What is the brand name for Levothyroxine?
The brand name for Levothyroxine is Synthroid.
PTCB TOP 200 · #3
Levothyroxine
Synthroid
Levothyroxine is the generic name for the brand-name drug Synthroid. It is a thyroid hormone used to treat hypothyroidism. On the PTCE Top 200 drug list, Levothyroxine ranks #3 and is one of the most frequently tested endocrine medications — commonly quizzed on its brand–generic pair, drug class, and key side effects.
| Generic name | Levothyroxine |
|---|---|
| Brand name(s) | Synthroid |
| Drug class | Thyroid hormone |
| Class group | Endocrine |
| Common use | hypothyroidism |
| DEA schedule | Unscheduled |
| Availability | Prescription only (Rx) |
What is Levothyroxine used for?
Replaces thyroid hormone for hypothyroidism. Also used to suppress TSH in certain thyroid cancer/goiter settings.
What drug class is Levothyroxine?
Levothyroxine is a Thyroid hormone in the Endocrine group. Knowing the class is the fastest way to predict its uses, side effects, and the brand↔generic pairs the PTCE tests.
Common side effects of Levothyroxine
- arrow_rightPalpitations
- arrow_rightTremor
- arrow_rightInsomnia
- arrow_rightHeat intolerance/sweating
- arrow_rightWeight loss (if over‑replaced)
Major interactions
- arrow_rightCalcium/iron supplements and antacids bind levothyroxine and reduce absorption (separate dosing)
- arrow_rightBile‑acid sequestrants (cholestyramine/colesevelam) reduce absorption
- arrow_rightWarfarin effect may increase when thyroid status changes
- arrow_rightEnzyme inducers (e.g., rifampin, carbamazepine) may increase clearance
Is Levothyroxine a controlled substance?
No. Levothyroxine is not a federally controlled substance (it is unscheduled by the DEA).
warning Boxed warning
BOXED WARNING: Not for treatment of obesity or for weight loss in patients with normal thyroid function.
How to remember Levothyroxine (PTCE mnemonic)
SYNTHroid SYNTHesizes thyroid — LEVO = 'level' the thyroid. Empty stomach AM, separate from calcium/iron; never for weight loss.
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PTCE exam tip
Levothyroxine replaces thyroid hormone for hypothyroidism. Brand consistency matters, and it's a classic “take on an empty stomach” counseling point.
Levothyroxine FAQ
What is Levothyroxine used for?
Levothyroxine is used to treat hypothyroidism. Replaces thyroid hormone for hypothyroidism. Also used to suppress TSH in certain thyroid cancer/goiter settings.
What drug class is Levothyroxine?
Levothyroxine is a Thyroid hormone (Endocrine group).
Is Levothyroxine a controlled substance?
No. Levothyroxine is not a federally controlled substance (it is unscheduled by the DEA).
Study guides that cover Levothyroxine
Free, in-depth guides to the patterns behind this drug — no app needed.
Drug suffix cheat sheetthe suffix that gives away this drug's class
How to memorize the Top 200 drugsa method for locking in brand↔generic pairs
Pharmacy math cheat sheetthe five calculation types the PTCE asks
What changed on the 2026 PTCB examthe new domain weights for 2026See all PTCE study guides or browse the full Top 200 drug list.
Drill Levothyroxine the way the PTCE asks it
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Related drugs in the Endocrine group
Last reviewed August 7, 2026. Educational use only — not medical advice. Verify clinical specifics with your pharmacist or a current label source such as DailyMed. RxReflex is not affiliated with or endorsed by the Pharmacy Technician Certification Board (PTCB).