Brief Answer: Thyroid Detailed Answer: The best way to tell if you are getting too much of thyroid dose is to go by the TSH in your lab test. If the value falls consistently below 0.4, especially along with free T4 higher than upper limit of normal, it is a clear indication that the dose is excessive for your body. This approach is applicable to the most common form of hypothyroidism in the world ie Primary hypothyroidism as opposed to the rare secondary hypothyroidism in which the pituitary does not function adequately. Also if you are on steroids or opioid pain killers then that can lower the TSH and in these instances it is a bit trickier to go by the TSH values. In general, most women need around a 100 mcg but again the best way is to go by the TSH in the situations described above. Weight based calculations have been proposed and endocrinologists sometime use 1.6 mcg per kg body weight as a rough guide to estimate an individuals requirements. Keep in mind this is kilogram based, not in pounds. So for example a 100 kg person = 220 pounds, will likely require 160 mcg daily as a possible replacement dose. However, it is a useful guide and most endocrinologists follow the lab values as well the person's well being

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