Ferrous Fumarate with Vitamin C for Iron Deficiency Anemia
For iron deficiency anemia, take 210 mg ferrous fumarate once or twice daily (depending on menstrual status) with vitamin C to enhance absorption, separating it from calcium supplements by 1-2 hours. 1
Dosing Recommendations
Standard Dosing
- Non-menstruating adults: 210 mg ferrous fumarate once daily 1
- Menstruating women: 210 mg ferrous fumarate twice daily (providing 50-100 mg elemental iron daily) 1
- Continue iron supplementation for 3 months after correction of iron deficiency to replenish stores 1
Vitamin C Co-Administration
- Take iron with citrus fruits/drinks or vitamin C to enhance absorption 1, 2
- The American Gastroenterological Association recommends adding vitamin C as a Best Practice Advice, recognizing it as the most potent enhancer of non-heme iron absorption 2
- Practical options include taking iron with orange juice or 250-500 mg ascorbic acid 1, 2
- Vitamin C is particularly critical for plant-based diets where non-heme iron predominates 2
Timing and Administration Strategy
Optimal Timing
- Take iron once daily in the morning when hepcidin levels (which inhibit iron absorption) are lowest 2
- Consider every-other-day dosing as an alternative, which may be equally effective with better tolerability 2
- Take on an empty stomach for maximum absorption, though this must be balanced against tolerability 2
Critical Spacing Requirements
- Separate iron and calcium by 1-2 hours as calcium inhibits iron absorption 1
- Avoid tea and coffee within 1 hour of iron intake (coffee decreases absorption by 54%) 2
- Avoid taking with fiber-rich foods or dairy products 2, 3
Managing Side Effects
If gastrointestinal side effects are intolerable:
- Take iron with small amounts of food (accepting reduced absorption for improved adherence) 2, 3
- Start with lower doses and gradually increase to target 3
- Try taking iron at bedtime 3
- Consider alternative formulations like ferrous gluconate or iron bisglycinate 1, 2, 3
Evidence Quality Considerations
The 2020 British Obesity and Metabolic Surgery Society guidelines provide the most recent high-quality recommendations for ferrous fumarate dosing 1. While a 2023 meta-analysis found no statistically significant benefit of vitamin C co-administration 4, this contradicts established mechanistic understanding and multiple guideline recommendations 1, 2. The meta-analysis had very low quality evidence and included only 9 studies 4. In contrast, vitamin C's role as the most potent enhancer of non-heme iron absorption is well-established 2, 5, and a 2004 Taiwanese study demonstrated superior efficacy of ferrous fumarate combined with ascorbic acid 6.
Critical Contraindication
Patients with hemochromatosis or iron overload must completely avoid vitamin C supplements, as vitamin C accelerates iron mobilization and can cause cardiac complications including sudden death 2. If vitamin C is required for other medical reasons in iron-loaded patients, limit to 500 mg daily only after physician discussion 2.