Thyroid UK
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Levothyroxine and FET-IVF cycles


Before I started a IVF-COH cycle in April last year, my tsh read 6.33(2nd gen), t3&t4 normal. I was put on levo 25mcg every other day. The cycle failed and I took myself off levo coz the thyroid dr gave me the option of taking or leaving the meds at 6.33.

In Dec last year,my tsh read 16.1(3rd gen),ft3 normal&ft4 a little low at 0.64(0.93-? range).(I read COH cycles are extremely stressful for thyroid). I was put on 25mcg daily.

In Mar this year, my tsh read 3.22(3rd gen),ft3&4 normal. Continued same dose.I followed an IVF-FET cycle in April which failed.

Last month, same dose, my tsh(2nd gen) tested at 3.194.A new endo increased my dose to 37.5mcg.

Yesterday(a mth later), I tested at 2.27(3rd gen). I am planning on starting another IVF-FET in a few days, and I am concerned its not enough esp.with all the estrogen I will be taking for the cycle.

I would like your opinion about the following:

From start of cycle or even from now, is it ok if I increased my dose to 50mcg twice or thrice a week, and rest same dose(37.5)?

will implementing increased dose on commencement of cycle a good idea? I go for transfer 2 weeks later,so wish for levels to be stabilized by then.Is 2 weeks enough for levels to stabilize?

Are readings higher on 3rd gen tsh tests than 2nd gen ones?

My ivf dr useless at this, my endo im yet to see, I would really like some opinions since I am a little skeptical about the endo as well.


4 Replies


It can be very difficult to conceive when TSH is >3.0 and risk of miscarriage is considerably increased.

I would increase dose to 50mcg daily. Women planning conception should have TSH in the low-normal range 0.4 - 2.5. Levothyroxine dose should be increased by 25-50mcg when pregnancy is confirmed to ensure good foetal development.

Guideline from: Management of primary hypothyroidism: statement by the British Thyroid Association Executive Committee

13. The serum TSH reference range in pregnancy is 0·4–2·5 mU/l in the first trimester and 0·4–3·0 mU/l in the second and third trimesters or should be based on the trimester-specific reference range for the population if available. These reference ranges should be achieved where possible with appropriate doses of L-T4 preconception and most importantly in the first trimester (1/++0). L-T4/L-T3 combination therapy is not recommended in pregnancy (1/+00).

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Thanks for the reply.

After being on 37.5mcg daily for a month, 2 days ago, my TSH (3rd gen) came back at 2.27 (ref 0.27-4.2). 2.27 is within the reference range for women planning conception, but Im concerned with all the estrogen I will be taking for the FET cycle(which im set to start in possibly couple of days) that 2.27 is still a little high.

#Will starting the increase at about the same time as the fet cycle cause some issue? 2 weeks after starting cycle,I go for embryo transfer, so would tsh levels have stabilized by then or would it require longer to stabilize?

#what is the difference between TSH test and TSH 3rd generation test?

#If my TSH was 2 for example in a regular tsh test, would it be like 4 on a 3rd gen tsh test,because of increased sensitivity?




0.4 - 2.5 is the recommended range for women planning conception and in the first trimester of pregnancy. 2 weeks may just be long enough for TSH to dropped on the increased dose but I have no idea how it will be affected by oestrogen or your IVF treatment.

TSH 3rd generation is a regular TSH test. It is the latest version TSH test and will be more sensitive than previous generations. I believe itt measures TSH to lower levels, say 0.0001, rather than <0.01 on previous generations.

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Thanks. You have been very helpful


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