It may take a few weeks for Synthroid to begin working, and you may not see any change in your symptoms until then. Some foods also can affect how Synthroid is absorbed, such as soybean flour, cotton seed meal, and dietary fiber. If you are taking Synthroid, your doctor will perform periodic blood tests to determine whether you are getting the right amount. While taking Synthroid, your doctor will perform periodic blood tests to determine whether you are getting the right amount. You need to take Synthroid because of a thyroid hormone deficiency, Synthroid can also be used to treat or prevent goiter enlarged thyroid gland, which can be caused by hormone imbalances, radiation treatment, surgery, or cancer. You take Synthroid with an appetite-suppressant medication.
