Hello – At 4 weeks out, you should be able to get a good read on the effect of the dosage change, so I would ask your doctor if you can get labs done more quickly.
I haven’t seen any specific studies on thyroid hormone replacement dosage and breastfeeding, but if you have any concerns, your doc should be able to test your baby’s thyroid function just as a precaution.
Wishing you all the best!
Kimberly
