How Long Does It Take for Levothyroxine to Work?

How Long Does It Take for Levothyroxine to Work

How Long Does It Take for Levothyroxine to Work?

The thyroid gland is a key element of the endocrine system. It’s crucial in regulating the body’s metabolism and hormone levels. The thyroid gland produces two essential hormones, thyroxine (T4) and triiodothyronine (T3), that help control the body’s sensitivity, heart rate, and temperature.

When the thyroid gland doesn’t produce enough hormones, it can cause a condition known as hypothyroidism. Symptoms of hypothyroidism include fatigue, muscle aches, cold intolerance, weight gain, memory problems, and elevated cholesterol levels. In addition to these symptoms, hypothyroidism can cause other problems, such as an enlarged thyroid gland (goiter), irregular menstrual periods, and fertility problems.

One of the most common medications used for treating hypothyroidism is called levothyroxine.

In this article, we will talk about hypothyroidism and address some common questions, such as how long does it take for levothyroxine to work in detail:

Causes of Hypothyroidism

There are several possible causes of an underactive thyroid gland (hypothyroidism), including autoimmune disorders, radiation treatment, and surgical removal of the thyroid gland. The potential causes of hyperthyroidism include:

  • Hashimoto’s thyroiditis is an autoimmune disorder where the body’s immune system attacks the thyroid gland; as a result, it produces less thyroid hormone.
  • Surgical removal of the thyroid gland – If it is removed completely or partially, it can no longer produce thyroid hormones, leading to hypothyroidism.
  • Treatment for hyperthyroidism – In some cases, treatment for an overactive thyroid gland can lead to hypothyroidism. For example, if the thyroid gland is removed surgically or destroyed with radioactive iodine, it will no longer be able to produce thyroid hormones.
  • Congenital hypothyroidism – This condition is caused at birth when the thyroid gland doesn’t develop properly or is missing altogether.

Treatment of Hypothyroidism

Levothyroxine is a renowned medication used to treat hypothyroidism. It’s a synthetic form of the thyroid hormone thyroxine (T4), which is normally produced by the body. Levothyroxine helps replace the missing thyroid hormones, restores normal hormone levels in the body, and can help relieve symptoms.

Levothyroxine is typically taken orally and once daily. It is important to take the medication as prescribed and to have regular blood tests to monitor hormone levels.

If you have been prescribed levothyroxine and are curious to know how long does it take for levothyroxine to work, then read below.

How Long Does It Take for Levothyroxine to Work?

Knowing exactly how long does it take for levothyroxine to work is difficult. It depends on several factors, such as the individual’s age, overall health, and the severity of hypothyroidism.

Most people notice an improvement in their symptoms within the first week of starting treatment with levothyroxine. However, it may take several weeks or even months for the medication to reach its full effect.

It’s important to note that even after levothyroxine begins to work, it is typically taken on a long-term basis. That’s because the body takes time to adjust to the increased levels of thyroid hormone, and it can take some time for the hormone to reach all the cells in the body.

The best way to determine how long does it take for levothyroxine to work is to consult your doctor and follow their recommendations for dosing and monitoring.

Mechanism of Action

When levothyroxine is taken orally, it’s absorbed into the bloodstream and travels to the thyroid gland. Once there, it is converted into the active thyroid hormone T4, which is responsible for regulating the body’s metabolism and other essential functions.

By restoring normal thyroid hormone levels in the body, levothyroxine can help relieve hypothyroidism symptoms and improve your overall health.

Dose and Benefits of Taking Levothyroxine at Night

The dose of levothyroxine depends upon the severity of your hypothyroidism. However, the dosage is not standardized for everyone, but an average starting dose is about 25-50 mcg daily. The starting dose is typically low and gradually increases until the thyroid hormone levels in the body are normalized.

The dosage may need to be adjusted over time to maintain the proper thyroid hormone levels. That’s because a person’s hormone needs can change due to age, pregnancy, and certain medical conditions.

The time-of-day levothyroxine is taken also dictates its effectiveness. Research suggests that taking levothyroxine at night may be more effective than taking it in the morning. That’s because the body’s metabolism naturally slows down at night, allowing the medication to be more easily absorbed and processed by the body. Taking levothyroxine at night may also help avoid potential interactions with other medications or foods a person may be taking or eating during the day.

Who Can and Cannot Take levothyroxine?

Levothyroxine is undoubtedly a safe and effective treatment for hypothyroidism, but it is not for everyone. Following people should avoid it:

  • Levothyroxine may not be safe for people with certain medical conditions, such as an adrenal gland disorder or heart disease.
  • Levothyroxine comprises inactive ingredients which cause allergic reactions in some individuals. If you’re allergic to any of the ingredients in levothyroxine, you should not take it.
  • Lastly, levothyroxine may not be safe for pregnant or breastfeeding women.

So, talk to your doctor before starting levothyroxine to determine whether it is appropriate for you. They can provide the best guidance and advice based on your situation.

Dietary Instructions While Taking Levothyroxine

While taking levothyroxine, it is important to avoid certain foods and medications that can interfere with its absorption and effectiveness. These include:

  • Calcium and iron supplements can bind to levothyroxine in the stomach and intestines and prevent it from being absorbed into the body. Taking these supplements at least 4 hours before or after taking levothyroxine is best.
  • Soy contains substances that can interfere with the absorption of levothyroxine. So, avoid taking levothyroxine at the same time as soy products or take them at least 4 hours apart.
  • High-fiber foods, such as bran, wheat bran, and some fruits and vegetables, are also found to reduce the absorption of levothyroxine. So, take them at least 4 hours apart.

How Do You Know if Levothyroxine is Working?

The medication is working if you’re taking levothyroxine as prescribed and your thyroid hormone levels are within the normal range. Apart from your normalized thyroid levels, the following signs also indicate your progress:

  • Your symptoms are improving – If you have been experiencing symptoms of hypothyroidism, such as fatigue, weight gain, and cold intolerance, you may notice an improvement in these symptoms as your thyroid hormone levels normalize.
  • You are feeling more energetic – As your thyroid hormone levels improve, you may notice an increase in energy levels. It can signify that the medication is working and your body’s metabolism is improving.
  • You can maintain a healthy weight – One of the main functions of thyroid hormones is to regulate the body’s metabolism. As your thyroid hormone levels improve, you may find it easier to maintain a healthy weight.


Levothyroxine is a safe and effective medicine for treating hypothyroidism. Are you still wondering how long does it take for levothyroxine to work? Although you may notice a significant improvement in your symptoms within the first week of starting treatment, it may take several weeks or even months for the medication to reach its full effect.

Remember that hypothyroidism is a treatable condition and can be managed successfully with lifestyle changes, diet, and medication.


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