If you are wondering can levothyroxine cause weight gain, the medication itself usually works in the opposite direction by correcting the low-thyroid state that can contribute to weight gain. If weight keeps rising after treatment starts, the next step is to investigate dose, absorption, timing, and other possible causes. Levothyroxine is prescribed to replace thyroid hormone when the body is not making enough of it. Because untreated hypothyroidism can slow metabolism, increase fluid retention, and…