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Levothyroxine sodium (brand names: Synthroid, Tirosint, Levoxyl, and others) is a prescription thyroid medication. It is used to treat hypothyroidism (underactive thyroid gland). It works by normalizing thyroid hormone levels in people whose thyroid doesn’t make enough thyroid hormone. But like most medications, levothyroxine can cause unwanted side effects, including hair loss and thinning hair. 

Please continue reading to learn more about hair loss caused by levothyroxine (thyroid hormone replacement medication). We will also talk about hair loss caused by the thyroid disease itself and what you can do about it.

Does levothyroxine cause hair loss?

Levothyroxine may cause hair loss in some people. This medicine is a synthetic version of the natural thyroid hormone thyroxine (T4). It is used to treat hypothyroidism and works by replacing thyroid hormones in people whose thyroids don’t make enough thyroid hormone. Hair loss and thinning hair can be signs of low thyroid levels (hypothyroidism). Therefore, one would expect that proper treatment of hypothyroidism with levothyroxine would also treat hair loss. 

However, some people experience worsening hair loss after starting levothyroxine treatment. This happens because thyroid hormone levels take time to stabilize. Also, the hair growth cycle needs time to adjust to the thyroid hormone levels. Increased hair fall on levothyroxine can be concerning for someone who is already experiencing hair loss. Fortunately, hair loss caused by levothyroxine is short-lived and does not typically last more than 4-8 weeks. 

Natural desiccated thyroid (Armour Thyroid, NP Thyroid, others), which is obtained from animal thyroid glands, can also cause hair loss for the same reasons.

Do thyroid hormones affect hair growth?

Research has found that thyroid hormones affect human hair growth. They are required for human hair follicle functions, including hair pigmentation, anagen prolongation, and hair matrix keratinocyte proliferation. 

In other words, thyroid hormone imbalances in the body can affect the normal hair growth cycle, and hair loss can be a sign of thyroid dysfunction. Check out our blog “8 Signs You May Have a Thyroid Condition.”

People with hypothyroidism may have a shortened anagen (active hair growth) phase and a delay in the growth of new hair follicles, causing them to lose hair at a faster rate. In addition, more hair follicles remain in the telogen (resting) phase in hypothyroid patients, causing hair thinning. Low thyroid hormones also cause other symptoms, such as coarse, dry, brittle hair, which can make the scalp hair look even more scant. 

Thyroid hormones are also linked to telogen effluvium, a condition involving prolonged hair shedding. In addition, people with alopecia areata, an autoimmune condition that causes hair loss, have a higher incidence of Hashimoto’s thyroiditis (a common cause of hypothyroidism).

Interestingly, hyperthyroidism (overactive thyroid gland) can also lead to hair loss due to a decrease in the tensile strength of the hair shafts. Therefore, thyroid disorders, both overactive and underactive thyroid, can lead to hair loss.

How to stop hair loss while on levothyroxine?

Here are some tips to stop or reduce hair loss while on levothyroxine:

Keep thyroid hormone levels in the recommended range

Levothyroxine is a synthetic form of thyroid hormone. It works by replacing thyroxine (T4) in people who don’t make enough thyroid hormones. Small changes in thyroid hormone levels can lead to significant effects on bodily functions, including hair growth. It is, therefore, important for thyroid patients to maintain thyroid hormone levels in the recommended range. Find out how long it takes for levothyroxine to work.

Your doctor will order regular blood tests to measure a TSH level while you are taking levothyroxine. They will use the results of this test to adjust the dose of medication. If your medication dosage is too high, it can cause more severe side effects, including hair loss. Read our blog to learn: What are some signs my thyroid medication is not working? 

Keep all your appointments for lab tests during levothyroxine treatment. Follow your doctor’s instructions for levothyroxine dose adjustments carefully. This will ensure your thyroid condition is under control and symptoms such as hair loss are minimized or eliminated.

Consider taking supplements that promote hair growth

Studies have found nutrient deficiencies can cause hair loss. A balanced, nutrient-rich, healthy diet is therefore essential for hair growth. If you are taking levothyroxine for hypothyroid symptoms and experiencing hair loss, it may help to take certain supplements that support hair growth, increase hair density, and reduce the rate at which hair falls. Talk to your healthcare provider about taking B vitamins, including biotin, iron, vitamin C, vitamin D, and other supplements. Learn about what foods to avoid when taking levothyroxine.

In addition to hair growth supplements, staying hydrated and eating a healthy, balanced diet can help regenerate and strengthen hair in the long run while benefiting overall health. 

Note: Biotin (vitamin B7) can support new hair growth but can also interfere with the results of thyroid function tests. Tell your doctor and laboratory personnel if you take a biotin supplement. You may need to stop it for a few days before laboratory testing for thyroid health. Find out, “how long does levothyroxine stay in your system?”

What does thyroid hair loss look like?

Thyroid hair loss is usually a diffuse hair loss affecting the entire scalp rather than localized areas (bald spots). In addition to scalp hair, hypothyroidism can also cause hair loss in the outer part of the eyebrows.

How can I control my hair fall due to thyroid?

The best way to control hair fall due to thyroid issues is to follow your doctor’s treatment plan for managing thyroid conditions. As mentioned above, thyroid hormones affect how hair grows. In people with thyroid problems, the normal hair growth cycle can be affected, leading to hair loss and hair thinning. Treating an underlying thyroid condition can help your hair grow well and remain healthy. 

If you are already on levothyroxine for hypothyroidism or antithyroid drugs for hyperthyroidism, follow your doctor’s dosing instructions carefully. Ask your healthcare provider if you don’t understand how to take the medicine properly. Too little levothyroxine may not treat hypothyroidism completely, and too much levothyroxine may cause side effects, including increased hair loss and hair thinning.