Other names: TSH 3rd Gen, TSH, 3rd generation, THYROID STIMULATING HORMONE, TSH, High Sensitivity, TSH W/REFLEX TO FT4, TSH, THIRD GENERATION, Thyroid Stimulating Hormone (TSH)
Thyroid-Stimulating Hormone (TSH) is essential for your body's thyroid health and overall metabolism. Measuring TSH levels is often the first step in diagnosing hypothyroidism, hyperthyroidism, and subtle thyroid imbalances.
In this guide, you’ll learn how to interpret TSH levels, what factors can influence your test results, and what to do if your numbers fall outside the normal range.
TSH (Thyroid-Stimulating Hormone), or thyrotropin, is produced by your pituitary gland to regulate thyroid function. It signals your thyroid to release T3 (triiodothyronine) and T4 (thyroxine)—hormones that control metabolism, energy, heart rate, and mood.
The hypothalamus, pituitary, and thyroid create a feedback loop: if thyroid hormone levels drop, TSH rises to stimulate the thyroid, and vice versa.
| Condition | TSH Range (mIU/L) |
|---|---|
| Hyperthyroidism | 0 – 0.4 |
| Normal (Euthyroid) | 0.4 – 4.0 |
| Mild Hypothyroidism | 4.0 – 10.0 |
| Hypothyroidism | >10.0 |
Use your laboratory's specific reference ranges and always consult with a healthcare provider.
| Population or Condition | TSH Range (mIU/L) |
|---|---|
| 1–2 Days Old | 3.20–34.60 |
| 3–4 Days Old | 0.70–15.40 |
| 5 Days–4 Weeks | 1.70–9.10 |
| 1–11 Months | 0.80–8.20 |
| 1–19 Years | 0.50–4.30 |
| Adults (Non-Pregnant) | 0.40–4.50 |
| Pregnancy–1st Trimester | 0.26–2.66 |
| Pregnancy–2nd Trimester | 0.55–2.73 |
| Pregnancy–3rd Trimester | 0.43–2.91 |
Action: If TSH results don’t match your symptoms, repeat testing at the same lab and while fasting.
Heterophile Antibodies: From animal-derived medicines or transfusions can skew results.
Thyroid Autoantibodies: Can alter TSH even without thyroid disease.
Action: If TSH and Free T4 are inconsistent, ask your doctor for antibody testing (e.g. anti-TPO, anti-Tg).
Common offenders:
Corticosteroids
Amiodarone
Lithium
High-dose Biotin
Iodine-rich supplements
Action: Tell your doctor about all meds and supplements. You may need to pause some (like Biotin) for 48 hours before testing.
TSH peaks in early morning and lowers later in the day.
Action: Test early morning (7–9am), fasting for reliable results.
Non-thyroidal illness syndrome can temporarily lower TSH.
Action: Delay TSH testing until recovered from acute illness or stress.
The hCG hormone during pregnancy lowers TSH.
Action: Always use trimester-specific reference ranges for pregnant women.
| Symptom |
|---|
| Rapid heartbeat |
| Weight loss, increased appetite |
| Anxiety, irritability |
| Heat intolerance |
| Symptom |
|---|
| Fatigue, sluggishness |
| Weight gain |
| Cold intolerance |
| Dry skin, constipation |
| Depression |
TSH is an important first marker, not the whole story: Always assess TSH with Free T4, Free T3, and your symptoms.
Treat symptoms, not just numbers: Fatigue, weight changes, and mood should guide decisions, not labs alone.
Consistent timing is vital: Always test at the same time of day under similar conditions.
Follow-up matters: If your TSH is borderline or abnormal, re-test after any lifestyle change or after starting treatment.
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High levels of Thyroid Stimulating Hormone (TSH) typically indicate an underactive thyroid, commonly referred to as primary hypothyroidism or subclinical hypothyroidism. When thyroid hormones (T3 and T4) are low, the hypothalamus and pituitary gland increase TSH production to stimulate the thyroid. Elevated TSH levels can signify a range of thyroid-related conditions, each with unique causes, symptoms, and treatment options.
TSH reference ranges can vary between laboratories and age groups. For adults, the general normal range is 0.4–4.0 mIU/L, although some experts suggest an upper limit of 2.5 mIU/L for optimal thyroid health. During pregnancy, TSH levels are typically lower:
Symptoms of hypothyroidism, associated with elevated TSH, vary depending on severity. Common signs include:
Insufficient production of thyroid hormones by the thyroid gland.
Mild hypothyroidism with elevated TSH but normal T3 and T4 levels, often asymptomatic.
Temporary thyroid dysfunction, often following thyroiditis or viral illness.
Chronic inflammation caused by the immune system attacking the thyroid gland.
Both iodine deficiency and excess can impair thyroid function.
Medications like lithium or amiodarone can interfere with thyroid hormone production.
Surgical removal or radioactive iodine treatment can lead to hypothyroidism due to reduced thyroid tissue.
Conditions present from birth, such as thyroid agenesis or hormone synthesis defects.
A rare genetic disorder where body cells are resistant to thyroid hormone.
To confirm thyroid dysfunction, your doctor may order the following tests:
Treatment varies based on the cause and severity of symptoms:
Certain substances can interfere with levothyroxine absorption, including:
Always inform your doctor about all medications and supplements.
Regular monitoring is essential:
Adjustments to medication dosage may be needed due to changes in weight, age, or overall health.
Managing elevated TSH involves more than just medication:
By following these guidelines and working closely with your healthcare provider, most individuals with elevated TSH levels can effectively manage their condition and maintain a high quality of life.
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I have been using Healthmatters.io since 2021. I travel all over the world and use different doctors and health facilities. This site has allowed me to consolidate all my various test results over 14 years in one place. And every doctor that I show this to has been impressed. Because with any health professional I talk to, I can pull up historical results in seconds. It is invaluable. Even going back to the same doctor, they usually do not have the historical results from their facility in a graph format. That has been very helpful.
Karin
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What fantastic service and great, easy-to-follow layouts! I love your website; it makes it so helpful to see patterns in my health data. It's truly a pleasure to use. I only wish the NHS was as organized and quick as Healthmatters.io. You've set a new standard for health tracking!
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As a PRO member and medical practitioner, Healthmatters.io has been an invaluable tool for tracking my clients' data. The layout is intuitive, making it easy to monitor trends and spot patterns over time. The ability to customize reports and charts helps me present information clearly to my clients, improving communication and outcomes. It's streamlined my workflow, saving me time and providing insights at a glance. Highly recommended for any practitioner looking for a comprehensive and user-friendly solution to track patient labs!
A low TSH (Thyroid-Stimulating Hormone) level often indicates that the body has an elevated amount of thyroid hormones (T3 and T4). However, this is not always the case. While hyperthyroidism is the most common cause, a low TSH can also point to less obvious conditions.
Low TSH typically reflects high thyroid hormone levels, but exceptions exist.
It’s frequently associated with hyperthyroidism (overactive thyroid).
In some cases, low TSH may indicate central (secondary) hypothyroidism, where the issue originates from the pituitary gland or hypothalamus, not the thyroid itself.
If you have low TSH but normal T3 and T4 levels, you may be dealing with subclinical hyperthyroidism. This is a mild, often symptomless form of hyperthyroidism that still requires monitoring, as it can affect heart health and bone density over time.
→ Read our in-depth article on Subclinical Hyperthyroidism
Several specific conditions and factors can suppress TSH production:
An autoimmune condition where antibodies overstimulate the thyroid, causing it to produce excess hormones.
Inflammation of the thyroid gland, which can temporarily release stored thyroid hormones into the bloodstream. Types include:
Postpartum Thyroiditis
De Quervain's (subacute) Thyroiditis
A non-thyroidal illness that disrupts normal thyroid function tests during acute or chronic systemic illness, often showing low TSH.
Overmedication with levothyroxine (T4) or liothyronine (T3) can suppress TSH levels.
Excessive iodine intake, from diet or medical imaging contrast agents, can overstimulate the thyroid.
Autonomously functioning thyroid nodules that produce thyroid hormones independently of TSH regulation.
The heart medication amiodarone, which contains high iodine levels, can disrupt normal thyroid function, leading to either hypothyroidism or hyperthyroidism.
Confirm with Additional Testing: Request Free T3, Free T4, and thyroid antibody tests for a clearer diagnosis.
Evaluate Symptoms: Discuss symptoms like palpitations, weight changes, anxiety, or fatigue with your healthcare provider.
Review Medications and Supplements: Ensure your doctor knows if you’re taking thyroid medications, iodine supplements, or drugs like amiodarone.
Assess Pituitary Function: If T3 and T4 are low or normal despite low TSH, pituitary dysfunction (central hypothyroidism) should be considered.
Schedule Follow-Up Monitoring: For subclinical cases, regular testing every 3–6 months may be recommended.
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Anthony
Unlimited Plan Member since 2021
I have been using Healthmatters.io since 2021. I travel all over the world and use different doctors and health facilities. This site has allowed me to consolidate all my various test results over 14 years in one place. And every doctor that I show this to has been impressed. Because with any health professional I talk to, I can pull up historical results in seconds. It is invaluable. Even going back to the same doctor, they usually do not have the historical results from their facility in a graph format. That has been very helpful.
Karin
Advanced Plan Member since 2020
What fantastic service and great, easy-to-follow layouts! I love your website; it makes it so helpful to see patterns in my health data. It's truly a pleasure to use. I only wish the NHS was as organized and quick as Healthmatters.io. You've set a new standard for health tracking!
Paul
Healthmatters Pro Member since 2024
As a PRO member and medical practitioner, Healthmatters.io has been an invaluable tool for tracking my clients' data. The layout is intuitive, making it easy to monitor trends and spot patterns over time. The ability to customize reports and charts helps me present information clearly to my clients, improving communication and outcomes. It's streamlined my workflow, saving me time and providing insights at a glance. Highly recommended for any practitioner looking for a comprehensive and user-friendly solution to track patient labs!
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Anti-Thyroglobulin ab. (0-39), Antithyroid Antibody, Free Thyroxine, Free Thyroxine Index, Parathyroid Hormone (PTH), Serum, PTH ANTIBODY, Reverse T3, Serum, T3 - Triiodothyronine (ng/mL), T3, Free (Triiodothyronine), T4, Free, T4, Total (Thyroxine), Thyroid Peroxidase Antibodies (Anti-TPO Ab), Thyroid Stim Immunoglobulin, Thyroid-Stimulating Hormone (TSH), Total T3, TRAb (TSH Receptor Binding Antibody), Triiodothyronine (T3) Uptake
