MCV Blood Test High Symptoms: Causes, Risks, and What to Do Next

Imagine you’ve gone for a routine blood test, maybe as part of your yearly checkup. A few days later, your doctor calls and mentions that your MCV level is high. You may be wondering: what does that mean? Should you be worried?

MCV stands for Mean Corpuscular Volume, and it’s a measurement that tells doctors the average size of your red blood cells. It might sound technical, but in reality, MCV is an important clue about your overall health. When your MCV is high, it usually means your red blood cells are larger than normal, which doctors call macrocytosis.

A high MCV result by itself doesn’t give a full diagnosis, but it does act as a red flag that something in your body needs attention—whether it’s a vitamin deficiency, a thyroid problem, alcohol use, or something more complex.

In this guide, we’ll walk through everything you need to know about high MCV results, including what the test measures, what high levels really mean, what symptoms you may notice, the most common causes, and the steps you can take to bring your results back into balance. By the end, you’ll understand not just what the numbers mean, but also how to respond in a way that protects your health long-term.

What Is an MCV Blood Test?

Before diving into what it means when your MCV is high, let’s first understand the basics of the test. MCV is short for Mean Corpuscular Volume, and it’s one of the standard measurements included in a Complete Blood Count (CBC). The CBC is one of the most commonly ordered blood tests and gives doctors insight into your overall health by measuring several different aspects of your blood.

Specifically, MCV looks at the average size of your red blood cells. Red blood cells, also called erythrocytes, are responsible for carrying oxygen from your lungs to the rest of your body and then bringing carbon dioxide back to your lungs to be exhaled. Their size matters because it can provide valuable clues about your health.

The normal MCV range for most adults is typically 80–100 femtoliters (fL). If your MCV falls within this range, it means your red blood cells are about the right size. If the number is lower than 80, your red blood cells are smaller than normal (microcytic), which is often linked to conditions like iron-deficiency anemia. If your MCV is higher than 100, your red blood cells are larger than normal (macrocytic), which is where the concern about high MCV comes in.

So, in simple terms: MCV tells doctors whether your red blood cells are too small, too large, or just right. And each of those scenarios points to different possible health conditions.

What Does It Mean If Your MCV Is High?

When your test results show a high MCV, it means your red blood cells are larger than normal. Doctors call this condition macrocytosis.

Now, having bigger red blood cells might not sound like a big deal. But here’s the catch: larger red blood cells often don’t function as efficiently as normal-sized ones. They may have trouble carrying oxygen, which can lead to symptoms like fatigue, weakness, and difficulty concentrating.

It’s important to understand that a high MCV result doesn’t diagnose a disease by itself. Instead, it tells your doctor that something underlying is likely affecting your blood cells. High MCV can be linked to nutritional deficiencies (like not getting enough vitamin B12 or folate), long-term alcohol use, liver or thyroid problems, or, in rare cases, bone marrow disorders.

Think of MCV as an indicator light on your car dashboard. If the light comes on, it doesn’t tell you exactly what’s wrong with the engine, but it does tell you to look under the hood. Similarly, high MCV tells your doctor it’s time to investigate further.

Common Symptoms of High MCV Levels

Here’s where things get a little tricky: high MCV itself doesn’t cause symptoms. Instead, the symptoms come from whatever is causing the red blood cells to be larger than normal. That’s why two people with high MCV might feel very different depending on the underlying reason.

Still, there are some common patterns. People with high MCV due to vitamin B12 or folate deficiency, for example, often notice:

• Fatigue and weakness: Since larger red blood cells may not carry oxygen as efficiently, your body’s tissues may not get enough fuel, leaving you tired and drained.
• Shortness of breath: Even light physical activity can leave you winded because your blood isn’t delivering oxygen effectively.
• Dizziness or lightheadedness: Low oxygen levels in the brain can make you feel unsteady or faint.
• Pale or yellowish skin: Some conditions linked to high MCV can cause anemia, which shows up as pallor, or jaundice, which gives skin and eyes a yellow tint.
• Numbness or tingling in hands and feet: Especially in B12 deficiency, nerve damage can cause pins-and-needles sensations.
• Memory problems or trouble concentrating: Oxygen delivery to the brain is crucial for focus and cognition.

Not everyone experiences these symptoms, though. In fact, many people with high MCV have no noticeable symptoms at all and only learn about it from routine bloodwork. That’s why regular checkups are so important—blood tests can catch issues early, before they cause obvious problems.

Causes of High MCV (Macrocytosis)

There’s no single reason why MCV might be high. Instead, it’s usually linked to one of several possible causes. Understanding these helps doctors figure out the best way to treat it.

One of the most common causes is vitamin deficiencies. Both vitamin B12 and folate (vitamin B9) are crucial for making healthy red blood cells. Without enough of these nutrients, your body produces larger but less effective red blood cells, leading to macrocytosis. This is often seen in people with poor diets, digestive conditions like celiac or Crohn’s disease, or in older adults who have trouble absorbing vitamins from food.

Another major factor is alcohol use. Even without other health problems, drinking large amounts of alcohol regularly can increase MCV. That’s because alcohol interferes with red blood cell production in the bone marrow and can also lead to vitamin deficiencies.

Liver disease is another frequent culprit. The liver plays a central role in processing nutrients and toxins. When it isn’t working properly—due to conditions like hepatitis, fatty liver, or cirrhosis—red blood cell size can be affected.

Hypothyroidism, or an underactive thyroid, can also cause high MCV. The thyroid gland produces hormones that regulate many body functions, including red blood cell production. When thyroid hormone levels are too low, red blood cells can become abnormally large.

Certain medications can also raise MCV. Some chemotherapy drugs, antiretrovirals used to treat HIV, and seizure medications interfere with DNA synthesis, which leads to macrocytosis.

In rare cases, high MCV can be linked to serious bone marrow disorders such as myelodysplastic syndrome (MDS). These conditions affect the bone marrow’s ability to make normal blood cells and are more common in older adults.

RELATED READ: High White Blood Cell Count: What It Really Means & How To Lower It Naturally

How Doctors Diagnose and Evaluate High MCV

If your blood test shows a high MCV, your doctor won’t stop there. Instead, they’ll likely order additional tests and ask detailed questions about your health and lifestyle to find the cause.

First, they’ll probably repeat or review your Complete Blood Count (CBC) in detail. They’ll also look at other markers like hemoglobin, hematocrit, and red blood cell distribution width (RDW). Together, these numbers give a fuller picture of your blood health.

Next, they may order blood tests for vitamin B12 and folate to check for deficiencies. If these levels are low, it often explains the elevated MCV.

If vitamin levels are normal, they may test your liver function or thyroid function to see if those organs are contributing to the issue. They’ll also review your medications and alcohol use, since these are frequent contributors.

In some cases, if other tests don’t explain the abnormal MCV, your doctor may order a bone marrow biopsy. This test is much less common and is usually only done if a bone marrow disorder is strongly suspected.

How to Respond if You Have High MCV

Getting a lab report that shows high MCV can be unsettling, but the first and most important step is this: don’t panic. Many causes of high MCV are reversible, and with proper treatment, your blood levels can return to normal.

The best thing you can do is work closely with your doctor to identify the underlying reason. Depending on the cause, treatment may include:

• Improving your diet: Eating foods rich in vitamin B12 (like meat, fish, eggs, and dairy) and folate (leafy greens, beans, citrus fruits) can correct deficiencies.
• Taking supplements: If diet alone isn’t enough, your doctor may recommend vitamin supplements or, in the case of severe B12 deficiency, injections.
• Cutting back on alcohol: Reducing or stopping alcohol consumption can quickly improve MCV in many people.
• Treating thyroid or liver conditions: Managing these health issues with medication or lifestyle changes can normalize red blood cell size.
• Adjusting medications: If a prescription drug is the cause, your doctor may adjust your dosage or switch you to another medication.

Remember, the key is not just lowering your MCV number but treating the health issue behind it.

Can High MCV Be Prevented?

Not every case of high MCV can be prevented, but you can lower your risk by focusing on overall health habits. Eating a well-balanced diet rich in B vitamins is one of the most effective strategies. This includes foods like spinach, lentils, fortified cereals, chicken, fish, and eggs.

Moderating alcohol use also makes a big difference. Even if you don’t drink heavily, cutting back can help your liver and bone marrow function better.

Finally, staying on top of regular checkups allows your doctor to catch changes in your blood work early. Managing chronic conditions like thyroid disease or liver disease promptly can prevent MCV from rising in the first place.

When to See a Doctor

If your blood test shows a high MCV, it’s always a good idea to follow up with your doctor, even if you feel fine. Many underlying causes don’t cause obvious symptoms at first, but they can become more serious over time.

You should also see a doctor promptly if you experience unexplained fatigue, shortness of breath, numbness in your hands and feet, or persistent weakness. These may be signs of anemia or vitamin deficiency that need medical attention.

Key Takeaways

High MCV means your red blood cells are larger than normal, a condition known as macrocytosis. It doesn’t point to a single disease but instead acts as a clue that your body may be dealing with a vitamin deficiency, alcohol-related changes, thyroid or liver issues, or, less commonly, bone marrow disorders.

The symptoms of high MCV usually come from the underlying cause rather than the high number itself, with fatigue, weakness, and nerve problems among the most common.

Fortunately, many causes of high MCV are treatable and even reversible. By working with your doctor, improving your diet, limiting alcohol, and staying on top of routine health checks, you can take control of your blood health and protect your long-term well-being.

FAQs

1. What level of MCV is considered dangerously high?

Most doctors consider an MCV above 100 fL to be high, but “dangerously high” depends on the underlying cause. For example, an MCV of 110 due to a B12 deficiency can be corrected with treatment, while the same number from a bone marrow disorder might require more intensive care.

2. Can dehydration cause high MCV?

Dehydration typically affects other blood markers like hemoglobin and hematocrit rather than MCV. However, severe dehydration can sometimes skew test results.

3. Is high MCV always linked to anemia?

Not always. While high MCV often points to macrocytic anemia, some people with high MCV don’t have anemia at all. That’s why additional tests are needed.

4. Can stress raise MCV levels?

Stress alone doesn’t usually raise MCV, but long-term health effects of stress—such as poor nutrition or alcohol use—can indirectly contribute.

5. Does high MCV mean cancer?

In most cases, no. High MCV is more commonly linked to vitamin deficiencies, alcohol use, or thyroid problems. Rarely, it can be linked to bone marrow cancers, but this is not the most common cause.