Thyroid UK
87,777 members102,472 posts

Optimal ranges in pregnancy?


I've just had a long long awaited positive pregnancy test after our second round of IVF. I was found to be borderline hypo last year (TSH 4.9) and have been on 75mg levothyroxine since January which had brought my TSH within normal range.

I've now been told by the hospital to double my Levo dose twice a week due to the pregnancy so I'm taking 150mg on a Wednesday and a Saturday. I've been doing this since last week (am now just 3 weeks pregnant) and feel ok but perhaps ever so slightly hyper, which is fine by me but I want to make sure I do everything I can to reduce the risk of miscarriage or harming the growing embryo. I know the optimum range for TSH in pregnancy is 0.1 to 2.5 but does anyone know what level becomes harmful I.e means you are having too much thyroxine?

Also, what are the optimal ranges for T4 in pregnancy? And again the harmful ranges?

I presume I should get my blood tests done avoiding Wednesday and Saturday for the fairest picture?

My hospital are leaving it to the doctors to monitor me and they aren't very proactive and it's difficult to get more than a TSH so I'm thinking of going to a private endocrinologist to put my mind at ease during these crucial few weeks. Could anyone recommend a specialist in the West Midlands who they have found good to work with?

Apologies for the long post. Any advice gratefully received x

6 Replies



I'm not aware that low TSH is a problem. It is high TSH which should be avoided.

1st trimester 0.4-2.5

2nd trimester 0.4-3.0

3rd trimester 0.4-3.5

You can order TSH, FT4 and FT3 via Blue Horizon Thyroid Plus 6

Email for a list of member recommended endocrinologists.

1 like

Thanks Clutter! this is the article that made me worry. I'm probably over-researching as usual!



Excess thyroid hormone means FT4 and/or FT3 are over range ie hyperthyroid or over medicated hypothyroid women. You need adequate thyroid replacement but no one is suggesting you should be over medicated.

1 like

Thanks, no I didn't think that. Sounds like I need to get a full thyroid panel every few weeks if possible. Thanks again for your help


I've just had my latest test results back and TSH is still 3.81 so I can't be hyper and now worried i'm still hypo. However this was only two days after my first doubled dose so hopefully this will come down soon. I also just read that oestrogen can affect Levo and I've not been taking my oestrogen tablets 4 hours apart from her Levo so I'll do that in case it's preventing absorption.


Hi Cmat

Firstly congratulations!!! Exciting news!

To put your mind at ease, currently my TSH is <0.01 (basically non detectable) (T3 T4 normal) at the moment after my Graves relapse and my endo said it's ok for me to get pregnant!

I have also learnt that in the first trimester, it is important to keep under 2.5 due to the high demand of T3 T4 while pregnant, so don't worry too much about TSH being low as long as they are within normal range and T3 T4 are normal that is my take.

Good luck with the specialist. Wish you a safe and healthy 9 months.

Littlegrass xx

1 like

You may also like...