Read a thyroid conversion chart by looking up the thyroid medication and comparing the necessary dose of a specific medication to the amount of another drug necessary to provide an equivalent dose, according to About.com. Equivalent doses are based on drug strength.
Manufacturers express doses of various thyroid drugs by the grain, microgram or milligram, according the About.com's conversion chart. Taking the exact dose needed is important in controlling thyroid disease, and only a doctor can determine the correct dose through conducting physical exams and blood tests, states the Food and Drug Administration. Side effects of taking the wrong dose include nervousness and weight loss, irritability, a rapid heartbeat and anxiety.
Various brands of FDA-approved drugs exist to treat thyroid disease, as listed by About.com. Some treat an underactive thyroid, or hypothyroidism, by providing either a natural or a synthetic replacement hormone, while others, called antithyroid medications, treat an overactive thyroid, called hyperthyroidism.
Generic versions of thyroid drugs are as effective as name-brand versions, but there have been concerns that generic versions of some medications are not as effective as the brand-name medications, as stated by the FDA. As of 2015, this concern may not be valid, as evidence indicates that some medications lose potency over time, which may account for the variability in effects. Patients should discuss any medication change with their doctors.