Levothyroxine vs. Nature-Throid
See how Levothyroxine and Nature-Throid compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Levothyroxine is FDA-approved and contains only T4, while Nature-Throid is a non-FDA-approved desiccated thyroid product containing both T4 and T3.
Both drugs treat hypothyroidism, but only levothyroxine has gone through formal FDA review for safety, purity, and consistent potency batch to batch.
Nature-Throid has faced repeated supply shortages, including a 2020 recall for subpotent tablets, making levothyroxine the more reliably available option.
Levothyroxine vs. Nature-Throid Drug Summary
Levothyroxine
Levothyroxine is a synthetic form of thyroid hormone (T4) used to treat hypothyroidism and to suppress TSH after thyroid cancer treatment. It's taken as a once-daily tablet, capsule, or injection, with the dose adjusted based on regular TSH and T4 blood tests.
Nature-Throid
Nature-Throid is a desiccated thyroid hormone made from porcine thyroid glands, containing both T4 and T3 along with trace amounts of other thyroid compounds. It's taken as a once-daily tablet to treat hypothyroidism and suppress TSH in certain thyroid conditions, though it has never received formal FDA approval.
Levothyroxine vs. Nature-Throid Side Effects
Levothyroxine
Nature-Throid
Levothyroxine vs. Nature-Throid Dosage
Levothyroxine
Nature-Throid
| STAGE | DOSE | WHEN |
| Starting dose | 12.5-25 mcg once daily | Weeks 1-6 |
| Maximum dose | 1.6 mcg/kg once daily | If needed |
| Dose changes | 2 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 15 mg (1/4 grain) daily | At the start |
| Maximum dose | 60-120 mg (1-2 grain) daily | If needed |
| Dose changes | 2 increases | As tolerated |
Levothyroxine
| STAGE | DOSE | WHEN |
| Starting dose | 12.5-25 mcg once daily | Weeks 1-6 |
| Maximum dose | 1.6 mcg/kg once daily | If needed |
| Dose changes | 2 increases | As tolerated |
Nature-Throid
| STAGE | DOSE | WHEN |
| Starting dose | 15 mg (1/4 grain) daily | At the start |
| Maximum dose | 60-120 mg (1-2 grain) daily | If needed |
| Dose changes | 2 increases | As tolerated |
Levothyroxine vs. Nature-Throid Indications
Levothyroxine
Levothyroxine replaces the thyroid hormone the body can't make enough of on its own, treating hypothyroidism from any cause affecting the thyroid, pituitary, or hypothalamus. It's also used to suppress TSH production after thyroid cancer treatment. It carries a boxed warning against use for weight loss, since doses beyond hormonal needs can cause serious harm.
Primary, secondary, or tertiary hypothyroidism
TSH suppression in thyroid cancer management
Not approved for weight loss (boxed warning)
Nature-Throid
Nature-Throid treats hypothyroidism from nearly any cause except the transient thyroiditis recovery phase, and it's used to suppress TSH in conditions like goiters, thyroid nodules, and Hashimoto's disease. It's also used as an adjunct in thyroid cancer management and as a diagnostic agent in thyroid suppression testing. Like levothyroxine, it's not approved for weight loss and can cause serious toxicity at doses beyond what the body needs.
Hypothyroidism of any cause (except thyroiditis recovery)
TSH suppression in goiters, nodules, Hashimoto's
Adjunct in thyroid cancer management
Levothyroxine vs. Nature-Throid Pros and Cons
Levothyroxine
Levothyroxine's decades of FDA oversight mean consistent potency from batch to batch, which matters for a drug with a narrow therapeutic index. It's inexpensive as a generic and rarely affected by supply disruptions.
Pros
FDA-approved with decades of established safety data
Widely available and rarely affected by supply shortages
Contains only T4, making dose adjustments more predictable
Cons
Some patients feel T4-only therapy doesn't fully relieve symptoms
Requires the body to convert T4 to active T3 on its own
Doesn't supply T3 or trace thyroid compounds directly
Nature-Throid
Nature-Throid appeals to patients who feel that T4-only therapy doesn't fully resolve their symptoms, since it supplies T4 and T3 directly rather than relying on the body to convert one to the other. But because it was never subject to a modern FDA approval process, its potency consistency and availability have been less predictable.
Pros
Supplies both T4 and T3 directly, without relying on conversion
Some patients report symptom improvement beyond T4-only therapy
Long history of use dating back to the 1930s
Cons
Never received formal FDA approval; potency review is less rigorous
History of shortages, including a 2020 recall for subpotent tablets
Fixed T4:T3 ratio may not match individual hormone needs
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