NutriStack
Iron and Levodopa/Carbidopa, timing-sensitive.
Iron chelates levodopa in the GI tract, forming insoluble complexes that significantly reduce levodopa absorption. This can worsen Parkinson's disease symptoms by reducing the amount of levodopa reaching the brain. Studies show iron can reduce levodopa bioavailability by up to 50%.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Iron and Levodopa/Carbidopa
- Pair type
- Timing Sensitive
- Evidence (highest tier)
- Strong
- 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 · Strong evidence
Timing Sensitive
What is happening. Iron chelates levodopa in the GI tract, forming insoluble complexes that significantly reduce levodopa absorption. This can worsen Parkinson's disease symptoms by reducing the amount of levodopa reaching the brain. Studies show iron can reduce levodopa bioavailability by up to 50%.
Mechanism. Iron (Fe2+ and Fe3+) chelates levodopa through its catechol (dihydroxyphenyl) group, forming stable iron-levodopa complexes that are not absorbed in the intestine. Carbidopa does not prevent this chelation interaction.
Recommendation. Separate levodopa/carbidopa and iron supplements by at least 2 hours. Take iron at a different time of day than your Parkinson's medication. Inform your neurologist about iron supplementation.
Minimum separation. 120
Sources (5)
- Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31(3):251-255. PMID 2054263
- Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2023. PMID 36728680
- Rehman T, Agrawal R, Ahamed F et al.. Optimal dose and duration of iron supplementation for treating iron deficiency anaemia in children and adolescents: A systematic review and meta-analysis. PLoS One. 2025. PMID 39951396
- Gutema BT, Sorrie MB, Megersa ND et al.. Effects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis. PLoS One. 2023. PMID 37368919
- Hansen R, Sejer EPF, Holm C, Schroll JB. Iron supplements in pregnant women with normal iron status: A systematic review and meta-analysis. Acta Obstetricia et Gynecologica Scandinavica. 2023. PMID 37403900
Stack Score
How this pair moves the number.
Effect on the composite score
If both Iron and Levodopa/Carbidopa 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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