TSH Levels During Pregnancy: What’s Healthy & Normal?

TSH Levels During Pregnancy: What’s Healthy & Normal?

Pregnancy puts extra strain on thyroid function. 

This is especially true if you suffer from thyroid conditions such as hypothyroidism or Hashimoto's. 

If you fit into this category then you should pay special attention to your thyroid numbers while you are pregnant. 

This article is devoted to that topic. 

I want to share with you the importance of understanding your TSH level during pregnancy, why it is different from non-pregnant women, and what factors influence it. 

Let's jump in: 


TSH Levels During Pregnancy Chart by Trimester

Believe it or not, pregnancy actually promotes a fairly big problem for many women around the globe. 

Hypothyroidism is an increasingly common hormone imbalance and its one that affects almost every system and hormone in your body. 

This situation is complicated by pregnancy because as your body becomes pregnant you place increased demand on your thyroid function. 

This means that the standard ways that we look and assess thyroid function during pregnancy have to change. 

We know that during pregnancy your thyroid gland grows in size and your free thyroid hormones should increase by about 50% (1). 

TSH in pregnant women

The reason for this is simple:

Your body must produce thyroid hormone for both you and your child while they are developing. 

Knowing that pregnancy impacts reference ranges for thyroid lab tests, some associations have created new reference ranges specifically for women who are pregnant.

Standard TSH levels during Pregnancy:

  • First trimester: 0.1 to 2.5 mU/L
  • Second trimester: 0.2 to 3.0 mU/L
  • Third trimester: 0.2 to 3.0 mU/L

These reference ranges are for the thyroid lab test TSH (which we will discuss more below) and they are considered to be tighter when compared to healthy people and women who are not pregnant. 

You can compare these ranges to those which are normally used:

You can see from these ranges that the pregnant reference ranges fit somewhere in between those of healthy people listed above. This is because of the increased demand that pregnancy places on your thyroid (4). 

Despite these, I have my own personal recommendations that I use when treating pregnant women. 

My personal recommendation:

  • First trimester: 0.1 to 0.5 mU/L
  • Second trimester: 0.2 to 1.0 mU/L
  • Third trimester: 0.2 to 1.0 mU/L

I discuss more about why I opt for tighter reference ranges below, but I at least wanted to introduce you to all of this information early. 

Download my Free Resources:

Foods to Avoid if you have Thyroid Problems: 

I've found that these 10 foods cause the most problems for thyroid patients. Learn which foods you should absolutely be avoiding if you have thyroid disease of any type. 

The Complete List of Thyroid Lab Tests:

This list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose thyroid hypothyroidism correctly!

Download more free resources on this page

Understanding Reference Ranges During Pregnancy

When we talk about reference ranges it's important that you understand what exactly they mean. 

A reference range is created by local lab testing companies. 

These numbers are supposed to represent the average numbers of all people in your local area. 

Lab companies create these ranges by taking information and lab results from thousands of people and then aggregate the data using statistical analysis to create the reference ranges (5). 

The goal of these ranges is to include 95% of the population within the ranges provided. 

This means that 2.5% of people tested fall below the reference range and 2.5% of people fall higher than the range provided. 

This idea is very important, especially when it comes to pregnancy and TSH testing. 

The reference ranges provided above based on trimester (the 0.1 to 2.5 for first trimester and so on) should only be used if your local lab company cannot calculate the TSH reference ranges for pregnant women who live local to you. 

Put another way:

You should NOT be using generic reference ranges when it comes to your TSH level during pregnancy because the TSH level can vary based on geographic location, ethnicity (6), and other factors such as your weight and metabolism. 

It's better to CREATE reference ranges based on your location than to use the generic reference range provided above. 

Unfortunately, not all lab tests do this for pregnant women because there simply isn't enough information available. 

It's not always clear if a woman is pregnant early on which can skew the data one way or the other. 

Because of this, I've created tighter reference ranges which take this factor into account. 

Healthy TSH in Pregnancy vs Outside of Pregnancy

The information I've referenced above is recommended based off of several studies. 

There is one big problem, though:

Most of the studies that we have on pregnant women include gathered information and data, not true double blind, placebo controlled tests (because it's not ethical to perform such studies on pregnant women). 

Furthermore, the information here is generalized, but we know that each person is unique and different. 

Normal TSH levels based off of individuals, age, ethnicity, and numerous other factors. 

thyroid treatment during pregnancy

So how can we create a "standard" range and then apply it to everyone?

In addition, we know that newer studies have shown that a healthy TSH (for those who are not pregnant) is probably less than 2.5 (7). 

And the studies I've referenced above indicate that you should keep the TSH less than 2.5 in the first trimester and with another breath also claim that normal TSH standard reference range from lab companies is as high as 4.5. 

So how can studies of healthy individuals show that a healthy TSH is less than 2.5 and then recommend that same level for pregnant women knowing that pregnancy places an increased demand on the thyroid?

How is it possible for some women to be completely "normal" with a TSH of 0.1 (which is within the reference range) ranging all the way up to 2.4?

This range is MASSIVE. 

It doesn't make a lot of sense, but this is the data that we are left with and we have to sort it out. 

My personal recommendation and feeling, based off of treating hundreds of people, is that a healthy and normal TSH is probably much closer to 1.0 in the nonpregnant state. 

With that in mind, I feel that using much tighter reference ranges for the TSH, especially during pregnancy, is warranted. 

You can find these tighter reference ranges below for the TSH:

  • First trimester: 0.1 - 0.5 mU/L
  • Second trimester: 0.2 - 1.0 mU/L
  • Third trimester: 0.2 - 1.0 mU/L

Why do I make these recommendations?

Because the risk of keeping the TSH in the low range is minimal and it outweighs the potentially negative effects of low birth weight and a low IQ in your child. 

Using these tighter reference ranges may result in slightly more patients who experience thyroid medication-related side effects, but it also dramatically reduces the risk of negative consequences to the baby. 

In my opinion, this is a trade-off worth making. 

If you are a woman who tends to be more sensitive to medications and you are someone who experiences heart palpitations with thyroid medication then you can aim for closer to the 0.5 range. 

If you are a woman who struggles with hypothyroid symptoms (hair loss, constipation, fatigue, weight gain) then you probably want to aim for the lower end of that range. 

The logic behind the tighter range is that we are staying within the "normal" reference range provided by the clinical studies (so we are not breaking the rules) but we are staying in the top 70-99% of that reference range. 

What Does Your TSH Mean?

We've been talking a lot about the TSH so far but I haven't really explained what it is and why it is important. 

The TSH stands for Thyroid Stimulating Hormone and it is one of the lab tests used to assess thyroid function in both pregnant and non-pregnant women. 

Your body produces TSH to stimulate the thyroid gland to produce thyroid hormone. 

It sounds simple to understand, and it is, but it's a little bit counterintuitive. 

A low TSH is usually an indication of hyperthyroidism while a high TSH is usually indicative of hypothyroidism. 

In pregnancy, a high TSH is an indication that your body is not producing enough thyroid hormone which means you may need to use thyroid medication. 

As you take thyroid medication your TSH will begin to lower. 

So, if you become pregnant and find that your TSH is 5.0 that is an indication that you need to take thyroid medication to help supplement the hormone that your body is producing. 

As you take thyroid medication your TSH will fall to a lower level. 

Doctors use the TSH to help determine how much thyroid medication you may need. 

Following the example illustrated above it may look something like this:

  • You find out you're pregnant and find out your TSH is 5.0. 
  • Your doctor starts you on 50mcg of levothyroxine thyroid medication and your TSH lowers to 2.6. 
  • 2.6 is outside of the recommended range of 0.1 to 2.5 which means your thyroid is not optimized. 
  • Your doctor then increases your dose to 75mcg of levothyroxine and rechecks your TSH. 
  • Your follow up TSH is now 1.8 which is within that normal range.
  • *Note: I recommend further changes to your medication at this point, especially if you are symptomatic (weight gain, hair loss, constipation, dry skin, etc.), but you technically are "normal" by testing standards.  

This is generally how the TSH is used both in pregnancy and outside of it. 

Even though we are discussing the TSH in this article, it's still important to know that they are other tests that can also be used (and should also be used) to test your thyroid. 

These other tests include the free thyroid hormones free T3 and free T4

These tests should almost always be ordered with your TSH because it puts the TSH into context that you simply don't have if you only look at the TSH. 

It's certainly possible for your TSH to be 1.8 but your free T4 or free T3 to be low. 

And in this situation, you would want to continue treatment to optimize your free thyroid hormones. 

Thyroid Medications During Pregnancy

If you have a high TSH (or known hypothyroidism prior to becoming pregnant) then there are special changes that you must make once you know you are pregnant. 

These changes include increasing your dose of thyroid medication immediately upon finding out or suspecting you are pregnant. 


Because your child, especially during the early stages of development, is reliant upon your thyroid hormone until it can produce its own thyroid hormone. 

During the first trimester, your child will be relying upon your thyroid gland for its thyroid hormone. 

And, if you are taking thyroid medication your ability to produce thyroid hormone is limited. 

This is why most doctors recommend that you increase your dose of thyroid medication anywhere from 20 to 50% (and even all the way up to doubling your existing dose). 

In fact, this recommendation applies even if you miss or skip a period and suspect you might be pregnant. 

The most critical time in development often occurs before you even know that you are pregnant. 

Because of this, it's very important that you pay attention to your body and try to find out if you are pregnant as early as possible. 

Most physicians recommend the use of T4 only thyroid medications such as Synthroid and levothyroxine during pregnancy. 

But does that mean you can't use other thyroid medications?

Not at all. 

In fact, many women use other thyroid medications such as NDT and cytomel/liothyronine safely during pregnancy. 

Instead of focusing on which medication you use, you should focus on your thyroid lab tests (TSH, free t3, and free T4) and how you are feeling. 

If you are experiencing the symptoms of hypothyroidism, even with a TSH of 2.4, it may be time to adjust your dose slightly higher to compensate. 

You can discuss these options with your Doctor. 


My goal here is to simply provide you with information so that you can become knowledgable on the subject and make the best choices for both you and your baby. 


TSH levels vary based on a number of factors including your age, weight, ethnicity, and metabolism. 

It's important to take all of these factors into account when you are pregnant to ensure that your child gets sufficient thyroid hormone. 

You can take into account these variables by looking at special calculated pregnant ranges based on your geographic location (which should be provided by the lab company which runs your tests). 

If these tests are not available then you can use the standard reference ranges provided above. 

If you are concerned about the long-term health of your child and want to provide them with the best possible thyroid environment, then I would recommend you look at my tighter reference ranges. 

Now I want to hear from you:

Are you currently pregnant? 

What is your TSH?

Are you taking thyroid medication?

Do you feel that your medication is optimized?

Leave your questions or comments below! 

References (Click to Expand)

TSH levels during pregnancy

Dr. Westin Childs

About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 45,000+ people have used them over the last 4.5 years. You can read more about my own personal health journey and why I am so passionate about what I do here.

22 thoughts on “TSH Levels During Pregnancy: What’s Healthy & Normal?”

  1. Hi,
    I’m planning pregnancy. I have hashimoto’s and I have reverse T3 syndrome. I’m 35, already have a 10 yr old son. My thyroid problems started after giving birth.
    Currently I do not take any medications and I don’t feel any symptoms, but I have to lower my TSH (around 4-5, just waiting for my test results). Most doctors do not know anything about reverse T3. When I took only T4, I was feeling very bad, had a horrible hairloss, was weak, etc. Because of that my doctor doubled my dose and everthing got even worse.
    After that, I switched to T3 only on my own, which worked fine than I couldn’t get it anymore. So I’m not taking any medinices in the last 4 years. What’s your opinion? I know I need to take some thyroid medications especially during pregnancy, but I’m really afraid of T4 as it caused a lot of problems earlier.
    Are you taking online patients, so I could send over my results and have a discussion about this?

  2. Hi Doctor, I’m 6 weeks pregnant and my TSH levels are 3.1
    They were 1.8 before I got pregnant.
    I was given some medications today but is it possible that this have already affected my baby? Please let me know your opinion. Thanks

    • Hi Patricia,

      The answer is always potentially yes, but you will probably never know for certain. That’s why it’s best to start before you get pregnant (as stated in the article).

  3. I’m so thankful for all your free articles and podcasts. I just found out I’m pregnant and was following your plan with a huge success of victoza, LDN, cytomel and testosterone. My provider immediately recommended I stop everything including cytomel because they are worried about suppressed TSH. Goes against everything you stated above about the thyroid. I don’t convert FT4 to T3 and cytomel has been a game changer. Would you recommend a combo of T3 and maybe naturethroid?

    • Hi Kay,

      I can’t make personal recommendations, but it’s not a good idea to continue the other medications during pregnancy. Thyroid hormone, however, can and should be continued. What medications you choose to use depend on a number of factors. It’s not about what medicines you use but how they are dosed and what your body needs. For instance, Cytomel or NDT aren’t necessarily bad, but they can be if they are overdosed/underdosed during pregnancy. Most doctors aren’t comfortable using medications with T3 in them so they typically try to switch women to T4 only medications during pregnancy.

  4. Prior to getting pregnant, I was on 90 mg Armour, and my numbers were:
    TSH 0.162
    FT4 0.9
    T3 3.3
    Although my hair was falling out, I wasn’t overly fatigued, and my doc wasn’t worried, so these numbers didn’t concern me too much.
    As soon as I found out I was pregnant (around week 4), I contacted my docs. My endo switched me to 150 mcg levothyroxine. (My functional doc wanted me to continue with Armour 3 x a week – in addition to the levo – but the endo disagreed).

    At just about week 5, I had labs. The results were:
    TSH 2.610
    FT4 1.1
    T3 2.0

    Obviously, I had only been on the levothyroxine for a few days when I had these labs done, and I know that it takes time. Still, it seems like time is of the essence, and it makes me anxious that these are not optimal. I have contacted my doc to make sure that he still feels confident about the dosing.

    How often should labs be repeated in the first trimester? It seems like it should be important to get the number optimized as quickly as possible.

    Also, are the standard ranges for FT4 and T3 the same during pregnancy as they are normally? I haven’t seen different ranges noted for pregnancy.

    Appreciate your insight and your posts!

  5. Hello Doctor,

    My wife is passing through 3rd trimester of pregnancy.

    In recent test, she has report as below.

    T3 : 2.27
    T4 : 10.43
    TSH: 2.6

    She takes dosage of Thyroxine sodium tablets IP (25 mcg).

    Please recommend if she should increase dosage.

  6. My thyroid levels have been tested due to heart palpitations in pregnancy. I am 21 weeks and 5 days, Caucasian, 5ft 2 and was 124lbs pre pregnancy I am now around 133lbs. My TSH levels originally came out at 0.286mlU/L so they were retested with the T4 free levels thinking I may have developed hyperthyroidism. They have now come back at TSH 0.38 mlU/L and T4 free 0.8ng/dL. The doctor has told me my TSH is still low and my T4 is on the lower side of normal. As I am in the process of switching doctors she will leave it up to them to decide if they want to treat me. I am so confused by what this means? Is my baby at risk?

    • Hi Georgia,

      Not necessarily but it could be that your baby may be at risk. If it were me, I would recommend that you just closely follow both the growth of the baby and your own health. As long as your baby is growing and as long as your health is fine then you should be able to avoid thyroid blocking medication.

  7. Hi Dr. Westin Childs,

    My wife just found out she has some type of hypothyroidism and she is about 5 or 6 weeks pregnant. Her TSH is 8.04. She is 34 and she had a healthy baby girl 1 and a half years ago where there were no signs of thyroid issues. She is now taking Synthroid 0.05mg and Levothyroxine na, 0.05mg. It is in one pill.

    I am concerned that the medication is not being optimized because according to the doctor at the walk-in clinic it is a low dose but her TSH is quite high at 8.04. Do you think she should revisit with a doctor taking a higher dose since her TSH is quite high?

    Will it be beneficial to get new lab results after 2 weeks or how soon should she get bloodwork again to monitor it and get her TSH lower?

    Thanks very much,

    • Hi Dave,

      You definitely want the TSH lower than 2.5 (at least) during the first trimester of pregnancy. So it would be a good idea to check her dose in a couple of weeks to see where that TSH is. A low TSH during the first trimester of pregnancy is associated with a number of issues for the child so definitely stay on top of it.

    • Hello,

      I just found out I am pregnant last week (Saturday). I had my tsh checked on Monday. It came back .4

      A little history about me. I had my thyroid removed 13 yrs ago when I was 22, due to thyroid papillary cancer.
      I was pregnant last year but had a miscarriage around week 7-8.

      This time, Before pregnancy, my last tsh result was .4.
      My doctor reduced my dosage to 125mcg everyday in July.
      Now she wants me to take 125mcg 6 days a week and two pills on the seventh day ( so 250mcg).
      Does this seem like an appropriate dosage to change to? I am extremely concerned that I will have another miscarriage.

  8. Thanks for answering Dr. Westin Childs. I am seeing a lot of information with regards to waiting to do bloodwork after 4 weeks because it is difficult see any results from the medication until then. Now 4 weeks seems like a long time since we only have probably about 6 weeks left of the first trimester! Is there no better way to test TSH levels and monitor how high of a dose is required? It seems like bloodwork should be done more often. What is your take on how often bloodwork should be done?

    Thanks a lot,

  9. Hello Dr. Westin, I’m 31 weeks pregnant and just recently got blood work done as well as my thyroid, my TSH was showing in the normal range (.97 and .91). My Free T3 was showing elevated (9.2 and 8.5) when the range is 2.2-4.2. The second blood draw showed T3 was elevated at 3.21 and T4 >24.9. The endocrinologist was confused as I am not showing any symptoms of hyperthyroidism, and was wanting to do an MRI on my pituitary, as well as an ultrasound on my thyroid. I prefer to not do either of these as I do not do ultrasounds during my pregnancies (I have homebirths).

    • Hi Traci,

      Most endocrinologists live in a weird world where they believe that the TSH is the sole marker for thyroid status in the body so they can’t fathom a reality where the TSH can be low while the patient isn’t hyperthyroid. You can see transient changes like this during pregnancy and it isn’t necessarily a problem (though it could be).

  10. Hello, I found out I am 8 weeks pregnant. I have Hashimoto’s autoimmune. What I found weird is when I tested my Tgab and TPO, my TPO dramatically decreased to 32 and my tgab decreased to 344.5 but is still considered high. Not sure if that is something to worry about as most doctors worry about TPO.

    My TSH was 0.95, free t3 3.4, and Free t4 1.42. When I followed your directions with comparing to my lab ranges based on the percentile, the free t4 and free t3 were off by a couple of points being a little low. Nothing dramatic. Any advice.

    • Hi Kim,

      They are at the bottom of the page where it says “Reference (click to expand)” 🙂 In addition, you can also just click on the links where the numbers indicate the reference to be taken directly to that reference.

  11. I’m currently 16 weeks pregnant at 32. I was diagnosed with Hashimoto’s when I was 24 (TPO around 680) and I’ve been symptomatic of it since I was 7.

    Prior to pregnancy my numbers generally were optimal on a low dose of NDT and T3 only, TSH was suppressed at under the range, but Free T3 was top 25% of the range for the last 5 years. This left me with few symptoms and feeling decent. It also dropped my TPO from that higher number to the 60s. I do have adrenal and iron problems as well, hence only a low dose of NDT because I will otherwise convert T4 into Reverse T3 almost exclusively.

    Now that I’m pregnant, all the OBGYN seems to want to focus on is TSH like it’s the end all be all and they cannot possibly seem to comprehend that TSH can be suppressed when optimal on a T3 containing medication (inserts literally say these medications do this).

    I keep a steady watch of my thyroid levels and adjust accordingly though in spite of this, but it literally got me kicked out of my OBGYN’s office today because I refused to go off my meds and see if my TSH would go back up after a month or two like my doctor wanted. So I’m just going to go with a midwife, so I can skip the doom and gloom as well as the headache.

    I assume there’s just no possible way to change some of these doctor’s minds on TSH is there? They dogmatically follow it like they’ve been brainwashed.

    For reference too, every appointment my baby’s had a healthy heartbeat and was perfectly healthy on the 12 week ultrasound, right on target with growth, etc. For myself, other than high blood pressure at the last appointment, which was back to normal at home, I’ve been good, blood sugar’s good, blood pressure is generally good (I check it regularly), and all that.

  12. I am now 8weeks pregnant. And my doctor has started me on vaginal progesterone. Not taking it close to my thyroid medication levothyroxine. But will this cause my TSH to rise at all. And I feel like my doctor is not Raising my levothyroxine enough I had a TSH of 2.64 taking 100mcg and now she only raised it to 113mcg . I worried that it will not be enough and also being on the progesterone. Thank you

  13. Hi, I’m 8 weeks pregnant and just found my TSH is as high as 9.3. I had hashimoto’s. I wish I had read your article earlier. Now I’m just so concerned. Would my baby’s IQ be affected? How much levothyroxine should I take each day? And when should I test my TSH the next time?

    Thanks very much!


Leave a Comment

Item added to cart.
0 items - $0.00
Your Cart
Your cart is emptyReturn to Shop
Calculate Shipping