Hi,
Synthroid contains the active drug levothyroxine which is used to treat hypothyroidism and certain type of thyroid cancer. A very serious
allergic reaction to Synthroid is rare. However, get
medical help right away if you notice any symptoms of a serious allergic reactions, including- rash, itching, swelling of face, tongue or throat,
severe dizziness, trouble breathing etc.
Again, high TSH levels can mean your thyroid is not making enough thyroid hormones, a condition called hypothyroidism. Hypothyroidism may cause low blood pressure and decreased heart rate leading to
lightheadedness, weakness, dizziness, lethargy and chills. So, do repeat your
thyroid function tests and adjust your Synthroid dose according to your test results.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Zubayer Alam, General And Family Physician