Levothyroxine

Pronounced lee-vo-thy-ROX-een

Brand names: Synthroid, Levoxyl

Type: Thyroid hormone replacement · All Hormone & Endocrine Medicines

What Levothyroxine is used for

• Underactive thyroid (hypothyroidism)
• After thyroid removal or radioactive iodine treatment
• Certain thyroid cancers

Common side effects

• Rapid heartbeat
• Anxiety or shakiness
• Weight loss
• Heat intolerance
• Hair shedding when starting

Important cautions

• Too much causes symptoms of an overactive thyroid and can strain the heart and weaken bones over time
• Iron, calcium, and some stomach medicines block its absorption — they are usually taken at separate times
• Blood tests (TSH) guide the dose, and brand or formulation changes should be mentioned to your care team

How it comes

Tablets, capsules, liquid, injection (hospital). This guide lists forms only — it never lists strengths or doses.