most cold medications are safe to use with thyroid hormone. the only ones that i would caution you about are the decongestants like pseudoephedrine and phenylephrine. these could increase your heart rate and cause you to feel like you have too much thyroid hormone in your body. i suggest you talk to you pharmacist before taking any over-the-counter cold medicine so he/she can make certain it does not interact with your medication or your condition.
can i use over-the-counter cold and flu medicines if i also take medication for a low thyroid?