Levothyroxine (Levothyroxine sodium) — Uses, Dosage, Side Effects & Safety

Drug class: Thyroid hormone replacement

Overview

Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4), used to treat hypothyroidism—a condition where the thyroid gland does not produce enough hormones for the body's needs. It helps restore normal energy levels, metabolism, and growth by replacing or supplementing the natural thyroid hormone. This medication is also used to help manage or prevent goiter (enlarged thyroid gland) and is sometimes prescribed as part of the treatment for certain types of thyroid cancer. Levothyroxine works by providing the body with a steady supply of thyroid hormone, which is essential for regulating metabolism, heart function, and many other bodily processes. Key points for patients: Take levothyroxine exactly as prescribed, usually on an empty stomach, and avoid taking it with certain foods or medications that can interfere with absorption. Regular blood tests are needed to ensure the dose is correct.

Therapeutic uses

• Hypothyroidism
• Thyroid stimulating hormone (TSH) suppression in thyroid cancer
• Goiter
• Myxedema coma

Common side effects

• Palpitations
• Tremor
• Insomnia
• Weight loss
• Diarrhea
• Heat intolerance
• Chest pain

Frequently Asked Questions about Levothyroxine

How long does it take for levothyroxine to work?

Most people begin to notice improvement in symptoms within 1–2 weeks, but full effects may take several weeks. Regular blood tests help ensure the dose is correct.

Can I take levothyroxine with food or coffee?

No. Levothyroxine should be taken on an empty stomach, at least 30–60 minutes before food or coffee, as these can reduce absorption.

What should I do if I become pregnant while taking levothyroxine?

Inform your doctor immediately. Thyroid hormone needs often increase during pregnancy, and your dose may need adjustment. Do not stop taking levothyroxine.

Can levothyroxine be used for weight loss?

No. Levothyroxine should not be used for weight loss in people with normal thyroid function. Misuse can cause serious health risks.

What lab tests are needed while taking levothyroxine?

Thyroid function tests (TSH, free T4) are required regularly to monitor and adjust your dose.

Are there any foods or supplements I should avoid?

Avoid taking calcium, iron, soy, and high-fiber foods close to your dose, as they can interfere with absorption. Separate by at least 4 hours.

Is it safe to switch between different brands of levothyroxine?

Switching brands can affect thyroid hormone levels. Always consult your doctor before changing brands, and monitor thyroid function closely.

Educational information only. Always consult a qualified healthcare professional before starting, stopping, or changing any medication.