Cytomel is a brand name of the generic drug Liothyronine, which is a synthetic form of the T3 thyroid hormone. It is being more commonly added to levothyroxine treatment, to provide both T4 and T3 as part of the thyroid hormone replacement treatment.

Thyroid replacement therapy such as Cytomel is used when the thyroid gland does not secrete enough thyroid hormone (hypothyroidism). Thyroid hormone is necessary for increasing the metabolic rate of body tissues. Cytomel works quickly to restore the normal function of tissues and organs and must be taken on a daily basis to be effective. Replacement thyroid hormone therapy usually needs to be taken for life.

Low thyroid levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery. It is important to have adequate levels of thyroid hormone in your bloodstream to maintain normal mental and physical activity.This medication is also used to lower thyroid function in certain diseases such as enlarged thyroid gland (goiter) and Hashimoto's thyroiditis. It is also used to test thyroid activity. Liothyronine is a man-made hormone that replaces the body's natural thyroid hormone (T3).

This drug may also be used to treat thyroid cancer. It has also been used to boost the effect of antidepressant medications in patients whose thyroid levels are normal. Liothyronine should not be used for treating infertility in patients with normal thyroid levels. The risks of use are high, and liothyronine provides no benefit.