NutriStack
Levothyroxine and Zinc, timing-sensitive.
Zinc supplements may reduce levothyroxine absorption through chelation in the gastrointestinal tract. While the evidence is less robust than for calcium or iron, divalent cations like zinc are known to interact with thyroid hormones and the interaction is clinically plausible.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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At a glance
- Substances
- Levothyroxine and Zinc
- Pair type
- Timing Sensitive
- Evidence (highest tier)
- Emerging
- Source citations
- 5 sources
- Stack Score effect
- −5 to your Stack Score (per scored timing-sensitive row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Timing Sensitive · Emerging evidence
Timing Sensitive
What is happening. Zinc supplements may reduce levothyroxine absorption through chelation in the gastrointestinal tract. While the evidence is less robust than for calcium or iron, divalent cations like zinc are known to interact with thyroid hormones and the interaction is clinically plausible.
Mechanism. Zinc, as a divalent cation, can form chelate complexes with levothyroxine's phenolic and carboxylic acid groups, reducing its solubility and absorption across the intestinal mucosa.
Recommendation. Separate levothyroxine and zinc supplements by at least 4 hours as a precaution. Take levothyroxine first thing in the morning on an empty stomach.
Minimum separation. 240
Sources (5)
- Liwanpo L, Hershman JM. Conditions and drugs interfering with thyroxine absorption. Best Pract Res Clin Endocrinol Metab. 2009;23(6):781-792. PMID 19942153
- Ross DS. Treating hypothyroidism is not always easy: When to treat subclinical hypothyroidism, TSH goals in the elderly, and alternatives to levothyroxine monotherapy. Journal of Internal Medicine. 2022. PMID 34766382
- Hsu TJ, Hsieh RH, Huang CH et al.. Efficacy of Zinc Supplementation in the Management of Primary Dysmenorrhea: A Systematic Review and Meta-Analysis.. Nutrients. 2024. PMID 39683510
- Ali AA, Naqvi SK, Hasnain Z et al.. Zinc supplementation for acute and persistent watery diarrhoea in children: A systematic review and meta-analysis.. Journal of Global Health. 2024. PMID 39641338
- Oh C, Keats EC, Bhutta ZA. Vitamin and Mineral Supplementation During Pregnancy on Maternal, Birth, Child Health and Development Outcomes in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis.. Nutrients. 2020. PMID 32075071
Stack Score
How this pair moves the number.
Effect on the composite score
If both Levothyroxine and Zinc are in the same stack, this pair applies −5 to your Stack Score (per scored timing-sensitive row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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