Recommended Dose for Multivitamin with Iron
For generally healthy adults, a standard multivitamin containing 14-18 mg of elemental iron taken once daily is appropriate, though this dose is insufficient for treating iron deficiency anemia. 1, 2
Standard Multivitamin Iron Content
- Most commercially available multivitamins contain approximately 14 mg of elemental iron per daily dose, which represents about 100% of the Recommended Dietary Allowance (RDA) for non-menstruating adults 2
- The FDA-approved labeling for standard iron-containing multivitamins recommends one tablet daily for adults and children 12 years and over 1
- These preparations typically contain ferrous iron (approximately 90% of formulations) and are often fortified with vitamin C at a median dose of 80 mg to enhance absorption 2
Important Context: When Standard Multivitamins Are Inadequate
The iron content in standard multivitamins (14-18 mg) falls well below therapeutic doses needed for treating iron deficiency or preventing deficiency in high-risk populations. 2
For Iron Deficiency Treatment
- Therapeutic iron supplementation requires 50-100 mg of elemental iron daily, which is 3-7 times higher than what standard multivitamins provide 3, 4, 5
- Women of childbearing age or those at increased risk of anemia should consume 50-100 mg elemental iron daily, not the 14 mg found in typical multivitamins 6
For Specific Populations Requiring Higher Doses
- Post-bariatric surgery patients: Require 45-60 mg elemental iron daily from dedicated supplements, not multivitamins alone 6
- Patients with inflammatory bowel disease: Should take no more than 100 mg elemental iron daily when disease is inactive, and avoid oral iron entirely during active disease 6
- Older adults: Most meet iron requirements through diet (average 10.8 mg/day from food), and routine iron supplementation beyond a standard multivitamin is generally unnecessary unless deficiency is documented 6
Optimal Timing and Administration
- Take the multivitamin in the morning on an empty stomach to maximize iron absorption 7, 8
- Avoid taking with tea, coffee, or calcium-rich foods, as these significantly reduce iron absorption by 54-66% 8
- If the multivitamin contains vitamin C (which most do at ~80 mg), this enhances iron absorption by approximately 30% 8, 9
- Do not take within 2 hours of calcium supplements or antacids, as these impair iron absorption 7
Common Pitfalls to Avoid
- Do not rely on multivitamins as the sole source of iron for treating diagnosed iron deficiency anemia - the 14 mg dose is inadequate and will delay appropriate treatment 4, 5
- Do not take multiple doses per day thinking this will increase absorption - once-daily dosing is optimal, as iron stimulates hepcidin elevation that blocks subsequent absorption for 24 hours 10, 8
- Do not assume all multivitamins are equivalent - verify the elemental iron content on the label, as formulations vary 2
When to Consider Dedicated Iron Supplements Instead
- If you have documented iron deficiency anemia (hemoglobin <12 g/dL in women, <13 g/dL in men), you need 50-100 mg elemental iron daily from a dedicated supplement, not a multivitamin 3, 4
- If you are pregnant, menstruating heavily, or have conditions affecting iron absorption, standard multivitamins provide insufficient iron 6, 2
- If you experience gastrointestinal side effects from higher-dose iron supplements, a standard multivitamin with 14-18 mg iron may be appropriate for maintenance after iron stores are repleted 2