare Coverage
Medicare defines medical necessity as services or items required for the diagnosis or treatment of an illness or injury. To be covered, a physician must order the TSH test to diagnose an illness, monitor an existing disease, or track the effectiveness of a treatment plan. The Centers for Medicare and Medicaid Services (CMS) establishes these coverage rules through National Coverage Determinations (NCDs).
Coverage is also governed by Local Coverage Determinations (LCDs), which are specific policies created by regional Medicare Administrative Contractors (MACs). Both NCDs and LCDs dictate which services are payable based on the patient’s condition, which is communicated through specific International Classification of Diseases, Tenth Revision (ICD-10) codes submitted on the claim form. A TSH test ordered without a corresponding diagnosis code indicating a medical reason will generally be denied coverage.
Specific Conditions That Justify TSH Testing
The most common diagnoses justifying Medicare coverage are those directly related to thyroid gland function. The test is medically necessary to confirm or rule out primary hypothyroidism (an underactive thyroid) or primary hyperthyroidism (an overactive thyroid). It is also covered to distinguish between primary hypothyroidism and secondary hypothyroidism, where the problem originates in the pituitary gland.
For patients with known thyroid conditions, such as goiter, thyroid nodules, or thyroid cancer, the TSH test is covered to monitor hormone levels and disease progression. Coverage also extends to tracking the effectiveness of drug therapy for patients receiving treatment for hypothyroidism (e.g., levothyroxine) or hyperthyroidism (e.g., antithyroid medications).
The test is also covered when a patient presents with symptoms or conditions potentially caused by thyroid dysfunction. These associated conditions include metabolic disorders, unexplained hyperlipidemia, and certain types of anemia. Unexplained symptoms like cardiac arrhythmias, chronic fatigue, or significant weight changes may warrant a TSH test to investigate a potential thyroid component. The provider’s documentation must clearly link the patient’s symptoms or other diagnoses to the need for thyroid function evaluation.
Non-Covered Uses and Routine Screening Exclusions
Medicare Part B coverage is strictly limited to services necessary for the diagnosis or treatment of an illness or injury. Consequently, TSH testing performed as routine screening for asymptomatic patients is generally excluded from coverage. This exclusion applies when the test is ordered as a general wellness check without documented signs, symptoms, or a prior history suggesting thyroid dysfunction.
Federal law excludes payment for routine physical examinations and services not intended for diagnosis or treatment. Ordering a TSH test simply as a preventative measure, without a documented medical indication, will result in a denial of the claim. If the provider is unsure if Medicare will cover the test, they may issue an Advance Beneficiary Notice of Noncoverage (ABN) to the patient. This notice informs the patient that they may be financially responsible if Medicare denies the claim due to lack of medical necessity.
Frequency Limitations for Ongoing Monitoring
Once a diagnosis is established and treatment is initiated, Medicare covers TSH testing for ongoing monitoring within limits of medical reasonableness. For patients with a clinically stable thyroid condition, testing is typically covered up to two times per year. This frequency ensures hormone levels remain within the therapeutic range and reflects the standard of care for long-term management.
More frequent testing is considered medically necessary when the patient’s clinical status is unstable or if the treatment plan has recently changed. For example, if a physician adjusts the dosage of thyroid hormone replacement medication, more frequent TSH measurements are required to assess the effectiveness of the new dose. Additional testing beyond the typical two-per-year limit is also permissible if a patient develops new or worsening symptoms of hyperthyroidism or hypothyroidism.