*This statement summarizes the third USPSTF recommendations for screening for chlamydial infection and the supporting scientific evidence, and it updates the 1995 recommendations contained in the Guide to Clinical Preventive Services, second edition (1).
Older adults may be more sensitive to the side effects of this drug, especially fast/pounding/irregular heartbeat. Current information shows that this drug may be used during pregnancy. Tell your doctor if you are pregnant because your dose may need to be adjusted. Levothyroxine passes into breast milk but is unlikely to harm a nursing infant.
Common Side Effects of Synthroid. Instances of Synthroid side effects are not particularly common, typically occurring in less than 1 percent of users. The most common of these include change in appetite, diarrhea, headache, leg cramps, and shortness of breath, vomiting or weight loss.ynthroid Side Effects. Synthroid is a synthetic hormone that is used to treat hypothyroidism by replacing the hormones that are not being produced due to a malfunctioning thyroid gland.