Venofer Does Not Lower Vitamin B12 Levels
No evidence exists that Venofer (iron sucrose) IV infusions lower vitamin B12 levels. In fact, the relationship between iron and B12 appears to work in the opposite direction—iron deficiency itself may be associated with lower B12 levels that normalize with iron repletion.
The Actual Relationship Between Iron and Vitamin B12
Iron Deficiency May Lower B12 Levels
- Iron deficiency anemia is associated with significantly lower serum vitamin B12 levels compared to normal subjects, with some studies showing 45% of iron-deficient patients having B12 levels below 350 pg/mL 1
- Treatment of iron deficiency with oral iron supplementation significantly increases both serum vitamin B12 and folate levels, including normalization of B12 in patients who started with levels ≤200 pmol/L 2
- In patients with pernicious anemia who develop iron deficiency, those with iron deficiency actually had higher plasma B12 levels and lower homocysteine levels compared to iron-replete patients, suggesting complex metabolic interactions 3
Clinical Guidelines Address Vitamin Assessment Before Iron Therapy
- Guidelines recommend checking vitamin B12 and folate levels before initiating erythropoiesis-stimulating agents (ESAs) or iron therapy in anemic patients, primarily to exclude pre-existing vitamin deficiencies that could impair response to treatment 4
- Vitamin deficiency should be corrected prior to treating patients with ESAs, with folate 1-5 mg PO daily for 3 months if deficient, and vitamin B12 2000 mcg PO daily for 3 months if deficient 4
- This recommendation exists to optimize treatment response, not because iron therapy depletes vitamins 4
Venofer Safety Profile
Well-Established Safety Without B12 Concerns
- Iron sucrose (Venofer) has a well-established safety profile with relatively few serious adverse effects compared to other IV iron preparations, with no documented impact on vitamin levels 5, 6
- The documented adverse effects of Venofer include hypotension, flushing, abdominal cramps, and arthralgias/myalgias—not vitamin depletion 4, 5
- Venofer has been used clinically since 1949 with 70 years of accumulated safety data showing no association with B12 deficiency 6
Specific Dosing and Monitoring
- Maximum single dose is 200 mg, with maximum weekly dose of 500 mg 5
- No test dose is required for iron sucrose, though monitoring during infusion is recommended 4, 5
- Post-gastrectomy patients requiring both iron and B12 supplementation should receive them as separate interventions for their respective deficiencies, not because one causes depletion of the other 4
Clinical Bottom Line
The concern about Venofer lowering B12 is unfounded. If anything, correcting iron deficiency may help normalize B12 metabolism. Check B12 levels before starting iron therapy to identify pre-existing deficiencies that need concurrent treatment, not because iron will lower B12 4. Any patient with documented B12 deficiency requires appropriate B12 supplementation regardless of iron status 4.