id contains both Thyro
id hormones, T3 and T4. T4 is the "storage" form of the Thyro
id hormones, and it is very slow acting. It takes weeks to build in your blood and raise your levels. T3 (the "active" form of the Thyro
id hormones), on the other hand, is very fast acting, and it can take some getting used to.
id meds can cause reactions initially, especially if you are over 50, have been hypo for a while or have a heart arrhythmia.