After starting Levothyroxine for hypothyroidism, when should TSH be rechecked?

After starting Levothyroxine for hypothyroidism, when should TSH be rechecked?

• A. Within 24-48 hours
• B. In 6 months
• C. In 6-8 weeks
• D. In 1 year

Answer: (C)

After starting levothyroxine or changing its dose, TSH should be checked about 6–8 weeks later. This window matches how long it takes for the body's thyroid axis to reach a new steady state after a dose change, so TSH accurately reflects whether the replacement dose is appropriate. Checking sooner—like within 24–48 hours—won’t show the full effect, since TSH lags behind changes in thyroid hormone levels. Waiting much longer (months to a year) delays optimization and can keep patients hypo- or hyperthyroid longer than necessary. If the TSH is not in range at 6–8 weeks, adjust the dose and recheck in another 6–8 weeks. Once a stable dose and TSH are achieved, monitoring typically occurs every 6–12 months depending on the patient.

After starting levothyroxine or changing its dose, TSH should be checked about 6–8 weeks later. This window matches how long it takes for the body's thyroid axis to reach a new steady state after a dose change, so TSH accurately reflects whether the replacement dose is appropriate. Checking sooner—like within 24–48 hours—won’t show the full effect, since TSH lags behind changes in thyroid hormone levels. Waiting much longer (months to a year) delays optimization and can keep patients hypo- or hyperthyroid longer than necessary. If the TSH is not in range at 6–8 weeks, adjust the dose and recheck in another 6–8 weeks. Once a stable dose and TSH are achieved, monitoring typically occurs every 6–12 months depending on the patient.