 [ Symptoms ] can benadryl have a side effect when combined with suboxone [ Disease ] the short answer is it should not levothyroxine is a thyroid hormone replacement doctors prescribe this medicine when a person is thyroid gland is not making enough thyroid hormone on its own this condition is called  hypothyroidism  or low thyroid  hypothyroidism can cause a person to gain weight however taking levothyroxine might actually stop weight gain caused by low thyroid a dosage of 88mg is common for levothyroxine if you have any questions about this medication or why you are taking it you should ask your doctor wishing you well