What is the conversion rate from oral to intravenous Levothyroxine?

The conversion rate from oral to intravenous Levothyroxine is indeed that the intravenous dose is typically 50% of the oral dose. This adjustment is necessary due to the differences in bioavailability between the two routes of administration. When Levothyroxine is taken orally, it undergoes first-pass metabolism in the liver, which can reduce the amount that reaches systemic circulation. In contrast, when administered intravenously, the medication bypasses this initial metabolism, resulting in a more potent effect per unit dose. Thus, using half the oral dose for intravenous administration ensures that patients receive an equivalent effect without risking toxicity or excessive hormone levels.