I’m in a similar situation so I have been doing a ton of research on this (I have had hypothyroidism for 20 years, and my doctors don’t seem to be as proactive about addressing this during my pregnancy as I’d like. I’m now 6 weeks along). This article is a really good summary of the science on this topic: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3163038/
The medical recommendation for anyone with pre-existing hypothyroidism is to immediately increase your dosage by 25-30% as soon as you know you’re pregnant. I wish a doctor had told me this! I didn’t know this until now - at 6 weeks - and am upset that my doctors dropped the ball (I did IVF, so the fertility doctor should have told me about this when we did the embryo transfer)
I was told to increase as soon as I got pregnant but after bloods were taken it was found that I didn't have to until the second trimester. I'm now on 125mcg (24 weeks)
I was told to increase straight away. I’m now on 200mcg and levels are still 25 🙄 my levels started off at 80 😒 nothing is working so no idea what happens next currently 15 weeks x
I was advised to increase by 25mcg daily immediately. The increased dose shouldn’t really have an effect on your blood test in 2 days as takes a while to see the effect of levothyroxine in your thyroid levels