What Is Unithroid? Uses, Dosage, and What You Need to Know in 2026

Unithroid is a brand-name prescription thyroid hormone medication. It was the first levothyroxine product to receive FDA approval under a New Drug Application in August 2000 — making it the original reference standard for all other levothyroxine brands and generics. Today it remains one of several trusted brand-name options for patients with thyroid conditions.

What Is Unithroid?

Unithroid (levothyroxine sodium, USP) is a synthetic form of T4 — the principal thyroid hormone naturally produced by the human thyroid gland. It is manufactured by Jerome Stevens Pharmaceuticals (JSP), a US-based family-owned company in Bohemia, New York, and distributed by Amneal Pharmaceuticals.

The active ingredient, levothyroxine sodium, is chemically identical to the T4 hormone your thyroid gland would normally produce. When you take Unithroid, you are essentially giving your body the thyroid hormone it cannot make enough of on its own.

What Conditions Does Unithroid Treat?

Unithroid is FDA-approved for two main indications:

Hypothyroidism: The most common use. Unithroid replaces thyroid hormone in patients with underactive thyroid glands, whether caused by primary thyroid failure, pituitary disease, Hashimoto's thyroiditis, post-thyroidectomy (after surgical removal of the thyroid), or congenital hypothyroidism.

TSH suppression for thyroid cancer: Used as an adjunct to surgery and radioiodine therapy in managing thyrotropin-dependent well-differentiated thyroid cancer. Higher than replacement doses are used to suppress TSH and reduce the stimulus for thyroid cancer cell growth.

Common off-label or related uses include: goiter treatment/prevention, management of Hashimoto's thyroiditis even with borderline TSH, and management of thyroid nodules in certain cases.

What Doses Does Unithroid Come In?

Unithroid is available in 12 tablet strengths, covering a broad range of doses:

25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Each strength is color-coded with different dyes for easy identification. The 300 mcg tablet (Unithroid Direct) is a scored tablet. The typical adult replacement dose is approximately 1.6 mcg/kg/day, which for a 70 kg adult is roughly 112-125 mcg/day.

How to Take Unithroid Correctly

How you take Unithroid is almost as important as taking the right dose. Follow these guidelines for best results:

Take on an empty stomach: Take Unithroid in the morning, at least 30-60 minutes before eating. Food significantly reduces levothyroxine absorption.

Take with water only: Take with a full glass of water. Do not take with coffee, juice, or other beverages.

Separate from supplements by 4 hours: Calcium supplements, iron supplements, antacids, and multivitamins reduce levothyroxine absorption. Take Unithroid at least 4 hours before or after these.

Take it every day: Unithroid has a long half-life (~7 days), so missing an occasional dose is less critical than with short-acting drugs. However, consistent daily dosing is important for stable thyroid levels.

Infants and children: If a child cannot swallow tablets, crush the tablet and mix with a small amount (5-10 mL) of water immediately before giving. Do not store the suspension. Do not mix with soy formula.

What Makes Unithroid Different from Other Levothyroxine Brands?

All brand-name levothyroxine products contain the same active ingredient. What differentiates Unithroid from competitors like Synthroid, Levoxyl, Euthyrox, and Tirosint are:

Historical first-mover status: Unithroid was the first levothyroxine product to receive FDA NDA approval (August 2000) and served as the reference drug for all other levothyroxine approvals.

US-based manufacturing: Jerome Stevens Pharmaceuticals operates exclusively in the US, which provides a more stable domestic supply chain.

Inactive ingredients: Unithroid contains lactose, acacia, corn starch, microcrystalline cellulose, magnesium stearate, sodium starch glycolate, and colloidal silicon dioxide. Patients with lactose intolerance should note this; Tirosint is a better option in that case.

Amneal distribution: Unithroid is distributed by Amneal Pharmaceuticals, with a dedicated copay assistance program for commercially insured patients.

For a deeper dive into how Unithroid works at the cellular level, see our guide on how Unithroid works.