Is synthroid and levothyroxine the same?

Yes – Synthroid® is just a brand name for the generic medication levothyroxine sodium.

| What it is | Same? | Details |
|------------|-------|---------|
| Active ingredient | ✅ | Both contain the same synthetic thyroid hormone, levothyroxine. |
| FDA‑approved name | ❌ | Synthroid is the proprietary name; levothyroxine is the generic name. |
| Formulation | ✅ | The tablets are formulated to release the same dose of levothyroxine, though the inactive ingredients (binders, dyes, fillers) may differ slightly between manufacturers. |
| Dosing | ✅ | Doses are expressed in micrograms (µg) of levothyroxine, whether you buy Synthroid, levothyroxine tablets from an unrelated manufacturer, or other brand names (e.g., Levoxyl, Levoxyl, Levothroid, Tirosint, etc.). |
| Potency | ✅ | Each microgram of levothyroxine is biologically equivalent, regardless of brand. |
| Safety profile | ✅ | The same clinical profile applies. Differences are generally in cost or minor excipients; most people can switch between brands without changing the dose. |

When switching between Synthroid and a generic

- Check the label: Make sure the generic is “levothyroxine sodium” and not a different formulation (e.g., liquid levothyroxine, soft‑gel capsule, or a drug that also contains liothyronine).
- Watch your dose: Because the tablet’s formulation may vary slightly, it’s common practice to keep the same brand for a few weeks to ensure stable thyroid‑stimulating hormone (TSH) levels before switching, and then recheck labs after 6–8 weeks.
- Side effects: The side‑effect profile is identical—too little can leave you feeling fatigued, too much can cause palpitations, anxiety, weight loss, etc.

Bottom line

Synthroid and levothyroxine are chemically the same; Synthroid is a brand‑name tablet containing levothyroxine sodium. Your healthcare provider can help you decide whether you should stay on Synthroid, switch to a generic, or try a different brand—often the decision comes down to cost, insurance coverage, and personal preference.

Do you have a specific question about your dosing, lab results, or how to transition between brands?