The Levothyroxine PO to IV Dose Conversion calculator adjusts the levothyroxine dose when transitioning from oral to intravenous administration. The IV dose is typically 70-80% or less of the oral dose due to higher bioavailability.
Reference
Jeffrey R Garber, Rhoda H Cobin, Hossein Gharib et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012 Nov-Dec;18(6):988-1028.
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