Based on NIH | Does levothyroxine contain pork or pork-derived ingredients, and is any dosage caution needed for people with pork allergies or religious dietary restrictions?

Most levothyroxine products do not contain pork-derived thyroid hormone, but some formulations may include animal‑derived excipients such as gelatin; by contrast, “desiccated thyroid” products are made from pig (porcine) thyroid and are not suitable for people avoiding pork for allergy or religious reasons. ^{[1] [2] [3] [4] [5]}

Key points at a glance

• Levothyroxine (synthetic T4) tablets: The active ingredient is synthetic and not pork‑derived, but some brands/formulations list “gelatin (unspecified)” among inactive ingredients, which may be animal‑derived. ^{[3] [4] [6]}
• Levothyroxine soft gel capsules: The capsule shell typically contains gelatin (origin not specified), which is often sourced from bovine or porcine gelatin unless a manufacturer specifically states otherwise. ^{[5] [7]}
• Desiccated thyroid (e.g., NP Thyroid): This is made from porcine thyroid glands and therefore contains pork‑derived material. ^{[1] [2]}

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Understanding the differences

Synthetic levothyroxine tablets

• The hormone (levothyroxine sodium) is lab‑synthesized. This active ingredient is not from pork. ^[3]
• However, some tablet formulations list excipients such as gelatin (unspecified), mannitol, maltodextrin, microcrystalline cellulose, croscarmellose sodium, and others. “Gelatin (unspecified)” indicates animal origin but does not state whether it is bovine or porcine. ^{[3] [6]}
• Example tablet listing: one levothyroxine tablet labeling includes gelatin among inactive ingredients. ^[3]
• Another common brand’s label shows gelatin (unspecified) as an inactive ingredient along with mannitol and corn starch. ^[4]

Levothyroxine soft gel capsules

• Many soft gel capsule products use a gelatin shell with glycerin and water. The gelatin source is not specified on labeling and may be animal‑derived (often bovine or porcine). ^{[5] [7]}

Desiccated thyroid (natural thyroid)

• Products such as NP Thyroid are derived from porcine thyroid glands and deliver both T4 (levothyroxine) and T3 (liothyronine). These are not appropriate for anyone avoiding pork due to allergy or religious dietary rules. ^{[1] [2]}

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Practical guidance for pork allergy or religious restrictions

• Avoid desiccated thyroid products (e.g., NP Thyroid), because they are made from pig thyroid. ^{[1] [2]}
• Check the specific levothyroxine product label (tablet vs capsule, and the manufacturer) for excipients. If “gelatin (unspecified)” is listed, there is a possibility it is animal‑derived, and clarification from the manufacturer or pharmacist may be needed. ^{[3] [4] [5]}
• Prefer tablet formulations without gelatin when possible. Some levothyroxine tablet labels list excipients but do not always include gelatin; however, several do list gelatin, so brand‑ and strength‑specific review is essential. ^{[3] [6]}
• Capsules commonly contain gelatin shells, so users with strict avoidance should consider tablet formulations that do not contain gelatin or consider non‑capsule liquid options if available in their market. ^[5]
• For individuals with severe pork allergy, while the active drug is synthetic, the risk would primarily relate to excipients (e.g., gelatin in some tablets/capsules). Verify the exact product’s excipient list and, if unclear, consult the manufacturer for the gelatin source; a pharmacist can help source a gelatin‑free formulation. ^{[3] [4] [5]}

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Example excipients by dosage form

• Levothyroxine tablets (example listing): butylated hydroxyanisole, colloidal silicon dioxide, croscarmellose sodium, gelatin, maltodextrin, mannitol, microcrystalline cellulose, povidone, sodium stearyl fumarate. ^{[3] [6]}
• Levothyroxine tablets (another brand example): mannitol, corn starch, gelatin (unspecified), croscarmellose sodium (varies by strength); confirm per strength. ^[4]
• Levothyroxine soft gel capsules: gelatin (unspecified), glycerin, water. ^{[5] [7]}
• Desiccated thyroid (NP Thyroid): active is porcine‑derived thyroid; inactive ingredients include calcium stearate, dextrose, maltodextrin/mineral oil depending on labeling. ^{[1] [2]}

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Is any dosage caution needed?

• Dose selection for levothyroxine is not altered by pork allergy or religious dietary rules, because the active drug is synthetic T4 and dosing is guided by clinical factors like TSH and body weight. ^[3]
• The key consideration is product selection (excipient profile) rather than dose. Choose a formulation that aligns with dietary/religious needs (e.g., gelatin‑free tablets) and then titrate dose as usual based on thyroid labs. ^{[3] [4]}
• Desiccated thyroid should be avoided if pork is contraindicated; if switching from desiccated thyroid to synthetic levothyroxine, dosing conversion and monitoring are needed, but this is routine endocrine practice rather than a pork‑specific dose precaution. ^{[1] [2]}

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Quick comparison table

Product type	Pork-derived content	Typical excipients of concern	Suitability for pork allergy/religious restriction
Levothyroxine tablet (synthetic)	Active is not pork-derived	May include gelatin (unspecified) in some brands/strengths	Generally suitable if a gelatin‑free tablet is selected; verify labeling
Levothyroxine soft gel capsule	Active is not pork-derived	Gelatin shell (unspecified animal source)	Use with caution; often not suitable unless manufacturer confirms non‑porcine or offers certified alternative
Desiccated thyroid (e.g., NP Thyroid)	Yes – porcine thyroid glands	Various non‑active excipients	Not suitable for pork avoidance

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Bottom line

• Levothyroxine itself is synthetic and not pork‑derived, but some formulations contain gelatin that may come from animals; labeling often lists “gelatin (unspecified)” without stating the species. ^{[3] [4] [5]}
• Desiccated thyroid products are porcine‑derived and should be avoided by those with pork allergy or religious restrictions. ^{[1] [2]}
• No special dosing precautions are required because of pork avoidance; instead, select a formulation whose excipients fit your needs (e.g., a gelatin‑free tablet) and dose according to thyroid function tests. ^{[3] [4]}

If you need help identifying a gelatin‑free levothyroxine tablet available in your region, your pharmacist can review specific manufacturers and strengths and contact the company to confirm gelatin source when “unspecified” is listed.