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Overview

What Is an MCV Blood Test?

MCV stands for mean corpuscular volume. An MCV blood test measures the average size of your red blood cells and is usually reported as one part of a complete blood count (CBC), rather than as a standalone diagnosis.

Red blood cell size can provide clues about how your blood is carrying oxygen and whether further evaluation may be needed. Your clinician interprets what MCV means alongside hemoglobin, hematocrit, red blood cell count, other CBC results, symptoms, medical history, and sometimes additional blood tests.

When It Is Needed

When Is an MCV Blood Test Needed?

MCV is most often calculated automatically as part of a complete blood count during routine blood work or an evaluation of anemia and other blood-count abnormalities. A clinician may review the MCV in a blood report when symptoms, other results, or a known condition raise a question about red blood cell health.

  • Fatigue or weakness may lead a clinician to review the MCV along with the rest of the CBC.
  • Pale skin or shortness of breath can prompt blood work for possible anemia or another condition.
  • An abnormal hemoglobin, hematocrit, or red blood cell count may make the MCV more important to interpret.
  • Suspected iron, vitamin B12, or folate deficiency may be evaluated with an MCV and other tests.
  • The MCV may be monitored when a person has a known blood, nutritional, liver, or other medical condition.

Preparation

How to Prepare for an MCV Blood Test

An MCV measurement alone usually does not require special preparation or fasting. However, if your blood work includes other tests, the laboratory or clinician may give you fasting instructions, so follow the directions provided before your appointment.

Tell the healthcare professional about your medicines, supplements, recent illness, and any relevant dietary restrictions. Do not stop a prescribed medicine or treatment unless your clinician specifically tells you to do so.

During the Test

What Happens During an MCV Blood Test?

An MCV blood test is usually a single blood-draw session. A healthcare professional cleans the skin, inserts a small needle into a vein, collects blood into a tube, removes the needle, and applies pressure and a bandage. The sample is then sent to a laboratory, where the MCV is measured as part of the blood count.

Risks

Are There Risks From an MCV Blood Test?

  • Brief pain or stinging may occur when the needle enters the vein.
  • A small bruise may develop near the puncture site.
  • Minor bleeding can occur after the needle is removed.
  • Infection at the puncture site is uncommon but possible.
  • Some people feel lightheaded or faint during or after a blood draw.

When to get help

Report unusual symptoms after the blood draw

Tell the collector if you feel faint. Persistent bleeding, worsening swelling or pain, or redness and drainage at the puncture site should be discussed with a healthcare professional.

Results

What Do MCV Blood Test Results Mean?

The laboratory reports MCV as a number, commonly in femtoliters (fL), along with a reference range. The range can vary by laboratory, age, and other factors, so there is no single universal cutoff that applies to everyone. An MCV blood test result should be interpreted with the rest of the CBC and your clinical information.

MCV patternWhat it describesPossible considerations
Within the laboratory reference rangeAverage red blood cell size falls within that laboratory's stated rangeInterpret with hemoglobin, hematocrit, red blood cell count, symptoms, and medical history
Low MCVRed blood cells are smaller than the laboratory reference rangeIron deficiency, some inherited hemoglobin conditions, or other causes of microcytosis
High MCVRed blood cells are larger than the laboratory reference rangeVitamin B12 or folate deficiency, alcohol use, liver disease, certain medicines, or other causes of macrocytosis

An abnormal MCV blood test may lead your clinician to review the complete blood count more closely and consider iron studies, vitamin levels, medication and alcohol history, liver or thyroid testing, or other investigations as appropriate. A high MCV, raised MCV in a blood test, or low MCV does not establish a diagnosis by itself. Discuss an abnormal result with your clinician rather than trying to interpret it without context.

Diseases & Conditions

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