In my experience and talking with doctors it usually takes about one month for the change in thyroid levels to stabilize. Then it takes another month for the TSH to adjust. When my doctor changes my thyroid medication he wants to see me in 3 months for blood testing. He said anything early will not be accurate. When I'm hypo and there is an increase in my thyroid levels I usually feel better in about 1-2 weeks. Remember, thyroid level and TSH levels change slowly. These hormones affect the entire body’s metabolism. You don't want this to change fast.