Can Low Vitamin D Affect Blood? Understanding the Hematological Impact

December 26, 2025 •

4 min read

Affecting nearly one billion people globally, vitamin D deficiency is a widespread health concern, but its impact extends beyond bone health. This article explores the significant and sometimes surprising ways can low vitamin D affect blood, revealing connections to red blood cell production, blood pressure, and clotting processes.

Quick Summary

Low vitamin D can influence blood health by affecting red blood cell production via the hormone hepcidin, impacting blood pressure regulation, and potentially influencing blood clotting and platelet function.

Key Points

Anemia Association: Low vitamin D levels are correlated with a higher risk of anemia, particularly the 'anemia of inflammation,' by increasing the iron-regulating hormone hepcidin.
Red Blood Cell Production: Vitamin D plays a role in supporting erythropoiesis by promoting the growth of red blood cell progenitor cells in the bone marrow.
Blood Pressure Control: A vitamin D deficiency can impact blood pressure by disrupting the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance.
Clotting and Platelets: Low vitamin D levels have been linked to higher platelet counts and may affect the balance of pro- and anti-coagulation factors, potentially influencing the risk of blood clots.
Bone Marrow Health: Vitamin D receptors in bone marrow indicate a direct role in blood cell production, and severe deficiency has been associated with conditions affecting marrow function, like myelofibrosis.
Overall Hematological Function: Maintaining adequate vitamin D levels is important for supporting overall blood health, including circulation, oxygen transport, and immune cell function.

Vitamin D is a fat-soluble nutrient well-known for its crucial role in maintaining strong bones by facilitating calcium absorption. However, emerging research shows that its influence is far more extensive, reaching into the complex world of hematology. A deficiency can disturb the delicate balance of blood health, from the production of red blood cells to the regulation of clotting.

The Indirect Link Between Vitamin D and Anemia

Anemia, a condition defined by a low red blood cell count, often has many root causes. While iron deficiency is the most common cause, low vitamin D levels have been found to be an associated risk factor. The connection is indirect but biologically significant and involves several pathways.

The Role of Hepcidin

One of the most important links involves the hormone hepcidin, which regulates the amount of iron available in the body for red blood cell production.

High Hepcidin: When inflammation is present, hepcidin levels rise. High hepcidin blocks iron absorption from the gut and traps iron in storage cells, preventing it from being used to make new red blood cells.
Low Vitamin D's Influence: Research shows that low vitamin D levels can trigger an increase in hepcidin levels. Correcting a vitamin D deficiency may help lower hepcidin, freeing up iron for red blood cell production, particularly in cases of 'anemia of inflammation'.

Support for Erythropoiesis

Beyond its effect on iron availability, vitamin D may also directly support erythropoiesis, the process of red blood cell creation. Studies have shown that vitamin D can promote the growth and proliferation of progenitor cells in the bone marrow that produce red blood cells. Vitamin D receptors (VDR) are found in bone marrow cells, and adequate levels are thought to be important for proper blood cell development.

Vitamin D's Impact on Blood Pressure

High blood pressure (hypertension) is a major risk factor for cardiovascular disease. While the relationship is complex and not fully understood, numerous studies have shown an association between low vitamin D levels and an increased risk of hypertension.

One of the key mechanisms involves the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. Vitamin D has been shown to suppress the expression of renin, a hormone that initiates the RAAS cascade. In deficient states, this suppressive effect is weakened, potentially leading to RAAS overactivity and higher blood pressure. Additionally, vitamin D's anti-inflammatory properties may help protect the lining of blood vessels (the endothelium), which is crucial for regulating blood pressure.

Blood Clotting and Coagulation

The body's ability to form clots (coagulation) is a crucial process, but unwanted or excessive clotting can lead to serious conditions like deep vein thrombosis (DVT), stroke, and heart attack. The link between low vitamin D and blood clotting is an active area of research, with some evidence suggesting a connection.

How Vitamin D Influences Coagulation

Platelet Function: Studies have shown an inverse correlation between vitamin D levels and platelet counts. Lower vitamin D has been linked to higher platelet counts, which could increase the risk of thrombotic events.
Anticoagulant Effects: Vitamin D may influence the balance between pro- and anti-clotting factors. Some research suggests it can increase the production of thrombomodulin (an anticoagulant protein) while decreasing tissue factor (a pro-coagulant protein).
Inflammation: As with anemia, vitamin D's anti-inflammatory action plays a role. Chronic inflammation can create a pro-coagulant environment, and a deficiency may exacerbate this.

Comparison of Hematological Effects


Blood Component	Affected by Low Vitamin D	Mechanism and Consequences
Red Blood Cells	Yes	Low vitamin D increases hepcidin, which limits iron for erythropoiesis. May also directly impair red blood cell production in bone marrow. Result can be anemia.
Blood Pressure	Yes	Low vitamin D is linked to increased activity of the renin-angiotensin system, which can raise blood pressure. May also contribute to endothelial dysfunction.
Platelets	Yes	Inverse correlation observed; low vitamin D linked to higher platelet counts. Influences proteins involved in clot formation. Result can be increased risk of thrombosis.
Immune Cells in Marrow	Yes	Animal studies indicate vitamin D receptor signaling in macrophages can stimulate bone marrow fibrosis, disrupting normal blood cell production.

Potential Effects on Bone Marrow

Bone marrow is the spongy tissue inside bones where all blood cells are produced. The presence of vitamin D receptors in the bone marrow suggests a direct role in this process. In rare cases, severe vitamin D deficiency has been associated with myelofibrosis in children, a condition involving bone marrow scarring that disrupts normal blood cell production. Although such occurrences are extremely rare, the link highlights the foundational importance of this vitamin for hematopoiesis. Animal studies have also demonstrated a clear role for vitamin D receptor signaling in immune cells within the bone marrow, showing that its modulation can impact conditions that affect blood cell production.

Conclusion: The Broader View of Vitamin D

The question, "Can low vitamin D affect blood?" has a clear answer: yes. While its most famous role is in bone health, vitamin D's influence on the blood is undeniable and multifaceted. It impacts the availability of iron for red blood cell production by regulating hepcidin, affects blood pressure by modulating the RAAS, and plays a role in the complex system of blood clotting and platelet regulation. For individuals with blood-related issues like unexplained anemia, hypertension, or a history of thrombotic events, assessing vitamin D levels could be a valuable diagnostic step. Maintaining adequate vitamin D, through sun exposure, diet, or supplementation, is a simple but powerful strategy for supporting overall health, including the often-overlooked health of your blood.

For more detailed information on vitamin D metabolism and function, please visit the NIH Office of Dietary Supplements.

Frequently Asked Questions

While low vitamin D can contribute to anemia, especially in inflammatory conditions, it is not usually the primary cause. Anemia is most commonly caused by iron or B12 deficiency, blood loss, or chronic diseases. However, correcting a vitamin D deficiency may improve coexisting anemia.

Common symptoms of a deficiency include fatigue, muscle weakness, and dizziness, which can overlap with signs of anemia caused by altered red blood cell function. High blood pressure is also associated with low vitamin D levels.

Yes, observational studies have found an inverse relationship, where people with lower vitamin D levels have a higher risk of developing high blood pressure. Vitamin D helps regulate the system that controls blood pressure.

Some studies suggest an association between low vitamin D and an increased risk of blood clots, particularly venous thromboembolism. Research shows vitamin D influences both pro-clotting and anti-clotting factors, but more research is needed to confirm the exact mechanisms.

For certain types of anemia, especially anemia of inflammation, vitamin D supplementation has shown promise in improving iron availability and hemoglobin levels by reducing hepcidin. However, it is not a sole treatment for most forms of anemia and is best used as an adjunct therapy.

Vitamin D receptors are present in bone marrow cells, suggesting a direct role in blood cell formation (hematopoiesis). It appears to stimulate the progenitor cells that develop into red blood cells, which can be impaired in severe deficiency.

While some research suggests vitamin D may have anticoagulant properties by affecting certain proteins involved in clotting, it is not a replacement for prescribed blood-thinning medication. Taking too much vitamin D can be harmful, so always follow medical advice regarding dosage.