In short
- MCV is the average size of your red blood cells. A low MCV (small cells) most often points to iron deficiency. A high MCV (large cells) points to B12 or folate deficiency, alcohol, or liver or thyroid disease.
- MCH is the average amount of hemoglobin in one red cell and usually moves with MCV. MCHC is how densely that hemoglobin fills the cell.
- Low MCH and low MCHC together mean small, pale cells. Iron deficiency is the most common reason; thalassemia trait is the main one to rule out.
- The indices point to a cause but do not diagnose one. Read them with hemoglobin, ferritin, B12 and RDW.
- A high MCHC is rare and is often a sample problem, so the test is usually repeated.
MCV, MCH and MCHC sit in the middle of every complete blood count, and most people skip them. They matter most when hemoglobin is low or borderline, because they show where to look for the cause. Here you get the ranges we use, the source behind them, and the patterns that separate iron, B12 and inherited causes.
What does MCV mean in a blood test?
MCV (mean corpuscular volume) is the average volume of one red blood cell, measured in femtoliters (fL). Small cells give a low MCV and large cells give a high MCV. Its main job is to sort anemia by cause, because small cells point to a different problem than large cells.
The other two indices build on it. MCH (mean corpuscular hemoglobin) is the average weight of hemoglobin in one cell, in picograms (pg). MCHC (mean corpuscular hemoglobin concentration) is how densely hemoglobin fills the cell. MCH depends on cell size, while MCHC corrects for it.
A common trap when reading reports: European labs print MCHC in g/L (for example 330), while US labs use g/dL (33.0). It is the same value. Divide g/L by 10 to compare them.
What are normal MCV, MCH and MCHC values?
In our knowledge base, MCV is within range from 82 to 98 fL and MCH from 27.1 to 33.3 pg. MCHC is within range from 317 to 357 g/L (31.7 to 35.7 g/dL).
| Marker | Low | Within range | High |
|---|---|---|---|
| MCV (fL) | under 82 | 82–98 | over 98 |
| MCH (pg) | under 27.1 | 27.1–33.3 | over 33.3 |
| MCHC g/L (US g/dL) | under 317 (31.7) | 317–357 (31.7–35.7) | over 357 (35.7) |
Source: NORIP (Nordic Reference Interval Project), Nordin et al., 2004, as stored in the Blood Lab 360 knowledge base. Reference ranges differ between laboratories and analyzers, so the range printed on your report applies.
Textbooks often use rounder cut-offs. StatPearls describes microcytosis as an MCV below 80 fL and macrocytosis as an MCV above 100 fL. So an MCV of 99 fL can be flagged on one report and not on another.
What does low MCV mean?
A low MCV means your red blood cells are smaller than usual, which doctors call microcytosis. The most common cause is iron deficiency. Other causes are thalassemia trait, an inherited change in how hemoglobin is made, and anemia of chronic disease. Lead poisoning is a rare cause.
Iron deficiency comes from blood loss, low intake or poor absorption. In women with heavy periods the reason is often clear. In men and in women after menopause, StatPearls advises looking for blood loss from the gut, such as an ulcer, because it can be silent.
In thalassemia trait, iron stores are normal and iron does not fix the small cells. Extra iron you do not need can do harm, so the cause should be clear first.
Why are MCH and MCHC low?
Low MCH and low MCHC mean each red cell carries less hemoglobin than usual, so the cells look pale (hypochromic). This almost always comes with a low MCV. Iron deficiency is the most common reason, and thalassemia trait is the main alternative.
MCH usually falls together with MCV, because a smaller cell holds less hemoglobin. MCHC corrects for size. That is why MCH can be low while MCHC stays normal, when cells are small but not pale. A clearly low MCHC most often goes with iron deficiency.
What does high MCV mean?
A high MCV means your red blood cells are larger than usual, which doctors call macrocytosis. Common causes are vitamin B12 or folate deficiency, regular heavy drinking, liver disease and an underactive thyroid. Some medicines raise MCV, and so do conditions with many young red cells (reticulocytes).
The size of the shift gives a hint. StatPearls notes that mild macrocytosis, an MCV of 100 to 110 fL, is more often due to benign conditions. An MCV above 110 fL is more often due to B12 or folate deficiency or a bone marrow disease.
Medicines named in that source include methotrexate, hydroxyurea and zidovudine; do not stop one on your own.
B12 deficiency can also cause tingling in the hands or feet, poor balance and memory problems. These signs matter more than the exact MCV. Read more in vitamin B12 and folate.
Is a high MCHC a problem?
A high MCHC is uncommon and is often a measurement issue rather than a disease. Broken red cells in the tube (hemolysis) or very fatty plasma (lipemia) can push it up. A real, repeated high MCHC can point to hereditary spherocytosis, an inherited condition with round, fragile red cells.
The usual first step is a new sample. If MCHC stays high, your doctor decides which further tests make sense.
Which patterns point to which cause?
The indices are most useful as a set. The table shows common combinations and the tests that usually settle the question, as a starting point for your doctor.
| Pattern on the report | Most likely direction | Next step |
|---|---|---|
| Low MCV, low MCH, low MCHC, high RDW, low ferritin | Iron deficiency | Ferritin; look for blood loss in men and after menopause |
| Low MCV (often very low), red cell count normal or high for the degree of anemia, normal RDW, normal ferritin | Thalassemia trait | Hemoglobin electrophoresis or HPLC, ordered by a doctor |
| High MCV, low or borderline B12 or folate | B12 or folate deficiency | B12 and folate; extra tests when B12 is in the grey zone |
| Mildly high MCV (100–110 fL), normal B12 and folate | Alcohol, liver, thyroid or medicines | Liver tests, TSH, a review of medicines |
| Normal MCV, high RDW | Early deficiency or iron and B12 deficiency together | Ferritin, B12, folate |
| Only MCHC high, everything else normal | Sample problem; rarely spherocytosis | Repeat sample |
Source for the patterns: StatPearls, Microcytic Hypochromic Anemia (2023) and Macrocytic Anemia (2025). Ferritin and B12 limits come from the Blood Lab 360 knowledge base.
Two practical points. First, in our knowledge base ferritin below 15 µg/L means empty iron stores, and 15 to 30 µg/L is borderline (WHO 2020). For vitamin B12, under 133 pmol/L is low and 133 to 258 pmol/L is a grey zone (NICE 2024). Second, iron and B12 deficiency can occur together. Small and large cells then average out, so MCV can look normal while RDW rises. Our article on high RDW explains that pattern.
Do MCV and MCH matter if my hemoglobin is normal?
Yes, but they are less urgent. Abnormal indices with normal hemoglobin often mean an early deficiency or an inherited trait rather than anemia. The WHO 2024 guideline defines anemia by hemoglobin: below 120 g/L (12.0 g/dL) in non-pregnant women and below 130 g/L (13.0 g/dL) in men aged 15 to 65.
WHO also grades anemia. Mild is 110–119 g/L in women and 110–129 g/L in men. Moderate is 80–109 g/L and severe is below 80 g/L for both. Our app uses these sex-specific cut-offs. Without your sex, a hemoglobin of 120 to 130 g/L cannot be rated, because it is normal for a woman and low for a man.
A low MCV with normal hemoglobin is still worth a ferritin test, because iron stores empty before hemoglobin falls. See ferritin and iron for how that happens.
See a doctor soon if abnormal indices come with hemoglobin below 110 g/L (11.0 g/dL) or a hemoglobin that keeps dropping between tests. The same applies to breathlessness at rest, chest pain, fainting, black or bloody stools, or very heavy periods. With a high MCV, tingling, numbness or balance problems also need prompt care. Hemoglobin below 80 g/L is severe anemia by the WHO definition and needs medical care without delay.
How Blood Lab 360 reads this
Blood Lab 360 never reads MCV, MCH or MCHC on their own. It first checks hemoglobin against the WHO cut-off for your sex. Then it reads the indices as a group, together with RDW, ferritin, B12 and folate when they are on your report. Each range comes from the knowledge base shown above, with its source named.
If your sex or age is missing, the app asks for it before rating hemoglobin. When MCV or MCH is outside the range, the suggested re-test is after about 16 weeks; for MCHC it is about 12 weeks. The indices change slowly, as new red cells replace old ones. The app explains your values; it does not diagnose, and a flagged pattern is a reason to talk to your doctor.
Frequently asked questions
What does it mean if MCH and MCHC are both low?
Your red cells carry less hemoglobin than usual and look pale. The most common cause is iron deficiency, so ferritin is the next test. If ferritin is normal and MCV is very low, thalassemia trait is the main alternative.
Is a low MCV serious?
A slightly low MCV with normal hemoglobin is rarely urgent. It is still a clue worth following, most often to low iron stores. A low MCV with low hemoglobin, symptoms or signs of blood loss needs a doctor soon.
What does a high MCV mean?
Your red cells are larger than usual. Common causes are B12 or folate deficiency, alcohol, liver disease, an underactive thyroid and some medicines. An MCV above 110 fL makes B12 or folate deficiency or a marrow cause more likely.
Can I have a low MCV without anemia?
Yes. MCV can drop before hemoglobin falls below the WHO cut-off, for example in early iron deficiency. Thalassemia trait also often gives small cells with normal or near-normal hemoglobin.
Should I take iron if my MCV is low?
Only after ferritin confirms low iron stores. In thalassemia trait iron stores are normal, and extra iron does not help and can do harm. Agree the dose and duration with your doctor.
Why is my MCV flagged on one report but not on another?
Labs use different reference ranges. Our knowledge base uses 82 to 98 fL, while textbooks often use 80 to 100 fL. A value right at the limit carries little weight on its own.
