Skip to main content

How long does Cytomel take to start working?

Medically reviewed by Carmen Pope, BPharm. Last updated on Aug 14, 2023.

Official answer


Cytomel starts working within a few hours, but its maximum effect can take two to three days to occur. It only takes 4 hours for 95% of a dose of Cytomel to be totally absorbed. If you are taking Cytomel daily, then after a few days it will work continuously, without any drop in effect, and you should notice a reduction in your symptoms of hypothyroidism within 2 to 3 days of starting Cytomel. Symptoms of hypothyroidism include tiredness, increased sensitivity to cold, constipation, and dry skin.

Cytomel contains liothyronine in a sodium salt form (also called LT3) which is a man-made form of one of our naturally occurring thyroid hormones, also called liothyronine. Cytomel may be used to increase levels of thyroid hormone in the body and treat hypothyroidism (low thyroid levels). It may also be given to help manage thyroid cancer in addition to surgery and radiotherapy, or to help diagnose conditions such as mild hyperthyroidism (high thyroid levels).

  • Cytomel. Updated 06/2021. Pfizer Laboratories Div Pfizer Inc

Read next

Related medical questions

Drug information

Related support groups