Thyroid UK
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Levothyroxine 25mcg pregnant

Hi im 14 weeks pregnant. Ive had underactive thyroid for 2 years now but just mild. Ive only ever been on 25mcg. I got bloods checked less than 2 weeks ago and my thyroid levels are still in range however 20 minutes or so after i take it i have a strange sensation in my chest and my hearts racing and i feel weak. ive only noticed this the past week or 2. Is this normal i really hate the feeling it put me off taking it this morning. Thanks

2 Replies

Welcome to the forum, Danid1989.

What were your thyroid results? NICE recommend the TSH of pregnant women should be in the low-normal range 0.4-2.0 with FT4 in the upper quadrant of range.

The baby will have developed his/her own thyroid gland by 12 weeks so won't be dependent on maternal hormone any longer but if you stop taking Levothyroxine it increases your risk of post-partum thyroiditis.

It's possibly low blood sugar causing the symptoms. Perhaps you could have breakfast and take Levothyroxine 2 hours afterwards and see whether symptoms improve.


Im not sure she said 1.4 something. She said it was within range. Yea i will try that and see. Thanks alot x


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