Low TSH and slightly raised FT4 in early pregnancy on levothyroxine

[Ara26]

Hi everyone, I’m looking for some advice/reassurance about my thyroid levels in early pregnancy.

I’m currently 5 weeks pregnant following a frozen embryo transfer.
I’ve been on Levo since Jan 2026 as my tsh was 3.9 and we needed it to be under 2.5 to proceed with my transfer. My tsh was 2.19 in May so went ahead with transfer in July.

My fertility consultant advised she didn’t think it’s worth testing my thyroid levels at this stage but I couldn’t stop thinking about it and went to a private clinic today.
My results are:

• TSH 0.219 — low
• FT4 22.4 pmol/L — just above upper limit
• FT3 5.49 — normal
• Current dose: Levothyroxine 25 mcg/50 mcg alternating

I’ve had a previous miscarriage, so I’m understandably very anxious about my thyroid levels and whether my medication dose is now too high, or whether a low TSH could affect my pregnancy.

I’ve self-referred to my maternity unit today, but I’ve found my GP unfortunately hasn’t been very helpful when it comes to managing my thyroid

Has anyone had a TSH around 0.2 in early pregnancy while taking levothyroxine? What was your free T4, and did your dose need to be changed? Were you referred to antenatal endocrinology or monitored more closely?

I’m so scared.

Completely understand your anxiety! I’ve just had a failed cycle and previously miscarried three times ( before being diagnosed with under active)

My results were similar to this and i was advised to alter the meds and take it every other day.
You should be under the consultant in pregnancy for IVF and endocine, when seen at booking they should repeat the test , in second and third trimester too, good luck xx

Thank you for replying! So sorry to hear about your failed transfer and miscarriages. What dose were you taking every other day please? And was this your GP that advised the change? xx

i can’t remember what dose i was on but sometimes when you take too much that’s why the tsh is lower. I think i was on 50 and when i found out increased it to 75, i was told to get selenium ( from holland and barrett) and that really helps with the levels too!

When I was pregnant around 10 years ago, the advice was to increase the dose of thyroxine by 25-50mcg immediately, as demand can increase quite rapidly in early pregnancy, and to monitor every 4 weeks during the first trimester.

My TSH was slightly below range before I got pregnant, and it dropped further, to around 0.1 I think, after increasing.

How do you actually feel? You're not that far out of range - FT4 is only slightly elevated and FT3, which is the active hormone, is normal. I had no symptoms of being over medicated and chose to stick with my dose and monitor every 4 weeks during the first trimester, as I felt that being slightly over medicated in the short term was preferable to the risk of being under medicated.

I did then drop the dose slightly at 16 weeks, as my TSH was consistently low in every test, and by that time the baby's thyroid should be starting to function and will be less reliant on maternal hormone levels.

Spoke to my GP today who suggested I take 25mcg daily instead of alternating 25/50mcg. I hope this is the right call. I have a repeat blood test in 5 weeks.

Just spoke to my fertility consultant who told me to stick with my 25/50mcg dosing. She was worried I would be under-medicating by decreasing to 25mcg a day. So will stick to the alternating dose.

Why is managing thyroid so tricky… pre treatment and pre planning for pregnancy I never knew the importance of the thyroid!!

I think that's sensible - you're on quite a low dose anyway, and thyroid hormone demand is known to increase in early pregnancy. Hope all goes well!

Thank you! I do feel better about this decision too!

I have no thyroid so rely solely on medication for my levels. So hopefully this will reassure you, I increase my dose immediately on finding out, this often causes me to be slightly hyper for a few weeks but it ultimately ends up at a better level after that. Just make sure to go for repeat bloods every 28 days as it can swing around quite a lot. I agree with you sticking at the dose you were on. I sometimes drop to 0.2 anyway when not pregnant and actually feel a lot better in myself at that level lol

Thank you, this has actually reassured me. I have moments when I catch myself spiralling but reading other people’s experiences is so helpful!

Please can I ask what your T4 levels tend to be when your TSH drops to around 0.2?

@Ara26so last time TSH was 0.21 was March (so about 3/4 months pregnant and my T4 was 123 mmol/L

Also to add to the last my TSH at my next test in June was 1.19

Thank you! The results above were from a private clinic. I have a nhs blood test scheduled for 5 weeks, would anyone know if the antenatal team accept private blood tests results? Not sure whether I should move my NHS test up sooner so that I can have my tests on the NHS system?

Ideally you want them 4 weeks apart, I wouldn’t know about private testing and if nhs accepts though as mine have all been through nhs