Levoxyl
- Manufacturer's site for this brand of levothyroxine sodium. Includes product and prescribing information, and discussion of US FDA requirements for potency and stability.
- http://www.levoxyl.com/

RXmed: Synthroid
- Information for family physicians and prescribing information.
- http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20(General%20Monographs-%20S)/SYNTHROID.html

RXMed: Eltroxin
- Product information for Glaxo Wellcome's brand of levothyroxine sodium, a synthetic hormone used in thyroid replacement therapy.
- http://www.rxmed.com/b.main/b2.pharmaceutical/b2.1.monographs/CPS-%20Monographs/CPS-%20(General%20Monographs-%20E)/ELTROXIN.html

Levothyroxine
- Information for patients from DrugDigest on dosage, usage, side effects, and interactions. Brand names include Eltroxin, Levothroid, Levoxine, Levoxyl, Synthroid, and Unithroid.
- http://www.drugdigest.org/DD/DVH/Uses/0,3915,385%7CLevothyroxine,00.html

Levothyroxine Sodium
- Information about this medication used in thyroid hormone replacement therapy, sold under brand names including Synthroid, Levoxyl, Levothroid, and Unithroid. MedicineNet State of the Art Medical Information.
- http://www.medicinenet.com/Art.asp?li=MNI&ag=Y&ArticleKey=774

Drug InfoNet - Synthroid
- Doctors answers to frequently asked questions for patients taking any form of levothyroxine.
- http://www.druginfonet.com/faq/faqsynth.htm

Synthroid
- Information for patients, healthcare providers, and pharmacists.
- http://www.synthroid.com/