Metoprolol IR to ER + TSH recheck (16 wks update): Background: I had hypertension and a fast resting rate with palpitations — what worked for others here?
Background: I had hypertension and a fast resting rate with palpitations. I took metoprolol tartrate 50 mg twice daily and felt wiped out by mid-afternoon. With my cardiologist, we changed to metoprolol succinate ER 100 mg once daily, taken with the evening meal, which kept the same total daily dose. Labs showed a TSH of 6.8 mIU/L and a ferritin of 18 ng/mL. My levothyroxine was increased, and I started iron under clinician direction, separated from my thyroid pill by 4 hours. At the 6-week recheck, my TSH was 2.9. My home pulse log stayed around 62-68 bpm at rest, and the afternoon crash faded by about week 10. I confirmed watch readings with a manual 60-second pulse. The lesson for me was that formulation, timing, and labs mattered together. This is one person's experience, not a dosing recommendation.
The FDA DailyMed label for metoprolol succinate ER describes once-daily dosing, while tartrate is typically dosed twice daily. The levothyroxine label advises taking it at least 4 hours apart from agents that reduce absorption, such as iron and calcium.