I was diagnosed with hypothyroidism, and have been taking Synthroid for a few years. However, while on the Synthroid, I have had on and off heart palpitations. Every time I go for my blood test (every six months), the doctor tells me that everything looks good and keeps me on the same dosage of Synthroid. However, recently the palpitations have gotten worse, to the point where I'm dizzy and light headed. I almost made the decision to go the ER tonight as a precaution, but ultimately decided against it. I just took my blood pressure and pulse rate, and both are normal, not high, but my heart is still beating irregularly. Could this just be related to my hypothyroidism and Synthroid medication, or could this be something else? Thanks in advance.