Active Ingredient

Levothyroxine

Levothyroxine is a synthetic form of a hormone that is normally produced by your thyroid gland. It is commonly used to treat conditions where the thyroid does not produce enough hormone.

This medication helps restore the hormone balance in the body, which can alleviate symptoms associated with thyroid hormone deficiency.

Written By Douglas C. Goldberg, MD

Reviewed By Philip Schein, MD

Last Updated 28 Nov 2025

Available Levothyroxine Brands

Synthroid

Strengths 25mcg, 50mcg, 75mcg, 100mcg, 125mcg, 150mcg, 200mcg

Soloxine

Strengths 100 mcg

Levothyroxine Uses

Levothyroxine is primarily used to manage thyroid-related health conditions. It helps in normalizing hormone levels and improving symptoms.

Treatment of hypothyroidism
Management of goiter
Thyroid hormone replacement after thyroid surgery
Support in thyroid cancer treatment

How Levothyroxine Works

Levothyroxine works by replacing or supplementing the thyroid hormone that the body is unable to produce in sufficient amounts. This helps in maintaining the normal metabolic activities of the body.

It acts similarly to the natural hormone thyroxine (T4), promoting normal growth and development, and regulating protein, fat, and carbohydrate metabolism.

Common side effects of Levothyroxine

Not everyone experiences side effects from levothyroxine, and many side effects are mild and temporary. However, some people may experience the following:

Headache
Nervousness
Insomnia
Increased appetite
Weight loss
Sweating
Heat intolerance

If you experience serious or persistent side effects, contact your healthcare provider.

Take levothyroxine on an empty stomach for better absorption.
Avoid consuming certain foods and supplements close to the time of taking your medication, as they can affect absorption.
Inform your doctor about any other medications you are taking to avoid potential interactions.
Regular monitoring of thyroid levels through blood tests is recommended.
Avoid using levothyroxine if you experience symptoms of hyperthyroidism like rapid heartbeat or chest pain.

Always consult your healthcare provider for personalized medical advice.

Frequently Asked Questions

What does levothyroxine do?

Levothyroxine replaces or supplements the thyroid hormone, helping to maintain normal metabolic functions in the body.

How long does it take for levothyroxine to work?

It may take several weeks to notice improvement in symptoms, as the body gradually adjusts to the hormone levels.

Can I drink alcohol while taking levothyroxine?

Moderate alcohol consumption may be acceptable, but it’s best to discuss with your doctor to avoid any potential interactions.

What happens if I miss a dose of levothyroxine?

If you miss a dose, take it as soon as you remember unless it’s almost time for your next dose. Do not double the dose.

Are there any foods to avoid while taking levothyroxine?

Certain foods and supplements, like those high in calcium or iron, can affect absorption. It’s advisable to take them several hours apart from levothyroxine.