Does taking vitamin D increase iron levels? Unpacking the Complex Connection

October 16, 2025 •

4 min read

Anemia is a major public health concern affecting billions worldwide, with iron deficiency being the primary cause in many cases. Coincidentally, vitamin D deficiency is also widespread, leading many to question if there is a relationship between these two micronutrients and, most importantly, does taking vitamin D increase iron levels? Research shows the connection is more nuanced than a simple cause-and-effect and varies significantly depending on an individual's underlying health status.

Quick Summary

This article explores the scientific relationship between vitamin D supplementation and iron levels, detailing how vitamin D may indirectly influence iron metabolism, particularly in cases of chronic inflammation. It examines findings from both observational and interventional studies to provide a comprehensive view of the evidence, highlighting why the answer is not a simple yes or no.

Key Points

Indirect Impact: Taking vitamin D does not directly increase iron levels in healthy people, but can indirectly influence iron availability through other metabolic pathways.
Mediated by Hepcidin: Vitamin D can suppress the production of hepcidin, a hormone that regulates iron absorption. This effect is most relevant in cases of inflammation.
Supports Anemia of Inflammation: The most promising evidence shows that vitamin D supplementation can improve iron status and hemoglobin levels in individuals with chronic diseases and associated inflammation.
Limited Effect in Healthy Individuals: Studies on healthy adults and adolescents often find no significant change in iron markers after vitamin D supplementation, suggesting it is not a cure for standard iron deficiency.
Reciprocal Relationship: Evidence suggests that low iron levels can also impair the body's ability to activate vitamin D, highlighting a bidirectional metabolic link.
Assess Both Deficiencies: In many at-risk populations, like pregnant women, both deficiencies coexist. It is important to assess and address both nutritional statuses for optimal health.

The Indirect Connection: Hepcidin and Inflammation

Research has shown that vitamin D can play a role in iron metabolism, but not by directly increasing iron levels in healthy individuals. Instead, its influence appears to be mediated through the regulation of a key hormone called hepcidin.

Hepcidin's Role: Hepcidin, produced in the liver, is the body's master regulator of iron. It controls how much iron is absorbed from the diet and released from cellular stores. High levels of hepcidin inhibit the release of iron, effectively locking it away and leading to a form of anemia, often called "anemia of inflammation".
Vitamin D's Influence: Studies have identified that active vitamin D can suppress the production of hepcidin. By lowering hepcidin levels, vitamin D can potentially improve iron bioavailability, making more iron available for the body to use for functions like red blood cell production.
Inflammation as a Driver: This mechanism is particularly relevant in cases where chronic inflammation is present, such as in chronic kidney disease. Inflammation triggers the body to produce more hepcidin, leading to poor iron status even if iron intake is sufficient. Vitamin D's anti-inflammatory properties may, in turn, help to reverse this process and improve iron availability.

Contrasting Research: Observational vs. Interventional Findings

The scientific literature presents a mixed picture regarding the direct impact of vitamin D supplementation on iron levels, largely depending on the type of study conducted and the health of the participants.

Observational Studies

Observational studies analyze existing data without direct intervention. Findings often show a positive correlation between higher vitamin D status and improved iron markers.

Correlations, Not Causation: A positive correlation does not mean causation. It may simply indicate that individuals with better overall nutritional status and health also have higher levels of both vitamin D and iron.
Examples: Several studies have found that individuals with vitamin D deficiency have a higher prevalence of anemia. However, these studies cannot definitively prove that a lack of vitamin D is the direct cause of the low iron levels.

Interventional Studies

Interventional studies, where participants are given vitamin D supplements, provide stronger evidence of a causal link. However, these studies have shown less conclusive results, especially in healthy individuals.

Limited Impact in Healthy Populations: A recent NHS Blood and Transplant study in healthy older adults found no significant changes in iron levels despite a significant increase in vitamin D levels from supplementation. A similar result was seen in a study of healthy Saudi adolescents, where vitamin D supplementation did not improve iron status.
Potential Benefit in Specific Conditions: In contrast, studies involving patients with chronic kidney disease and anemia have shown that vitamin D supplementation can lead to increased hemoglobin levels and a reduced need for erythropoiesis-stimulating agents. This highlights that the therapeutic effect is specific to certain disease states characterized by chronic inflammation.

The Two-Way Street: A Reciprocal Relationship

Emerging evidence suggests that the relationship between vitamin D and iron might be a two-way street.

Iron's Role in Vitamin D Metabolism: Some studies propose that iron is a cofactor for the enzymes that activate vitamin D in the body. Therefore, iron deficiency could potentially impair vitamin D metabolism and contribute to a deficiency.
Targeting Interventions: This reciprocal relationship emphasizes the importance of addressing both deficiencies concurrently when they co-exist, especially in vulnerable populations like pregnant women and malnourished children.

Factors influencing the vitamin D and iron relationship

Underlying Health Conditions: The presence of chronic inflammation or diseases like chronic kidney disease significantly alters how vitamin D influences iron status.
Inflammatory Markers: Elevated levels of inflammatory cytokines (like IL-6) can interfere with iron metabolism by upregulating hepcidin. Vitamin D's anti-inflammatory effects can indirectly counteract this.
Genetics and Ethnicity: Differences in genetic backgrounds and ethnicity may influence the effectiveness of vitamin D on iron status and anemia outcomes.
Baseline Deficiency Severity: The degree of vitamin D and iron deficiency at the start of supplementation can impact the results. Individuals with severe deficiencies may respond differently than those with mild insufficiency.

Summary of findings on vitamin D and iron interaction


Feature	Observational Studies	Interventional Studies (Healthy)	Interventional Studies (Inflammation)
Association Observed	Positive correlation between vitamin D levels and iron status (e.g., hemoglobin, ferritin).	No significant increase in iron markers or hemoglobin levels observed with vitamin D supplementation.	Can increase hemoglobin and reduce the need for stimulating agents.
Causality	Correlation, not causation. Often confounded by overall health and nutrition.	Suggests vitamin D supplementation alone does not directly increase iron levels.	Points to a causal effect, but limited to specific disease states.
Underlying Mechanism	Does not reveal the mechanism, only the relationship.	Shows that suppressing hepcidin does not translate to significant iron increases in non-inflammatory contexts.	Anti-inflammatory effects reduce hepcidin, restoring iron bioavailability.

Conclusion

While a direct causal link demonstrating that taking vitamin D increases iron levels has not been established in healthy individuals, a nuanced and significant association exists. The therapeutic benefits of vitamin D for iron status appear to be most pronounced in patients suffering from conditions characterized by chronic inflammation, such as chronic kidney disease. In these cases, vitamin D may help improve iron availability by suppressing the iron-regulating hormone hepcidin. For the general population, improving vitamin D status should not be viewed as a primary treatment for iron deficiency, which is best addressed through direct iron supplementation and dietary improvements. The best approach involves assessing and addressing both deficiencies, especially in at-risk populations like pregnant women.

Learn More

For deeper insights into the interplay between vitamin D and anemia, refer to the systematic review: Effects of Iron on Vitamin D Metabolism: A Systematic Review.

Frequently Asked Questions

No. While low vitamin D and anemia can coexist, taking vitamin D is not a substitute for iron supplementation to treat iron deficiency anemia. Iron deficiency requires direct iron intake to correct the deficit.

Inflammation causes the body to produce more hepcidin, a hormone that blocks iron release. Vitamin D has anti-inflammatory properties that can lower hepcidin, thereby improving iron availability, especially in chronic inflammatory conditions.

The discrepancy often lies in the type of study and the population. Observational studies may find a correlation because healthier people have better nutrition overall, while interventional trials show supplementation has little effect on iron in healthy individuals. The effects are most notable in populations with underlying chronic inflammation.

Hepcidin is a hormone that regulates iron metabolism. It reduces iron absorption from the gut and blocks its release from cellular stores. Vitamin D's ability to suppress hepcidin is the key mechanistic link between the two nutrients.

Yes. It is recommended to check for both vitamin D and iron deficiencies, as they often coexist in at-risk populations. A doctor can determine if concurrent supplementation is appropriate based on your specific health profile.

No, clinical trials have not shown a beneficial effect of iron supplementation on improving vitamin D status. The relationship may be bidirectional, but iron supplementation alone won't correct a vitamin D deficiency.

Yes, patients with anemia of inflammation, such as those with chronic kidney disease, are more likely to see an improvement in iron status from vitamin D supplementation.