Causes of High MCV Levels and How to Reduce Them Naturally

MCV (Mean Corpuscular Volume) reflects the average size of red blood cells. When this value is high, it tells us that red blood cells are larger than usual, a pattern known as macrocytosis. In routine lab and OPD practice, high MCV is less about an immediate emergency and more about a signal—it nudges the clinician to look for nutritional gaps, alcohol-related effects, liver or thyroid issues, or medication-related changes.

Many people with mildly raised MCV feel completely normal. Others may notice fatigue or vague symptoms that don’t clearly point to a cause. That is why MCV is always interpreted alongside hemoglobin, other CBC parameters, and the patient’s history. This article explains what high MCV means, why it happens, the symptoms that may be associated with it, practical lifestyle and dietary measures that support improvement, and when medical review becomes important.

Short Overview: What High MCV Means

High MCV means red blood cells are larger than normal. Clinically, this usually happens when red blood cell division or maturation is slowed. The most frequent contributors are vitamin B12 or folate deficiency, alcohol use, liver disease, thyroid dysfunction, or the effect of certain long-term medications.

In everyday practice, doctors often see high MCV as an early clue rather than a diagnosis by itself. In many cases, once the underlying issue is corrected, MCV gradually returns toward the normal range.

Medical Causes of High MCV Levels

High MCV develops when something interferes with normal red blood cell formation.

Vitamin B12 deficiency
This is one of the most common causes. Without enough B12, red blood cells fail to divide properly and become oversized. Clinically, this is often seen in people with restricted diets, absorption problems, autoimmune gastritis, or prolonged use of acid-suppressing medications.

Folate (vitamin B9) deficiency
Folate is essential for DNA synthesis in red blood cells. Low levels lead to large, immature cells. Alcohol use, poor dietary intake, pregnancy, digestive disorders, and some medications can contribute.

Alcohol use
Alcohol is a very frequent reason for raised MCV in routine lab reports. Even without clear vitamin deficiency, alcohol can directly alter bone marrow function and red blood cell maturation. This pattern is commonly noticed before liver enzymes become abnormal.

Liver disease
The liver plays an important role in nutrient handling and blood health. Fatty liver, hepatitis, or cirrhosis can all be associated with macrocytosis.

Hypothyroidism
Low thyroid hormone slows many body processes, including red blood cell production. In practice, unexplained high MCV sometimes improves once thyroid levels are corrected.

Bone marrow disorders
Less common but important causes include myelodysplastic syndromes or other marrow dysfunctions. These are usually considered when MCV is markedly high or associated with falling blood counts.

Medications
Certain drugs—such as chemotherapy agents, anti-seizure medicines, methotrexate, or long-term antiretroviral therapy—can increase MCV. In these cases, doctors usually monitor trends rather than reacting to a single value.

Dehydration Factors That Can Influence MCV

Dehydration does not truly enlarge red blood cells, but by reducing plasma volume it can accentuate abnormal values or make existing macrocytosis appear more pronounced. Poor fluid intake, excessive sweating, vomiting, diarrhea, or intense exercise without hydration can all contribute. Maintaining adequate hydration supports more reliable blood measurements.

Chronic Diseases Linked to High MCV

Several long-standing conditions can indirectly raise MCV by affecting absorption, metabolism, or bone marrow function:

Chronic liver disorders
Chronic kidney disease
Autoimmune or inflammatory bowel diseases that impair nutrient absorption
Long-standing hypothyroidism

In such patients, MCV is followed over time rather than judged in isolation.

Impact of Smoking and Alcohol on MCV

Smoking
Smoking mainly affects hemoglobin and oxygen delivery, but over time it can worsen nutritional deficiencies and overall blood quality, indirectly influencing MCV patterns.

Alcohol
Alcohol is one of the strongest contributors to high MCV. Clinically, MCV often starts falling within weeks of reducing or stopping alcohol intake, even before other blood tests normalize.

Symptoms of High MCV Levels

Many people with high MCV have no symptoms, especially when elevation is mild. When symptoms occur, they usually relate to the underlying cause rather than the MCV itself:

Fatigue or weakness
Pale or sometimes flushed skin
Shortness of breath on exertion
Dizziness or palpitations
Tingling, numbness, or memory issues (classically with B12 deficiency)

Neurological symptoms are particularly important to note, as they suggest significant B12 deficiency and should not be ignored.

How to Reduce High MCV Levels Naturally

Improving high MCV focuses on correcting the underlying imbalance rather than targeting the number alone.

Support vitamin B12 intake
Including reliable dietary sources such as eggs, dairy products, fish, poultry, and fortified foods helps maintain healthy red blood cell maturation.

Support folate intake
Leafy greens, legumes, citrus fruits, avocado, and whole foods naturally provide folate needed for normal RBC development.

Reduce or avoid alcohol
In routine practice, this is often the single most effective step. Even partial reduction can lead to measurable improvement in MCV over time.

Maintain good hydration
Adequate daily fluid intake helps stabilize blood volume and supports overall circulation.

Support liver and gut health
Balanced meals, limiting highly processed foods, and addressing digestive issues help nutrient absorption and blood health.

Balanced daily diet
Regular intake of protein, fruits, vegetables, and whole grains supports bone marrow function and red blood cell production.

When High MCV Levels Become Concerning

High MCV deserves closer evaluation when it is:

Persistently elevated on repeated tests
Associated with falling hemoglobin or other blood counts
Accompanied by neurological symptoms
Markedly high (often above ~110 fL)
Seen alongside liver disease, thyroid disease, or heavy alcohol use

In such cases, doctors usually investigate vitamin levels, liver function, thyroid status, medication history, and overall clinical context.

When to See a Doctor

Medical review is advised if:

MCV remains high over time
Fatigue, breathlessness, or neurological symptoms develop
There is known liver, thyroid, or gastrointestinal disease
Alcohol intake is regular or heavy
You are pregnant or have unexplained weight loss

Early evaluation helps prevent long-term complications.

Test Preparation for MCV Test

No fasting is required
Stay well hydrated
Avoid alcohol for at least 24 hours before testing
Inform the doctor about vitamin supplements and long-term medications
Mention thyroid or liver conditions if present

Important Word Explanations

MCV: Average size of red blood cells
Macrocytosis: Presence of larger-than-normal red blood cells
Folate: Vitamin B9, essential for red blood cell formation
Vitamin B12 deficiency: Lack of B12 affecting blood and nerve health
Bone marrow: Tissue where blood cells are produced

Causes of High MCV Levels and How to Reduce Them Naturally