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Head-to-head evidence comparison — which supplement is right for you?
Vitamin B12 wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Probably helps
9 of 13 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
12 of 17 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Iron and Vitamin B12 have evidence — compare verdict strength side-by-side.
18-45mg elemental iron for deficiency (varies by severity)
On empty stomach if tolerated, Away from tea, coffee, dairy
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
500-1000mcg daily for maintenance; higher for deficiency
Morning (may be energizing), With or without food
Methylcobalamin (sublingual)
2-4 weeks
4-8 weeks
4-12 weeks
2-4 weeks
4-8 weeks
Weeks to months
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=722
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=572
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).
Efficacy of different routes of vitamin B12 supplementation for the treatment of patients with vitamin B12 deficiency: A systematic review and network meta-analysis
Irish journal of medical science (2024) · Meta analysis · n=4275
Regarding the hemoglobin level, the pooled effect sizes showed no difference between all routes of administration that could reach statistical significance.
Dosage exploration of combined B-vitamin supplementation in stroke prevention: a meta-analysis and systematic review
The American journal of clinical nutrition (2024) · Meta analysis · n=76664
In areas without and with partial folic acid fortification, combined B-vitamin supplementation significantly reduced the risk of stroke by 34% [RR: 0.66; 95% confidence interval (CI): 0.50, 0.86] and 11% (RR: 0.89; 95% CI: 0.79, 1.00), respectively.
Vitamin Status in Patients with Phenylketonuria: A Systematic Review and Meta-Analysis
International journal of molecular sciences (2024) · Meta analysis · n=770
The effect sizes were expressed as standardised mean differences.
Based on meta-analyses showing hemoglobin improvements of 2.01-5.30 g/dL in iron deficient populations. Higher doses show diminishing returns with increased GI side effects. Effectiveness varies significantly by baseline iron status and form used.
AI-estimated from published studies. Interpret as directional guidance.
Vitamin B12 has a higher evidence score (9/10 vs 9/10) and wins in 1 of 3 categories.
For boost daily energy, Iron has a higher relevance score (90 vs 85).
No known interactions between Iron and Vitamin B12 have been documented in our database. However, always consult a healthcare provider before combining supplements.