Thyroid UK
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Pregnant with hashimotos

Hi All,

I was wondering if anyone could enlighten me on the following please.

I have hashimotos but a working thyroid, my Dr on the advice of my specialist has upped my thyroxine to 100 mcg, previously on 25 mcg. I was wondering when should my bloods be re checked as I'm worried the increase could send me overactive, I've now been on this dosage for 4 weeks.

Thank you :-)

10 Replies

Welcome to our forum Tina2788

100mcg is not a high dose but thyroid antibodies attack your gland until you become hypothyroid.

It is usual to be prescribed thyroid hormones if patient has antibodies. It is an Autoimmune Thyroid Disease called hashimoto's. As you are pregnant I'd go along with the Endo.

Hashimotos is the commonest form of hypothyroidism.

You should have a blood test every six to eight weeks, fasting (you can drink water). Also allow a gap of 24 hours between last dose of levothyroxine and the test and take afterwards.

Levothyroxine should be taken on an empty stomach with one full glass of water and wait about an hour before eating. Food interferes with the uptake. Some prefer a nightime dose. In that case you should last have eaten about 3 hours previously. If getting a test next a.m. miss night dose and take after test and at night as usual.

Always get a print-out of your results with the ranges and post if you have a query.

GP should also test B12, Vit D, iron, ferritin and folate if you've note already had them done.

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Dose is usually raised by 25-50mcg when pregnancy is confirmed so your TSH may have been a bit high as your specialist suggested increasing to 100mcg.

It's usual to check bloods 6 weeks after adjusting dose.


Hi Clutter,

Thank you and thank you for reply, my bloods were tested before my dosage increase and although they didn't give me my actually results supposedly my thyroid was coping and in range.

I was under Salford hospital at one point and they were very adamant not to get pregnant, which I think has increased my stress and anxiety and I don't feel like the Drs are very forthcoming with what should be happening next!

I'm so glad I found this forum at least your knowledge can support and help people like myself, so thank you for taking the time to reply.



TSH in range could be anywhere between 0.27 and 5 or 6. It is recommended that the range for women planning conception and newly pregnant should be 0.4 - 2.5 as TSH higher than that can make conception difficult and also increases the risks of miscarriage.


Thank you, I think my best bet is to go get my bloods done and find out what they actually are.



4 weeks is a bit early. Wait until 6 weeks.

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Congratulations on your pregnancy!

I am currently on my 3rd pregnancy with an underactive thyroid.

Check out the website, It has lots of great articles, (I have included some thyroid/pregnancy articles at the bottom) Buy the book she wrote on pregnancy-it’s amazing! “Your Healthy Pregnancy with Thyroid Disease”, by Dana Trentini & Mary Shoman.

You should have blood tests every 4weeks until 20weeks. The results of these tests, will likely show that you need further increases. (Don’t increase without the blood tests to tell you how much you need.) Your blood tests need to include T3 results. If your GP won’t do this, get private testing done through “Blue Horizon.” As always, get copies of all your blood tests, and post on here for advice. Do not accept your GP telling you that you are “normal” or “within range” as very few of them know what is healthy for pregnancy. At 20 wks, the demands usually plateau and you will need tests/increases less often. (The book tells you how often.)

The book I mentioned above, gives this advice about the TSH levels you need to have to have a healthy pregnancy. This is really helpful to take to your doctor.

First trimester: less than 2.5 with a range of 0.1-2.5

Second trimester: 0.2-3.0

Third trimester: 0.3-3.0.

TSH should be monitored every 4 weeks during the first 20 weeks of gestation, then once again between 26 and 32 weeks

Keep an eye on your B12 levels, as pregnancy places a high demand on these and people with an underactive thyroid are usually deficient to begin with. (You can’t overdose on B12, anything you don’t need you will pee out. A bit of a waste of money, but not dangerous!)

Some articles, you may like to read:

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease during Pregnancy and the Postpartum

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Thank you for all the information! Just to double check that once pregnancy is positive one should do blood tests right away and then every 4 weeks under NHS guidelines till week 20? Thank you, total newbie here 😊!


Increase dose, phone your GP to make an appointment, book blood tests through them asap. (Fast for 12hrs before blood test & take your your needs after your blood test. Make sure they test for TSH, t4 & t3. If they won't do T3, get it done privately.) yes, do blood tests every 4 wks until 20wks, then the tests can be done less than that. (check the book) check the gp has referred you to a consultant who should take over your care. This should happen asap, but often doesn't. (I didn't see a consultant till 16wks this pregnancy.)


Thank you so much for the information. I'm trying to read up as much as I can so I'm fully aware.

I've never had an under active thyroid result it's been a waiting game since the diagnosis of Hashimotos which was my concern of raising my thyroxine by so much (although this was done on the advice of my consultant).


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