What Is TSH and What Are Normal TSH Levels?

What Is TSH and What Are Normal TSH Levels

[Last updated 16th January, 2017]

TSH is a hormone that controls thyroid gland activity.

It’s typically used as a marker of thyroid health, but what are normal TSH levels?

This article explores what your TSH levels should be and how it relates to hypothyroidism.

What is TSH?

What is TSH?TSH is a hormone that controls thyroid function. It stands for Thyroid Stimulating Hormone.

It is actually produced by the brain’s pituitary gland, but stimulates production of the hormones triiodothyronine (T3) and thyroxine (T4) in the thyroid gland.

The amount and balance of these hormones affects almost every physiological process in the body, particular your body’s metabolism (1).

Summary: TSH is a pituitary hormone that stimulates or inhibits the production of thyroid hormones from the thyroid gland.

What Makes TSH Fluctuate?

The release of TSH is first stimulated by a hormone called TRH.

Once TSH makes its way to your thyroid, levels are largely dictated by the amount of T3 and T4 in your blood.

When T3 and T4 levels are low, the body produces more TSH to stimulate the thyroid. But when T3 and T4 levels are high, the body produces less (2).

TSH cycle

Image source. Click to enlarge.

Several other factors can also influence TSH levels:

  • Inflammation of the thyroid gland
  • Genetics
  • Deficiency or excess of iodine in the diet
  • Poisonous substances and radiation exposure
  • Pregnancy
  • Certain medications- antidepressants, cholesterol lowering drugs, chemotherapy drugs, steroids
  • Thyroid cancer

Summary: Current levels of thyroid hormone in the blood significantly dictates TSH levels, although there are other factors though to influence it too.

Hypothyroidism TSH Levels

Due to the symbiotic nature TSH has with thyroid hormones, TSH levels in the blood can theoretically be a good marker of thyroid health.

This TSH levels chart presents a simplified version of what different readings can indicate.

TSH Levels T3 and T4 Levels Disease Condition
High High Tumor of pituitary gland
Low Low Secondary hypothyroidism
Low High Grave’s disease
High Low Hashimoto’s disease

Those with Graves’ disease (an overactive thyroid) have high low TSH and subsequent high thyroid hormone levels. Hashimoto’s disease (underactive thyroid) is the opposite.

Summary: Low TSH typically indicates excessive thyroid hormone levels, while high TSH indicates thyroid hormone deficiency.

Normal TSH levels

Normal TSH levelsNormal TSH levels for the average adult range from 0.4 ‑ 4.0 mIU/L (milli-international units per liter) (3).

However, many organisations agree that a reading of 2.5 or less is truly ideal, with anything 2.5 – 4.0 mIU/L considered “at risk”.

For those on thyroxine, goal TSH level is between 0.5 to 2.5 mU/L.

The reference ranges alter slightly as we grow older and if you are pregnant:

TSH levels for premature birth (28‑36 weeks)

  • 0.7‑27 mIU/L

TSH levels for children

  • Birth to 4 days: 1‑39 mIU/L
  • 2‑20 weeks: 1.7‑9.1 mIU/L
  • 21 weeks to 20 years: 0.7‑64 mIU/L

TSH levels for adults

  • 21‑54 years: 0.4‑4.2 mIU/L
  • 55‑87 years: 0.5‑8.9 mIU/L

TSH levels during pregnancy

  • First trimester: 0.3‑4.5 mIU/L
  • Second trimester: 0.3‑4.6 mIU/L
  • Third trimester: 0.8‑5.2 mIU/L

Small variations in results can occur depending on the laboratory and its methods used, as well as the time of day your blood was taken.

Summary: Normal TSH levels range from 0.4 ‑ 4.0 mIU/L for the average adult.

High TSH Levels

High TSH levelsA TSH reading above 4.0 mIU/L is considered high (elevated).

High TSH levels typically indicates an underactive thyroid gland, which produces too little thyroid hormone. This is known medically as hypothyroidism.

Common causes of hypothyroidism include an autoimmune disease (known as Hashimoto’s disease), radiation treatment, or surgical removal of the thyroid gland.

Replacing thyroid hormone and altering your diet are crucial for the safe and effective treatment of an underactive thyroid.

Summary: High TSH levels for the average adult are 4.2 mIU/L and over. This reading typically indicates an underactive thyroid.

Low TSH levels

normal TSH levelsA TSH reading below 0.4 mIU/L is considered low.

Low TSH levels typically indicates an overractive thyroid gland, which produces too much thyroid hormone. This is known medically as hyperthyroidism.

It can be caused by an autoimmune disease (known as Graves’ disease), goiter, excessive iodine in the body, or an overdose of synthetic thyroid hormone.

Initial hyperthyroidism treatment can involve anti‑thyroid medications and radioactive iodine to slow down thyroid hormone production. Most respond well to hyperthyroidism medications and are treated successfully.

Summary: Low TSH levels for the average adult are less than 0.2 mIU/L. This reading typically indicates an overractive thyroid.

The Problem With Relying on TSH

normal TSH levelsTSH is the most well-studied marker for judging thyroid health and function.

It has been the gold standard test for decades, and is considered the most sensitive and accurate indicator by most endocrinologists and other doctors.

However, more recent research indicates our systematic reliance on TSH is missing the mark. This leaves a lot of hypothyroid cases either misdiagnosed or undiagnosed.

Some clinical studies have found that both T3 and TSH levels can decline at the same time, particularly in obese individuals that lose weight (4, 5).

That means T3 levels can be low, yet TSH will remain in the normal range.

Certain medications, such as metformin, are also known to independently lower TSH levels in diabetics and PCOS patients with thyroid issues (6).

These variables are just the tip of the iceberg, but highlight why TSH is not completely reliable on its own. Considering the pituitary gland (which produces TSH) is unique in its function, it makes sense that some metabolic processes and outside stressors can influence TSH activity.

This is something to discuss with your doctor if your TSH readings are high-normal, yet you still feel seriously unwell.

Summary: Several external stressors are known to influence TSH levels, independently of thyroid hormone levels. This means TSH on it’s own is not always a reliable indicator of thyroid health.

TSH Tests at Home

It’s not uncommon for doctors to skip over TSH testing if they do not believe there is a thyroid issue.

Fortunately, there is reliable way to measure TSH yourself with a home-testing kit. It’s FDA approved to be as accurate as a blood draw test, and results are sent direct to you by email or phone call.

Click here to take a look on Amazon (aff link).

Have a read of the interesting reviews, as there’s the occasional comment that results are slow to get back.

Additional Tests For Thyroid Health

Given the potential inaccuracies with TSH on its own, comprehensive screening of thyroid health should ideally include these 6 tests:

  • TSH
  • Free T3
  • Free T4
  • Reverse T3
  • Thyroid Peroxidase Antibodies
  • Thyroglobulin Antibodies

Your doctor should be aware of these tests.

Further Reading

What is T4 and T3: The Complete Guide
How To Lose Weight With An Underactive Thyroid: Your 6-Step Guide
14-Day Meal Plan For Hypothyroidism And Weight Loss
Hashimoto’s Disease: Your Guide For Living With Hypothyroidism

More on hypothyroidism and related topics

TSH is a hormone that controls thyroid gland activity. This article explores what normal TSH levels are and how it relates to hypothyroidism.


  1. Hi joe I’m a lifting guy although I hate taking some suppliment but I’m more concerned about nutrition and healthy eating as well..so what can I eat or do to increase my growth and development of muscles as well?

  2. Biswanath Neogi says:

    My wife (56 yrs old) is taking Eltroxine 100 mcg for last 15 years and now blood test indicates the following result
    T3 – 1.56, T4 – 10.93, TSH- 0.29.: , ANTI TPO ANTIBODY 135, ANA NEGATIVE.
    Doctor suggested to take TPU Tabs 50mg twice daily.her weight has also decreased . Can you suggest if medicines prescribed is suitable at this stage.

  3. Biswanath Neogi says:

    My wife (56 yrs old) is taking Eltroxine 100 mcg for last 15 years and now blood test indicates the following result
    T3 – 1.56, T4 – 10.93, TSH- 0.29.: , ANTI TPO ANTIBODY 135, ANA NEGATIVE.
    Doctor suggested to take PTU Tabs 50mg twice daily.her weight has also decreased . Can you suggest if medicines prescribed is suitable at this stage.

  4. swati gokhale says:

    My T3 92.4 T4 6.30 TSH 18.30 high

  5. I,Nargis Parvin,aged about 37, am taking Eltroxin 75mcg for 7 yes. Now the rate of tsh is 3.4 mcu/ml. What can do now? Carry on taking the tab or change?

  6. My TSH is 94.66 kindly advise?
    Age – 36
    Waight- 70 kg
    I am female

  7. I’m Nita, three months short of 69 years, a healthy and active, if very thin, woman with no history of diabetes or BP. A Test done on me a fortnight ago at about 2pm states my TSH levels to be 7.14 uIU/ml. My T3 total and T4 total are shown to be normal at .89 ng/ml and 6.60 ug/dl. Do I have hypo thyroidism?…Thanks in advance. Nita

  8. Hello. I am 29 and my t3 is 105.5 T4 is 5.3 and TSH is 10.89 ulU/mLand have been adviced to take Thyronorm 50. And i weigh 60kg . Do i have hypothyroidism ?

  9. Hello, I just got my test results back and my TSH result came back as 0.005 telling me it was below low normal. I’m 36 years old and not sure if this should be a concern for me. My Doctor ordered a thyroid scan. Should I be concerned at the result that came back? My Doctor did not explain much, though she did state I have hyperthyroidism. Don’t know what to think about this. Thank you!

  10. my wife tsh level 10.53 please give me advice .this is normal or high?

  11. I am 53 years old.i am on tyronorm for the last 10 years.presently i am on 75 mcg tyronorm.my tsh level presently is 0.044. What would be the right amount of tyronorm mcg for me?

  12. Betty Iniguez says:

    Hi Joe! I’m 46 years old and was recently diagnosed with hypothyroidism in June of this year. My most recent labs from 8/24, were all within the “normal range” but I know they are not where they should be:
    TSH-Icma 0.93
    T-3, Serum 77
    Free T-3 2.3
    Free T4 1.2
    Thyroglobulin Antibody <1.0
    Thyroid Peroxidase (Tpo) Ab 6
    Following my most-recent lab results, I was switched from Synthroid (50 mcg)/Liothyronine (5mcg 2 x's daily) to Nature-throid 48.75 mcg which I started two weeks ago. My biggest concern is my body won't respond to diet, even after I cut out everything processed, sugar, starch, dairy, liquor.
    I'm taking an adrenals saliva test tomorrow and just requested a hormone panel, and a review of my Glucose, Serum which has dropped to 92 but was in the pre-diabetic range when I started the thyroid meds (99). My fatigue is improving but I'm too tired to workout. I've always been in good shape and had a good metabolism so all of this is very frustrating and depressing. Is there anything in particular I should be tested for? My dr did mention I'm not premenopausal.

  13. Adelia Singh says:

    I am female, 64 years old. My TSH is .083 uTU/ml. My appointment with my doctor is still on oct. 5. What should i do?

  14. I had my thyroid removed many years ago and recently a Dr. said my TSH level was too high. It was .003. can you tell me what a normal range is?

  15. carmen ayala says:

    What if your TSH level is 0.231

  16. Claire Gibbs says:

    Hi Joe, very interesting reading however I had my thyroid removed over 10 years ago due to Graves Disease and have been taking levothroxine since then, however, when I changed area and doctor, even though I have regular blood tests and have been back to see the endocrinologist, they tell me my levels are fine, although I feel very sleepy and have put on two stone in weight, which I am struggling to lose. any ideas to help?

  17. Hi just diagnosed with hashimoto s and don’t want to start taking hormone until ive exhausted diet changes. I’ve been told you can put into remission with a type of paleo diet . I’m away for 6 weeks and will do this when I get back from India . Have you heard this is possible or taking hormone while putting in remission is way to go

  18. Hi, Im Criz 34 years old, female, my TSH result is 0.270 miu/L is this okay? Thanks

  19. LorettaAnderson says:

    My TSH result is 0.022 , so thyroid is under active ? , just started levothryroxine 137 dose , what to expect ? Thanks

  20. Just got my Tsh test 4.04 mIU/L I am 57 yr old female is this high?

  21. Deva Christy says:

    My TSH is 27.88 & T4 9.87 kindly advise? Age – 33 Waight- 58 kg I am female

  22. Julie Hendricks says:

    I’m female, 56, 5’2″, 107 lbs. I’m confused about my labs. My free T3 is 6.4, T3 total is 2.8, my free T4 is 0.78 and my TSH is 29.98. I know the TSH is too high but am not sure what all of it taken as a whole signify. Any input appreciated, thx.

  23. chandrika shetty says:

    my two children having hypothyroid , myself iam having same problem .my children one is 18years and oterone having 13 years

  24. Hi, I’m Darlene and have been fighting hashi’s since around 2003. My levels rarely are on point but recently in the last 6 months they are near and over 100, most recently yesterday was 96.4. What are the major complications at this level and is there a risk for coma?

  25. Hey,
    I am Garima and recently I got to know after a blood test that my t3 and t4 levels are normal bt my tsh is 5.2… What should I do..

  26. Hey,
    I am Garima and recently I got to know after a blood test that my t3 and t4 levels are normal bt my tsh is 5.2… What should I do.. What Are The Possible causes And Effects Of This . . Are There Any Other Tests I ShouLd Consider .

  27. i am 58 my tsh is 0.92 what weight loss plan should i follow

    T3 (Triiodothyronine) – Total
    (Serum/Chemiluminescent Immunometric Assay
    0.99 ng/mL 0.60 – 1.81
    T4 (Thyroxine) – Total
    (Serum/Chemiluminescent Immunometric Assay
    10.6 µg/dL 3.5 – 12.6
    TSH (Thyroid Stimulating Hormone)
    (Serum/Chemiluminescent Immunometric Assay
    14.32 µIU/mL 0.35 – 5.50


  29. mukeshpandey says:

    Tsh *4.66 uiu/ml brr 0.27-4.20uiu/ml
    Mrs karuna pandey age 29

  30. Hiiii . I m amreen 26 years old. My TSH result 3.13… I takes thyroid tablet take or not

  31. cathy beije says:

    6.660 u[IU]/mL (High) My lat reading of lab work last week.Can’t seem to get a control on this, suggestion? on meds!

  32. Hi I’m darrah my TSH level is 0 .124 uiU what should I do to increase it.i am taking Carbimazole as prescribed by my dr

  33. Judy Olson says:

    I am curious as to why the TSH range, for adults, changes so dramatically after age 55.

    I am 57 years old with a TSH of 3.8, which sounds like I should be right on target, but it seems like the normal range is huge. I have several symptoms, like dry skin and hair, muscle weakness, tingling sensations in my legs and feet, joint and muscle pain and I haven’t slept well, in years.

    I’m concerned that the range may not be telling the whole story. Since there is no personal baseline TSH number, how do I know that my test results are truly normal. Maybe my true normal is .8.

  34. Hi
    My name is jaleh I’m 45 years old
    Tsh 3.5
    T4. 1.2
    Do you think i must use tablet ?please advise me thank you

  35. Hey i m 56yr old women and my TSH is 10.22, wieght 66..what to do m feeling uneasy since 10-12 days not feeling to eat anything

  36. Rekha sharma says:

    Hey i am rekha my t3 is 116.00 and t4is 9.27 and tsh highlight by 4.540 so please advice me what a issue in tsh pls advice.

  37. surender singh says:

    my wife’s Thyroids test result are ….
    TSH- less than 0.004

    please suggest ../ advise…medication..

  38. I am 27 years old Male and I had a problem of hair fall. When I visited my Dermatologist, she told me to get checked the Thyroid profile. What I found in this test is that Serum T3 and T4 are within the normal range where as Serum TSH is 13.2mIU/L whereas the nornal range of Serum TSH is between 0.465-4.68. Please advise is there anything to worry about or not?

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