What are the symptoms of high or low MCV?

October 1, 2025 •

3 min read

Approximately 3% of the general population may have macrocytosis, or high MCV, indicating larger-than-average red blood cells. Understanding what are the symptoms of high or low MCV is a crucial step in interpreting your blood test results and identifying potential underlying health issues.

Quick Summary

The symptoms of abnormal Mean Corpuscular Volume (MCV) levels often overlap, commonly presenting as fatigue, weakness, and shortness of breath due to inefficient oxygen transport. High MCV is often linked to vitamin B12 or folate deficiencies, while low MCV is typically associated with iron deficiency or chronic disease.

Key Points

Symptom Overlap: High and low MCV can both cause fatigue, weakness, shortness of breath, and pale skin, reflecting inadequate oxygen delivery.
High MCV Symptoms: Specific signs for high MCV (macrocytosis) include neurological issues like tingling or numbness, cognitive difficulties, and a smooth or swollen tongue, often linked to vitamin B12 or folate deficiency.
Low MCV Symptoms: Unique symptoms for low MCV (microcytosis) can include brittle nails, hair loss, and cold extremities, most commonly resulting from iron deficiency.
Medical Consultation is Key: Since many symptoms overlap and can be caused by various issues, a blood test and a doctor's evaluation are essential for accurate diagnosis.
Diagnosis Drives Treatment: Treatment depends entirely on the root cause; addressing nutrient deficiencies with diet or supplements or managing underlying conditions like liver disease can help normalize MCV levels.

What is Mean Corpuscular Volume (MCV)?

Mean Corpuscular Volume (MCV) measures the average size of your red blood cells (RBCs) and is part of a standard complete blood count (CBC). Normal MCV for adults is typically 80-100 fL. Abnormal MCV, either too high (macrocytosis) or too low (microcytosis), can affect oxygen transport and indicate conditions like anemia, but it is not a diagnosis on its own.

Symptoms of high MCV (Macrocytosis)

High MCV, or macrocytosis, means red blood cells are larger than normal. Symptoms, if present, relate to the underlying cause and anemia, often progressing over time.

Common symptoms of high MCV

Symptoms can include fatigue, weakness, pale or jaundiced skin, and shortness of breath. Cognitive issues and neurological symptoms like tingling or numbness are possible, especially with vitamin B12 deficiency. A smooth tongue or digestive problems like diarrhea can also occur.

Symptoms of low MCV (Microcytosis)

Low MCV, or microcytosis, means red blood cells are smaller than normal, frequently caused by iron deficiency anemia. Symptoms are often due to reduced oxygen delivery.

Common symptoms of low MCV

Key symptoms include excessive fatigue, weakness, and pale skin. Shortness of breath, dizziness, cold hands and feet, brittle nails, hair loss, and headaches may also occur. A rapid heartbeat (tachycardia) can be the body's attempt to compensate for low oxygen levels.

Comparison of high and low MCV symptoms

Many symptoms of high and low MCV overlap due to the shared issue of inefficient oxygen transport. However, some symptoms are more common or specific to one condition. Below is a comparison:


Symptom	High MCV (Macrocytosis)	Low MCV (Microcytosis)
Fatigue/Weakness	Very common, often pronounced.	Very common and persistent.
Pale Skin	Can occur, sometimes with a yellow tint (jaundice).	Very common and often visible.
Shortness of Breath	Common, especially with exertion.	Common, even with mild activity.
Tingling/Numbness	Specific to vitamin B12 deficiency.	Not typically associated with low MCV.
Cognitive Issues	Common with B12/folate deficiency.	Can occur, but less distinct.
Digestive Problems	Diarrhea, loss of appetite.	Can include constipation with iron deficiency.
Nail/Hair Changes	Possible hair loss.	Brittle nails, hair loss with severe deficiency.
Heart Palpitations	Can occur due to anemia.	Can occur due to anemia.

What to do if you suspect abnormal MCV

If you have persistent symptoms like fatigue or paleness, consult a doctor for a CBC. Further tests may be needed to find the cause.

Diagnosis and treatment

Diagnosis involves blood tests, including MCV and levels of B12, folate, and iron. Medications can also affect MCV. Treatment targets the cause: diet or supplements for deficiencies, or managing underlying conditions like liver disease.

For additional health information, resources like the National Institutes of Health offer details on various conditions(https://pubmed.ncbi.nlm.nih.gov/). Always consult a medical professional for personal health advice.

Conclusion

Abnormal MCV levels are important indicators from blood tests, suggesting potential health issues related to red blood cell size. Symptoms often reflect poor oxygen transport and vary based on the cause, such as vitamin deficiencies or iron deficiency. Persistent symptoms warrant medical evaluation for diagnosis and treatment. Prompt action is crucial for managing the underlying cause and improving health.

Frequently Asked Questions

A normal MCV range for adults is typically between 80 and 100 femtoliters (fL), although this can vary slightly by laboratory. Values outside this range may indicate microcytosis (low) or macrocytosis (high).

While stress and poor sleep can contribute to generalized fatigue, they do not directly cause abnormal MCV levels. The underlying cause of abnormal MCV is typically related to nutritional deficiencies, chronic disease, or other medical issues.

For high MCV due to B12 or folate deficiency, increasing your intake of vitamin B12-rich foods (eggs, meat, fish, dairy) and folate-rich foods (leafy greens, legumes, fortified grains) is beneficial.

To address low MCV from iron deficiency, focus on iron-rich foods such as lean meats, legumes, dark leafy greens, and fortified cereals. Consuming vitamin C along with iron can also enhance absorption.

Yes, some individuals may have mildly elevated or reduced MCV levels without experiencing any noticeable symptoms. In these cases, the abnormality may be temporary or require monitoring.

Chronic and excessive alcohol consumption is a common cause of high MCV. Alcohol can interfere with nutrient absorption, particularly B vitamins, leading to macrocytosis.

Yes, some medications can affect MCV levels. Chemotherapy drugs, certain anti-seizure medications, and drugs that impact vitamin B12 or folate absorption are known culprits.

While high MCV can be associated with some bone marrow disorders like myelodysplastic syndromes, a high MCV result alone is not a direct indicator of cancer. Nutrient deficiencies, liver disease, or alcohol use are far more common causes.