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Does levothyroxine cause hair loss?

Medically reviewed by Carmen Pope, BPharm. Last updated on Aug 25, 2022.

Official answer


Yes, levothyroxine, the main treatment for a sluggish thyroid gland, may cause hair loss in addition to other side effects. You may experience partial hair loss in the first few months of treatment, but this usually resolves and hair growth goes back to normal within a short time.

People with thyroid disease commonly experience hair loss, and taking levothyroxine can initially increase this hair loss. This is because hair growth depends on proper functioning of the thyroid gland. When you have an overactive thyroid and have too much thyroid hormone, the hair on your head can become fine, and you may experience widespread hair thinning over your entire scalp. When you have an underactive thyroid and produce too little thyroid hormone, you can lose hair not just on your scalp but everywhere on your body.

Hair loss with levothyroxine is common during the first month of treatment and is particularly common in children. Once thyroid hormone levels stabilize hair growth usually resumes.

Levothyroxine is the name of all man-made forms of the thyroid hormone T4. It mimics the hormone that is produced by the thyroid. Brand names include:

  • Synthroid
  • Levoxyl
  • Unithroid
  • Tirosint
  • Levo-T

In addition to hair loss, more common levothyroxine side effects may include:

  • Weight changes
  • Headache
  • Upset stomach
  • Fever
  • Menstrual cycle changes
  • Heat sensitivity
  • Joint pain
  • Leg cramps
  • Heat intolerance

Sometimes more serious side effects can also occur with levothyroxine use, including:

  • Shortness of breath
  • Increased heart rate and chest pain
  • Hives, rash or itching
  • Swelling of the hands, feet, ankles or lower legs
  • Flushing
  • Stomach pain, nausea or vomiting
  • Trouble keeping blood sugar under control if you have diabetes
  • Weakened bones

Hypothyroidism, or an underactive thyroid, occurs when the thyroid gland is no longer producing enough thyroid hormone, and as a result can’t regulate many of the body's key functions, including heart rate, breathing, weight, digestion and mood.

Common causes of hypothyroidism include an autoimmune disease like Hashimoto’s thyroiditis, the surgical removal of the thyroid gland or radiation treatment to the chest and neck area.

Symptoms of hypothyroidism may include fatigue, weight gain, feeling cold, thinning hair and depression, among others.

Related questions

  1. U.S. National Library of Medicine MedlinePlus. Levothyroxine. 2022. Available at: [Accessed August 25, 2022].
  2. U.S. National Library of Medicine MedlinePlus. Hypothyroidism. 2022 Available at: [Accessed August 25, 2022].
  3. U.S. Food and Drug Administration. Tyrosant. December 2017. Available at: [Accessed August 25, 2022].

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