MCV in men: a value of 89, too low or too high

MCV, in full mean corpuscular volume, is the average volume of a single red blood cell, expressed in femtolitres (fl). The value comes out of the complete blood count and says something different from haemoglobin: haemoglobin tells you how much oxygen-carrying protein you have, while MCV tells you how big the cells carrying that protein are. The two belong together. A low haemoglobin without an MCV is a result without a direction; with the MCV beside it, anaemia splits into three tracks: microcytic below 80 fl (small cells), normocytic between 80 and 100 fl, and macrocytic above 100 fl (large cells).

The reference range shown on this page runs from 80 to 100 fl and is deliberately not split by sex, so the same limits apply to men as to everyone else. What differs is what a deviation means. The table below reads a specific value against what it says for an adult man, and against the question a doctor usually asks next.

One caveat applies to every MCV: it is an average, not a description of spread. If you have a population of small cells and a population of large cells at the same time, they cancel each other out in the average and a perfectly tidy number comes out. That is why MCV is always read together with the RDW, the measure of variation in cell size. A normal MCV with a raised RDW is a different story from a normal MCV with a normal RDW.

In a man, an MCV that is too low is rarely a result to shrug off. The adult male body has no normal route along which blood disappears with any regularity. So if the iron stores are empty, that iron went somewhere. That makes the combination of an MCV below 80 fl and a low ferritin in a man not a detail you close off with a supplement, but a result that deserves an explanation.

The question a doctor routinely asks in that situation is about the gastrointestinal tract: in men that is where slow, unnoticed blood loss most often occurs. That is emphatically not a diagnosis and usually not a reason to panic. Low intake, reduced absorption, or blood loss from an already known cause often explain it. But it is the conversation to have with your doctor before you start taking iron on your own. Taking iron without knowing the cause does two things at once: it makes your iron values look better, and it makes the question of where the iron went invisible.

At the other end of the scale sits alcohol. Regular alcohol use raises MCV directly and in a dose-related way, so without any vitamin B12 deficiency being involved. That is not a moral point but a measurement point, and it comes with one awkward property: it is slow. After you cut down or stop, the MCV only falls on the timescale over which red cells are replaced, up to about three months.

For a man who tracks his blood values year on year, that is a quiet distortion. You are then comparing not only last year's health with this year's, but also your drinking in the quarter before each blood draw. Anyone who takes his own numbers seriously notes that alongside them.

And then the point that applies to every result: a normal MCV does not rule out a deficiency. In a combined deficiency, iron plus vitamin B12 or folate, small cells and large cells exist side by side and average out to a perfectly tidy value between 80 and 100 fl. The RDW, the measure of variation in cell size, is usually raised in that scenario. A normal MCV is reassuring, then, but it is not proof.

MCV is almost never ordered on its own; it sits in the standard complete blood count. Have that panel drawn when you have been unusually tired for more than a couple of weeks, notice clearly less energy than you are used to, or when an earlier result showed a low haemoglobin without it becoming clear why. If your MCV is too low, ferritin belongs on the same request; if it is too high, vitamin B12 and thyroid values belong with it.

Timing decides how usable the result is, and two things matter here. First, red cells swell in an EDTA tube when the sample sits for a long time. A tube analysed only after 24 hours gives an artificially raised MCV, and a lowered MCHC. So an isolated, mildly raised MCV with an otherwise normal blood count is first a question about the sample and only then a clinical question. Second, if you have just started iron or vitamin B12, your bone marrow produces a lot of young, large cells in the first weeks, and that lifts the MCV temporarily. Wait until that wave has passed before rechecking, otherwise you are measuring the response to treatment rather than your baseline.