What vitamin deficiency causes low hematocrit?

November 21, 2025 •

3 min read

According to the World Health Organization, anemia affects over 30% of the global population. A key contributing factor to this condition is nutritional deficiency, and understanding what vitamin deficiency causes low hematocrit is critical for proper diagnosis and treatment.

Quick Summary

Vitamin deficiencies, especially those involving vitamin B12, folate, and iron, impair the body's production of healthy red blood cells, resulting in a low hematocrit level.

Key Points

Low Hematocrit Causes: The primary vitamin deficiencies that cause low hematocrit are deficiencies in vitamin B12, folate (B9), and iron.
Megaloblastic Anemia: Both vitamin B12 and folate deficiencies lead to megaloblastic anemia, which is characterized by the production of abnormally large red blood cells that don't function properly.
Iron Deficiency Anemia: The most common type of anemia is caused by iron deficiency, leading to smaller, paler red blood cells (microcytic anemia) due to insufficient hemoglobin.
Pernicious Anemia: A specific cause of vitamin B12 deficiency is pernicious anemia, an autoimmune disorder that prevents the absorption of B12.
Symptom Awareness: Symptoms like fatigue, pale skin, shortness of breath, and neurological issues (with B12 deficiency) can indicate low hematocrit and anemia.
Dietary Prevention: Eating a balanced diet rich in iron, B12 (especially for vegans), and folate can help prevent nutritional anemias.
Importance of Diagnosis: Blood tests are necessary to diagnose the specific type of deficiency and guide the appropriate treatment, which may include supplements or injections.

Understanding Hematocrit and Anemia

Hematocrit is the percentage of your blood volume that is occupied by red blood cells (RBCs). These cells are essential for carrying oxygen from the lungs to the rest of the body. A low hematocrit level indicates a reduced number of red blood cells, a condition known as anemia. Anemia can arise from many factors, but nutritional deficiencies, particularly specific vitamin deficiencies, are a common cause.

When the body lacks vital nutrients, it cannot produce healthy, functional red blood cells, leading to a decreased overall volume of RBCs, which is reflected in a low hematocrit test result. The type of anemia and characteristics of red blood cells produced depend on the deficient vitamin.

Key Vitamin Deficiencies that Cause Low Hematocrit

Several vitamin deficiencies disrupt red blood cell production in bone marrow, leading to low hematocrit.

Vitamin B12 Deficiency (Megaloblastic Anemia)

Vitamin B12 is vital for DNA synthesis and RBC maturation. Deficiency results in the production of abnormally large, immature cells (megaloblasts) instead of healthy, mature ones, leading to low hematocrit.

Key causes include pernicious anemia (an autoimmune condition affecting B12 absorption), dietary factors (common in vegans without supplements), absorption issues (like Crohn's or celiac disease), and the effects of alcoholism or certain medications.

Folate (Vitamin B9) Deficiency (Megaloblastic Anemia)

Folate assists vitamin B12 in healthy RBC formation. Like B12 deficiency, folate deficiency causes megaloblastic anemia, where oversized, poorly developed red blood cells are produced, lowering healthy RBC count and hematocrit.

Causes include a poor diet lacking folate-rich foods, increased demand (e.g., during pregnancy), and malabsorption from digestive issues.

Iron Deficiency Anemia (Microcytic Anemia)

Iron is needed to make hemoglobin, the oxygen-carrying protein in RBCs. Low iron means insufficient hemoglobin, resulting in small, pale red blood cells (microcytic anemia). Iron deficiency is the most common global cause of low hematocrit and anemia.

Common causes are chronic blood loss (heavy periods, internal bleeding), diets low in iron, poor absorption (celiac disease), and indirectly, vitamin C deficiency which impairs iron absorption.

Comparison of Deficiency Anemias


Feature	Vitamin B12 Deficiency	Folate Deficiency	Iron Deficiency
Anemia Type	Megaloblastic	Megaloblastic	Microcytic
Red Blood Cell Size	Abnormally large	Abnormally large	Abnormally small
Key Functions	DNA synthesis, nervous system health	DNA synthesis, cell growth	Hemoglobin production
Common Causes	Pernicious anemia, vegan diet, malabsorption, alcoholism	Poor diet, pregnancy, malabsorption	Blood loss, poor diet, malabsorption
Distinct Symptoms	Neurological issues (tingling, numbness), memory problems	Sore tongue, diarrhea (no neurological issues like B12)	Pica (cravings for ice), brittle nails, weakness
Treatment	B12 injections or high-dose oral supplements	Folic acid tablets for several months	Iron supplements, dietary changes

Less Common but Important Vitamin Deficiencies

Beyond B12, folate, and iron, other vitamins can affect hematocrit:

Vitamin B6: Deficiency can lead to anemia and low hematocrit.
Vitamin E: In premature infants, deficiency can cause hemolytic anemia, where RBCs are destroyed rapidly.

Diagnosis and Treatment

Symptoms of anemia prompt a doctor to order blood tests like a complete blood count (CBC) to check hematocrit, RBC size, and shape, helping identify the cause. Further tests measure specific vitamin levels.

Treatment targets the underlying deficiency and its severity:

Oral Supplements: For deficiencies due to diet or mild malabsorption.
Injections: Often needed for severe B12 deficiency or absorption issues like pernicious anemia.
Dietary Changes: Increasing vitamin-rich foods is vital for long-term management.

Conclusion

A low hematocrit level often indicates anemia caused by deficiencies in essential vitamins, primarily B12, folate, and iron. These deficiencies hinder the body's ability to produce healthy red blood cells, with each resulting in a distinct type of anemia. Early diagnosis through blood tests and targeted treatment, including supplements and diet adjustments, are crucial. For more information on anemia, consult resources like the World Health Organization (WHO) website WHO website.

Frequently Asked Questions

The most common nutritional deficiency leading to low hematocrit and anemia is iron deficiency.

Yes, a deficiency in vitamin B12 can cause megaloblastic anemia, which results in a low hematocrit due to the body producing fewer, abnormally large red blood cells.

Folate deficiency prevents the bone marrow from creating healthy, mature red blood cells, leading to oversized and fewer cells, a condition called megaloblastic anemia.

Initial symptoms can be subtle and include fatigue, weakness, pale skin, and shortness of breath. Symptoms worsen as the deficiency becomes more severe.

Yes, pernicious anemia is a specific type of vitamin B12 deficiency caused by an autoimmune condition that prevents the absorption of B12 from the diet.

Diagnosis involves blood tests, including a complete blood count (CBC) to measure hematocrit and red blood cell size, as well as tests to measure specific vitamin levels.

Yes, for many cases, increasing the intake of the missing vitamin through diet and supplements can effectively treat and reverse the low hematocrit, although some individuals may require injections.