TSH (Thyroid Stimulating Hormone)
Measures TSH levels to assess thyroid function and screen for hyperthyroidism and hypothyroidism.
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This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland and acts as the master regulator of thyroid activity. When thyroid hormone levels in the blood drop below optimal, the pituitary responds by increasing TSH output, signaling the thyroid to ramp up production of thyroxine (T4) and triiodothyronine (T3). When thyroid hormones rise above the needed level, the pituitary pulls back on TSH, slowing the thyroid down. This feedback loop keeps the body's metabolic rate in balance.
T4 and T3 influence nearly every organ system, affecting heart rate, breathing, digestion, body temperature, weight regulation, and mood. Because TSH responds to even small shifts in thyroid hormone levels before those hormones themselves move outside the normal range, it is typically the first and most sensitive marker to become abnormal in developing thyroid disease. This makes TSH the standard first-line screening test for both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals experiencing unexplained changes in weight, energy levels, or mood that may indicate thyroid dysfunction
- Those with symptoms such as fatigue, cold intolerance, rapid heartbeat, anxiety, or sleep disturbances
- People with a family history of thyroid disorders, autoimmune conditions, or endocrine diseases
- Adults over 50-60 years old, particularly women, as part of routine health screening
- Individuals with other autoimmune conditions who may be at higher risk for thyroid problems
- Those taking medications that may affect thyroid function or considering thyroid hormone replacement therapy monitoring
What to expect
Preparation
Usually, people do not need to prepare for a TSH test. However, if the doctor is checking the blood for more than one issue, a person may need to fast or prepare in another way. The vitamin biotin (B7) can affect the results of the TSH test. If individuals take biotin, they should talk to their healthcare provider before having any thyroid function tests. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Sample Type
A small blood sample is drawn from a vein in the arm using a standard needle and collection tube.
Collection
When the needle is inserted to draw blood, some people feel moderate pain while others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. The blood draw typically takes just a few minutes at the laboratory.
Turnaround
Results are typically available within 1-2 business days after the sample reaches the laboratory.
Understanding your results
The generally accepted normal range for TSH falls between approximately 0.4 and 4.0 mU/L, though optimal ranges remain a topic of ongoing clinical discussion, and some laboratories use slightly different boundaries. Elevated TSH typically indicates hypothyroidism (the thyroid is underproducing and the pituitary is compensating by sending a stronger signal), while low TSH typically indicates hyperthyroidism (the thyroid is overproducing and the pituitary is backing off). However, an abnormal TSH result does not always indicate thyroid disease; age, pregnancy, medications, and non-thyroidal illness can all influence the value. Healthcare providers interpret TSH alongside symptoms, clinical history, and often additional tests like free T4 to confirm the diagnosis.
| Population | Reference Range | Notes |
|---|---|---|
| Adults (General) | 0.4-4.0 mIU/L | Most commonly accepted range, though some variation exists between laboratories |
| Adults (Alternative Range) | 0.5-5.0 mIU/L | Some laboratories use this slightly wider range |
| Elderly (70+ years) | Up to 6.0 mIU/L | Upper normal range may extend higher in elderly individuals |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
Low TSH levels most likely indicate that the thyroid gland is making excess thyroid hormone, a condition called hyperthyroidism or overactive thyroid. A variety of conditions lead to hyperthyroidism, including Graves' disease and thyroid nodules. Much more rarely, low TSH can be due to a problem with the pituitary gland. If a person's thyroid gland is secreting levels of hormones that are too high, the pituitary gland produces less TSH. Low TSH levels are associated with hyperthyroidism and increased metabolism in the body, with symptoms that may include weight loss, loose stools, high body temperature, high heart rate, irregular light periods, anxiety, irritability, and sleep problems.
What does a “High” result mean?
High TSH levels may indicate that the thyroid isn't making enough thyroid hormone, a condition called hypothyroidism or underactive thyroid. A number of conditions can cause hypothyroidism, including Hashimoto's disease. People develop hypothyroidism when their thyroid produces low levels of hormones, and when someone's thyroid gland does not produce enough hormones, the pituitary gland produces more TSH to compensate. High TSH symptoms are associated with a slowed metabolism and may include cold intolerance, slower heart rate, constipation, thinning hair, and depression.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your TSH test results are completely confidential and handled with the highest level of privacy protection. Results are <u>not reported to your doctor</u> unless you choose to share them, and they are <u>not part of your medical records</u> maintained by your primary care physician or health system. The test results will <u>not appear on insurance statements</u> or Explanation of Benefits (EOB) forms, ensuring your thyroid testing remains entirely private. Your personal health information is protected by strict confidentiality measures and is never shared with employers, insurance companies, or third parties without your explicit consent. You have complete control over who sees your results and how you choose to use this information. Many individuals appreciate this privacy when monitoring their thyroid health, especially when they want to understand their hormone levels before discussing them with healthcare providers or when managing ongoing thyroid concerns discreetly.
Frequently asked questions
Related tests
Free T4 (Thyroxine) Test
Often ordered alongside TSH to provide a complete picture of thyroid hormone production and function
View TestFree T3 (Triiodothyronine) Test
Measures the active form of thyroid hormone, helpful in diagnosing hyperthyroidism and monitoring treatment
View TestComprehensive Thyroid Panel
Includes TSH, Free T4, Free T3, and thyroid antibodies for complete thyroid health assessment
View TestTPO Antibodies Test
Helps identify autoimmune thyroid conditions like Hashimoto's disease when TSH levels are abnormal
View TestRelated conditions
Related articles
The Complete Guide to Thyroid Testing: Which Test Do You Actually Need?
Read ArticleWhat Does a High TSH Mean? (And What to Do Next)
Read ArticleTSH vs Full Thyroid Panel: Is the Cheaper Test Enough?
Read ArticleThe Connection Between Thyroid and Weight: What the Science Says
Read ArticleLast reviewed: April 2026
CPT Code: 84443
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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