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Does Levothyroxine Cause Hair Loss?

What to do if you notice hair loss after starting levothyroxine to treat hypothyroidism.
Does Levothyroxine Cause Hair Loss?

Medically Reviewed by:
Medically Reviewed by:

In this article:

  • Understanding the hair growth cycle
  • How does hypothyroidism cause hair loss?
  • Shouldn't levothyroxine treat my hair loss?
  • How to slow or reverse hair loss


Off-kilter hormones can easily disrupt the delicate hair growth cycle. This disruption is especially true for thyroid hormones, which are responsible for regulating the cellular growth and metabolism of every cell in your body. Hair loss is a common side effect of hypothyroidism, but it is a treatable problem. However, many people wonder if levothyroxine, the most commonly prescribed treatment option for hypothyroidism also causes hair loss. Ahead, a look at if levothyroxine causes hair loss.


Understanding the hair growth cycle


There are three primary phases of the hair growth cycle: anagen, catagen, and telogen. Every strand on your head follows its own growth cycle, which means that you will not lose all your hair at one time when they switch to the shedding phase. 

Chart of the hair growth cycle with graphics illustrations of each stage


Anagen is the growing phase of hair growth, and it typically lasts between 4-7 years. Certain factors can interrupt the anagen phase, including stress, illness, and significant hormone fluctuations.


Catagen is a quick resting phase that lasts about two weeks. During this phase, the hair follicle stops growing and waits for the bulb to begin detaching in your scalp.


Telogen is the final phase of the hair growth cycle. The strand fully detaches from your scalp and eventually sheds. This phase usually lasts three months and ends with the hair falling out. After these three months, a new follicle will begin to grow, starting the process all over again.


How does hypothyroidism cause hair loss?


Hypothyroidism is the condition in which the thyroid gland does not produce enough thyroid hormone. Thyroid hormones are responsible for regulating the body's metabolic rate including controlling heart, muscle and digestive functions, brain development, and bone maintenance. When not enough thyroid hormone circulates in your body, your cells cannot keep up with normal processes. 


Low thyroid hormones can interfere with the hair growth cycle by shortening the anagen phase and delaying the start of a new follicle from growing. Thus, more hair than normal can be in the resting phase, making your hair thinner. Low thyroid hormone levels can also cause your hair to become brittle and dry, making it look even more sparse.


Shouldn't levothyroxine treat hair loss?


Levothyroxine is a thyroid medication prescribed to treat low thyroid hormone levels. It is a synthetic form of thyroid hormone that mimics human thyroid hormone. One would imagine that once you correct low thyroid hormone levels, you would see an improvement in your hypothyroid symptoms, including hair loss. However, some people find their hair loss worsens when they start levothyroxine.


While this may be concerning, especially if you are already struggling with hair loss, rest assured increased shedding after starting levothyroxine is usually short-lived. Most people who notice more hair loss after starting levothyroxine find that it lasts only a month or two. 


Additional shedding sometimes happens because the hormones need time to stabilize. The hair growth cycle takes time to adjust to changes in your system. 


Rest assured, once you are on the correct dose of medication, most hair loss will cease. You should return to having a normal hair growth cycle unless there is another cause of your hair loss, like androgenic alopecia, for instance. 


How to slow or reverse hair loss


The best way to restore your hair is to treat underlying conditions like hypothyroidism. Although it can be hard to wait, be patient with your body as it learns to adjust to your thyroid medication. 


Aside from medication, there are several other steps you can take to boost hair thickness and growth.


Eat a well-balanced diet

Hair requires plenty of nutrients that are abundant in wholesome foods like vegetables, fruits, and meat. To increase the rate your hair grows and for more density, eat foods with plenty of iron, keratin, zinc, and vitamins A, B, C, D, and E. 


If you try a supplement to boost your nutrient intake, you may wish to look for one with biotin. Bear in mind that biotin can interfere with some thyroid lab results, so check with your lab to ask if you should avoid taking biotin before testing your thyroid.


Note: Paloma Health's lab uses a specialized assay, so there is no need to delay your medications or supplements, including biotin. You may also take the Paloma Health at-home thyroid test with or without regard to food, so no need to fast.


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Limit harsh styling practices

Coloring, permanents, and hot styling tools are some of the most harmful things you can do for your hair. However, many of us use these practices to get the look we want. If you style your hair with anything that may cause damage, try to limit it as much as possible. 


For example, if you blow-dry your hair every day, try to space out washing and wear your hair in a style that works with 'dirty' hair. Or, if you color your hair, try to separate treatments by an additional week or two so your hair has more time to recover.


Treat any underlying scalp infections

Scalp infections like seborrheic dermatitis (a leading cause of dandruff), psoriasis, or fungal infections can lead to more hair loss. Treating your thyroid will not help treat these scalp infections. You will need to seek care from a dermatologist who can help prevent these conditions from causing more inflammation and hair loss. 


If you are concerned about hair loss, it may be time to check your thyroid. To get started, try an at-home thyroid test kit or meet with a trusted Paloma Health thyroid doctor to optimize your thyroid health.

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