When should FT4 be retested?

The question of when to retest FT4 (free thyroxine) cannot be answered from the provided context, as none of the articles or Q&A entries address thyroid diagnostics. In general medical practice, FT4 is typically rechecked 6–8 weeks after a dose change of thyroid hormones (e.g., levothyroxine) or after starting antithyroid therapy. For stable patients, monitoring every 6–12 months is common. During pregnancy, weight changes, or new symptoms (e.g., fatigue, palpitations), earlier testing may be warranted. Interpretation should always be done by a physician, as reference ranges vary by lab and individual factors (e.g., medications, kidney function) affect results. Without a specific clinical scenario, a blanket recommendation is not evidence-based. The evidence level is rated 'unclear' because the context provides no relevant studies or guidelines on FT4 retesting intervals.