Finding the correct dosage of your thyroid medication, such as levothyroxine, is a personalised process managed by your doctor. It is primarily determined through a simple blood test that measures your Thyroid Stimulating Hormone (TSH) levels, sometimes alongside Free T4. Your doctor will calculate a starting dose based on factors like your weight, age, and health history. After six to eight weeks, you will get a follow-up blood test to see how your body has responded. Your doctor will then gradually adjust the dosage until your thyroid hormone levels are stable and in the healthy, normal range.

Your TSH of 5.5 is only mildly elevated, which is very common and not a cause for alarm. To help determine if you need medication, you should request Free T4 and Free T3 tests. Free hormone tests measure the active, unbound thyroid hormones in your blood, providing a much more accurate picture of your actual thyroid function. Total T3 and T4 levels can be easily affected by other factors like medications, hormone levels, or liver proteins, making them less reliable. Along with Free T4, your doctor might also check thyroid antibodies to decide if starting a low dose of thyroid hormone (like levothyroxine) is necessary for you.