How long after starting levothyroxine should thyroid function be rechecked?

How long after starting levothyroxine should thyroid function be rechecked?

• A. 2 weeks
• B. 4-6 weeks
• C. 12 weeks
• D. 6-8 weeks

Answer: (D)

After starting levothyroxine, the body needs time to reach a new hormonal steady state. Levothyroxine has a half-life of about a week, so it takes several weeks for levels to stabilize and for the pituitary to adjust its TSH output. Rechecking thyroid function at 6–8 weeks allows TSH and free T4 to reflect the new dose and helps guide safe dose adjustments. If checked too early, results can be misleading because hormones haven’t settled; waiting longer (e.g., 12 weeks) may delay needed changes if symptoms persist. Therefore, 6–8 weeks is the appropriate interval for rechecking.

After starting levothyroxine, the body needs time to reach a new hormonal steady state. Levothyroxine has a half-life of about a week, so it takes several weeks for levels to stabilize and for the pituitary to adjust its TSH output. Rechecking thyroid function at 6–8 weeks allows TSH and free T4 to reflect the new dose and helps guide safe dose adjustments. If checked too early, results can be misleading because hormones haven’t settled; waiting longer (e.g., 12 weeks) may delay needed changes if symptoms persist. Therefore, 6–8 weeks is the appropriate interval for rechecking.