Synthroid
Generic: levothyroxine
Also known as: others
Class
Drug (Wikipedia)
Form
N/A
Route
By mouth, intravenous
Manufacturer
Various manufacturers
scienceActive Ingredients
| Ingredient | Strength |
|---|---|
| (''S'')-2-Amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoic acid |
healingIndications & Usage
Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T4). It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma. It may also be used to treat and prevent certain types of thyroid tumors. It is not indicated for weight loss. Levothyroxine is taken orally (by mouth) or given by intravenous injection. Levothyroxine has a half-life of 7.5 days when taken daily, so about six weeks is required for it to reach a steady level in the blood. Side effects from excessive doses include weight loss, trouble tolerating heat, sweating, anxiety, trouble sleeping, tremor, and fast heart rate. Use is not recommended in people who have had a recent heart attack. Use during pregnancy has been found to be safe. Dosing should be based on regular measurements of thyroid-stimulating hormone (TSH) and T4 levels in the blood. Much of the effect of levothyroxine is following its conversion to triiodothyronine (T3). Levothyroxine was first made in 1927. It is on the World Health Organization's List of Essential Medicines. Levothyroxine is available as a generic medication. In 2023, it was the third most commonly...
scheduleDosage & Administration
Consult prescribing information or healthcare provider for dosage.
warningWarnings
Information from Wikipedia. Always verify with official sources and consult a healthcare professional.
reportAdverse Reactions
See Wikipedia article for reported adverse reactions.
blockContraindications
Consult prescribing information for contraindications.
compare_arrowsDrug Interactions
Consult prescribing information for drug interactions.
gavelLegal Status by Country
| Country | Legal Status | Prescription | Notes |
|---|---|---|---|
| United States | Varies | Check FDA | Consult healthcare provider |
infoLegal status may change. Always verify with local authorities before traveling internationally with medication.
scienceScientific References
- verified
FDA Drug Label
View on DailyMedopen_in_new - article
PubMed Research
Search PubMed for studiesopen_in_new
helpFrequently Asked Questions
Data Sources
This information is sourced from the FDA's public drug database (OpenFDA) and the National Library of Medicine's RxNorm API. Data was last updated on Nov 29, 2025.
FDA Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult a healthcare professional before starting, stopping, or changing any medication. The information provided may not cover all possible uses, actions, precautions, side effects, or interactions.