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Head-to-head evidence comparison — which supplement is right for you?
Iron vs Multivitamin: Iron has the stronger overall evidence (9 vs 6/10); take care combining them — there's a flagged interaction. Take the 60-second quiz for a pick tailored to your goals.
Iron wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
6 of 8 studies with measurable effects showed benefit.
Top outcomes
Verdict
Too few graded studies
Top outcomes
Shared outcomes (1)
Outcomes where both Iron and Multivitamin have evidence — compare verdict strength side-by-side.
18-40mg elemental iron for deficiency (varies by severity) (a typical label dose, not the dose used in the cited trials, which used 60 to 120 mg a day)
On empty stomach if tolerated, Away from tea, coffee, dairy
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
1 serving daily (as directed on label, typically 1-2 tablets/capsules)
With breakfast, With lunch (if GI sensitive)
Capsule or softgel
and 6 more not shown
and 7 more not shown
If the multivitamin contains iron, taking both long term can lead to iron accumulation in people who are not iron deficient, particularly men, post-menopausal women and people with hereditary haemochromatosis. Iron taken at the same time also competes with the multivitamin's zinc and copper for absorption.
Check whether the multivitamin contains iron. If it does, add an iron supplement only for a confirmed deficiency (ferritin and transferrin saturation) and count the iron from both. If it does not, the pair does not duplicate iron. Taking the iron at a different time from the multivitamin reduces competition with its other minerals.
2-4 weeks
4-8 weeks
4-12 weeks
3-6 months
4-8 weeks
2-6 weeks
6-12 weeks
Daily oral iron supplementation during pregnancy
The Cochrane database of systematic reviews (2024) · Meta analysis · n=48971
There is probably little to no difference in maternal death (2 versus 4 events, RR 0.57, 95% CI 0.12 to 2.69; 3 trials, 14,060 women; moderate-certainty evidence).
The Prevalence of Anemia among Pregnant Women in China: A Systematic Review and Meta-Analysis
Nutrients (2024) · Meta analysis · n=1376204
The results showed that the prevalence of anemia, ID, and IDA among pregnant women in China were 30.7% (95% CI: 26.6%, 34.7%), 45.6% (95% CI: 37.0%, 54.2%), and 17.3% (95% CI: 13.9%, 20.7%), respectively.
Treatment for women with postpartum iron deficiency anaemia
The Cochrane database of systematic reviews (2024) · Meta analysis · n=4558
Intravenous iron versus oral iron supplementation The evidence is very uncertain about the effect of intravenous iron on mortality (risk ratio (RR) 2.95, 95% confidence interval (CI) 0.12 to 71.96; P = 0.51; I² = not applicable; 3 RCTs; 1 event; 572 women; very low-certainty evidence).
Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS
The American Journal of Clinical Nutrition (2024) · Meta analysis · n=5203
Pooled 5,203 non-overlapping participants from three cognitive substudies of the COSMOS trial of US adults aged 60 or older: COSMOS-Clinic (573), COSMOS-Mind (2,158) and COSMOS-Web (2,472).
Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial
Alzheimer's & Dementia (2023) · Rct · n=2262
COSMOS-Mind: 2,262 older adults (mean age 73, 60% women) randomised in a 2x2 factorial design to cocoa extract and to a commercial multivitamin-mineral, each versus placebo, for 3 years, with cognition tested by telephone.
Long-term multivitamin supplementation and cognitive function in men: a randomized trial
Annals of Internal Medicine (2013) · Rct · n=5947
5,947 male physicians aged 65 or older in the Physicians' Health Study II, randomised to a daily multivitamin or placebo, with up to 4 telephone cognitive assessments over 12 years.
Iron has a higher evidence score (9/10 vs 6/10) and wins in 2 of 3 categories.
For boost daily energy, Iron has a higher relevance score (90 vs 75).
Caution: If the multivitamin contains iron, taking both long term can lead to iron accumulation in people who are not iron deficient, particularly men, post-menopausal women and people with hereditary haemochromatosis. Iron taken at the same time also competes with the multivitamin's zinc and copper for absorption. Check whether the multivitamin contains iron. If it does, add an iron supplement only for a confirmed deficiency (ferritin and transferrin saturation) and count the iron from both. If it does not, the pair does not duplicate iron. Taking the iron at a different time from the multivitamin reduces competition with its other minerals. Always consult a healthcare provider before combining these supplements.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.