Thyroid · Blood test
TSH thyroid test: normal range explained
Also printed as: Thyroid Stimulating Hormone, TSH Ultrasensitive, Thyrotropin
TSH, thyroid-stimulating hormone, is made by the pituitary gland and tells the thyroid how much hormone to make, so the blood test is usually the first thyroid check. MedlinePlus prints an adult range of 0.4–4.8 µIU/mL and Testing.com 0.40–4.50; Indian labs often print a wider range, but the range printed on your own report is the one that applies.
Last updated 5 sources
What is the normal range for TSH?
| Printed for | Range |
|---|---|
| Adults, as MedlinePlus prints it | 0.4–4.8µIU/mL |
| Adults 20 and over, as Testing.com prints it | 0.40–4.50mIU/L |
Reference ranges vary between laboratories. Always use the range printed on your own report. Why ranges differ between labs
Sources:MedlinePlus, Testing.com
What does TSH measure?
The thyroid is a small gland at the front of the neck whose hormones set how the body uses energy, affecting heart rate, weight, digestion and mood. The pituitary gland in the brain makes TSH, also called thyrotropin, which signals the thyroid how much hormone to produce.
The two work as a feedback loop: when thyroid hormone is low, the pituitary makes more TSH, and when thyroid hormone is high, it makes less. Because of this loop, TSH is usually the first thyroid test a doctor orders.
Sources:MedlinePlus, Testing.com
Why do doctors order the TSH test?
Doctors order TSH to find out whether the thyroid is overactive or underactive, to set and check the amount of thyroid medicine a person takes, to follow treatment for an overactive thyroid, and to look into lumps in the thyroid. On its own it shows that something is off, not why.
Symptoms that prompt the test include tiredness, weight change, feeling unusually cold or hot, a fast or irregular heartbeat, dry skin, hair thinning, constipation or diarrhoea, and irregular periods or fertility problems. An abnormal TSH is usually followed by free T4, sometimes free T3, and thyroid antibody tests.
Sources:MedlinePlus, Lab Tests Online UK
What can change your TSH result?
TSH shifts with the time of day, pregnancy, illness, age and several medicines and supplements.
- TSH varies through the day; MedlinePlus says it is best to have the test early in the morning, and Testing.com notes the swing is usually small.
- Biotin (vitamin B7) supplements can interfere with the test; Testing.com advises stopping biotin at least 72 hours before the draw, and MedlinePlus says to tell your provider if you take it.
- TSH is often slightly low in the first three months of pregnancy, and pregnancy has its own ranges for each trimester.
- A serious illness unrelated to the thyroid can briefly lower TSH, and extreme stress can affect it.
- TSH may be higher in people over 80 without thyroid disease, and some labs use a higher upper limit for older people.
- Amiodarone, lithium, dopamine, potassium iodide and steroid medicines such as prednisone can change TSH, as can thyroid hormone itself. Do not stop a medicine unless your doctor tells you to.
- After a change in thyroid medicine, TSH takes time to settle; Lab Tests Online UK advises waiting at least six weeks before rechecking.
How do you read TSH on your lab report?
TSH is usually the first line of a thyroid profile, printed as TSH, TSH ultrasensitive or thyroid stimulating hormone, in µIU/mL, uIU/mL or mIU/L. Those units give the same number: Testing.com's chart shows one lab printing 0.450–4.500 uIU/mL and another 0.40–4.50 mIU/L for the same test.
Printed ranges vary: MedlinePlus prints 0.4–4.8 µU/mL, Testing.com 0.40–4.50 mIU/L for adults aged 20 and over, with separate trimester rows in pregnancy, and some labs use an upper limit as high as 7 for older people. Read your value against the row printed for you, with the free T4 and free T3 lines on the same report.
Amara reads TSH with the range printed beside it on each report, flags a value outside that range, and shows what changed since your last report. Try it with two sample reports
A sample Amara row for TSH: 5.6 µIU/mL on 19 Feb 2026 at Lab A (sample), then 3.9 µIU/mL on 2 Sep 2026 at Lab B (sample), each with its lab's printed range.
Sources:MedlinePlus, Testing.com
Questions people ask about TSH
Is TSH ultrasensitive the same as TSH?
TSH ultrasensitive is the same hormone measured with a more sensitive method. Testing.com explains that current labs use third-generation, highly sensitive assays that can detect TSH down to 0.01 mIU/L, which helps pick up a suppressed TSH. Labels such as ultrasensitive, ultra TSH or highly sensitive TSH on an Indian report all refer to this test.
Is a TSH test the same as a thyroid profile?
Can biotin affect thyroid test results?
Biotin can affect thyroid test results. MedlinePlus says biotin, also called vitamin B7, can affect TSH results and advises telling your provider before thyroid tests, and Testing.com advises stopping biotin supplements at least 72 hours before the blood draw. Check the label of any supplement you take, since biotin is a common ingredient.
Do I need to fast before a TSH test?
Fasting is not needed for a TSH test; Testing.com says fasting does not affect TSH. MedlinePlus adds that you may need to fast for several hours if other blood tests share the sample, and suggests an early-morning draw because TSH varies through the day. Follow the instructions on your own test form.
What can a high TSH result mean on my report?
A high flag on TSH means the value sits above the range that lab printed. The sources say doctors most often read a high TSH as a sign the thyroid is underactive, but illness, age over 80, biotin and some medicines can also move it, and ranges differ by lab. Your doctor reads it with free T4.
Sources
- TSH (Thyroid-stimulating hormone) TestMedlinePlus · medlineplus.gov · Opened
- TSH testMedlinePlus · medlineplus.gov · Opened
- TSH Test: Order a Thyroid Blood Test OnlineTesting.com · testing.com · Opened
- Thyroid-Stimulating Hormone (TSH)Lab Tests Online UK · labtestsonline.org.uk · Opened
- Thyroid Test Results Chart: How to Read Your ResultsTesting.com · testing.com · Opened
About this page
Every statement on this page comes from the sources listed above. Ranges are those commonly printed on Indian lab reports; the range printed on your own report is the one that applies.
Published by Amara Health, a product of MetaNova AI Private Limited, Hyderabad.
Amara Health does not provide medical advice, diagnosis or treatment. Information shown by Amara is based on available health records and may contain errors. Review important information against the original report and consult a qualified healthcare professional for medical decisions. Do not use Amara for medical emergencies.
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