What is the MCV Test?
The MCV test, or Mean Corpuscular Volume test, is a blood test that measures the average size of your red blood cells (RBCs). It is one of the standard values included in a Complete Blood Count (CBC) test. Instead of counting how many RBCs you have, the MCV tells you whether your red cells are small, normal, or large in size.
This measurement helps doctors find the type of anemia you may have. For example, if RBCs are too small, it may suggest iron deficiency. If they are too large, it may point towards vitamin B12 or folate deficiency.
Where is MCV Determined in the Body?
MCV is not directly produced in the body. Instead, it is a calculated value that comes from analyzing your blood sample in a lab. The size of your red blood cells depends on many factors: how your bone marrow is working, and whether your body has enough nutrients like iron, vitamin B12, and folic acid. Some diseases also affect RBC size, making them unusually small or large.
Main Functions and Importance of MCV
Classifies Types of Anemia:
- Low MCV (microcytic): Small RBCs, usually from iron deficiency.
- Normal MCV (normocytic): Normal-sized RBCs, but anemia may still occur due to blood loss or chronic illness.
- High MCV (macrocytic): Large RBCs, often from B12 or folic acid deficiency.
Guides Diagnosis: Helps doctors find the cause of anemia quickly.
Used with Other CBC Values: Doctors check MCV along with Hemoglobin (Hb), RBC count, and MCH to get a full picture.
Causes of Low MCV (Microcytic Anemia)
When MCV is less than 80 fL, it is called microcytic anemia. Common causes include:
- Iron Deficiency: The most common reason worldwide.
- Thalassemia: A genetic condition affecting hemoglobin production.
- Chronic Blood Loss: Such as ulcers, piles, or heavy periods.
- Lead Poisoning: Lead affects hemoglobin formation.
- Sideroblastic Anemia: A condition where the body cannot use iron properly to make hemoglobin.
Symptoms of Low MCV
Since low MCV usually means anemia, symptoms overlap with anemia signs:
- Tiredness and weakness
- Pale skin or lips
- Shortness of breath
- Dizziness or light-headedness
- Cold hands and feet
- Reduced focus and headaches
Causes of High MCV (Macrocytic Anemia)
When MCV is more than 100 fL, it is called macrocytic anemia. Causes include:
- Vitamin B12 Deficiency: Often due to poor diet or absorption problems.
- Folic Acid Deficiency: From low intake, pregnancy, or certain conditions.
- Alcohol Abuse: Long-term drinking damages blood cell production.
- Liver Disease: Affects RBC development.
- Hypothyroidism: Low thyroid hormone can lead to larger RBCs.
- Medications: Some chemotherapy and HIV medicines cause high MCV.
- Bone Marrow Disorders: Such as myelodysplasia.
Symptoms of High MCV
High MCV often shares symptoms with anemia, but some are specific:
- Fatigue and weakness
- Difficulty concentrating
- Pale or slightly yellow skin
- Numbness or tingling (common in B12 deficiency)
- Memory changes or mood issues
- Swollen, red tongue (in B12 or folate deficiency)
Reference Ranges
(may differ by lab)
Normal MCV: 80 to 100 femtoliters (fL)
Low MCV (< 80 fL): Microcytic (small RBCs)
Normal MCV (80–100 fL): Normocytic (normal RBC size)
High MCV (> 100 fL): Macrocytic (large RBCs)
Sample Type
Sample Taken: Whole blood
Tube Used: Lavender-top (EDTA tube)
Blood is usually taken from a vein in the arm. Results are available quickly as part of a CBC report.
Test Preparation
Usually no fasting is needed for an MCV test.
Drink water before the test to avoid dehydration.
Inform your doctor if you take medicines such as chemotherapy drugs, anti-HIV drugs, or long-term alcohol intake, as these can affect results.
Sometimes doctors order the MCV test along with vitamin B12 and folate tests for confirmation.
When to Consult a Doctor
If you feel weak, tired, or pale without reason.
If you have numbness, tingling, or memory problems.
If your MCV result is consistently high or low outside the normal range.
If you have a family history of anemia or genetic blood disorders.
Pregnant women and people with chronic illness should consult doctors regularly for CBC and MCV monitoring.
~END~