how long does it take for levothyroxine to work

Levothyroxine starts working immediately after taking the first dose; however, it generally takes about 4 to 6 weeks to notice the full benefit and improvement in hypothyroidism symptoms. Blood tests to measure thyroid hormone levels are usually done around 4 to 6 weeks after starting treatment to assess effectiveness and adjust the dose if necessary. Some people may begin to notice symptom improvement as early as 1 to 3 weeks, but peak effects typically occur at 4 to 6 weeks. It is important to take levothyroxine on an empty stomach and consistently at the same time daily for best absorption and effectiveness.