The Dose That's Right for You
To achieve thyroid hormone balance, the American Association of Clinical Endocrinologists and the American Thyroid Association recommend patients receiving levothyroxine therapy such as Synthroid keep their thyroid-stimulating hormone (TSH) levels between 0.45 and 4.12 mIU/L. Some doctors may recommend a different range for their patients. Your treatment needs are unique – you may require a little more or a little less Synthroid than the next person to stay in this target range.
When you start taking Synthroid, it’s very important for your doctor to monitor you closely – usually testing your TSH level every 6-8 weeks – to make sure you’re on the right dose. This is because Synthroid is a narrow therapeutic index drug, which means if your dosage is off even a little bit, it can throw off your TSH level and cause side effects. You might hear this referred to as under-replacement or under-treatment (when your levothyroxine dose is too low), and over-replacement or over-treatment (when your levothyroxine dose is too high). Our Symptom Profiler tool can help you recognize symptoms of under-replacement and over-replacement.
Watch this video to learn more about how your doctor finds the Synthroid dose that is right for you, and what you can expect from treatment.
Once you and your doctor have found your precise Synthroid dose, it’s important to stay consistent with your treatment. This means taking Synthroid as prescribed every day.
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1. Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988-1028.
2. National Association of Boards of Pharmacy. Survey of Pharmacy Law. 2008.