Femtolitre is a unit of measurement for very small volumes of liquid. It equals one quadrillionth of a litre, which is 0.000000000000001 litres. In medical laboratory reports, this unit often appears when describing the size of cells or their components.
What is the unit used for?
In everyday medical practice, the term comes up most often in connection with blood tests. It plays a particular role in what is known as a full blood count. For example, the volume of a single red blood cell (erythrocyte) is given in femtolitres. This value is called the MCV, which stands for mean corpuscular volume. A typical normal value for MCV is between 80 and 100 femtolitres. This means that a single red blood cell has, on average, that amount of volume.
Why are such small units necessary?
The cells in the human body are tiny. A litre is a size we encounter in everyday life, roughly equal to a large carton of juice. A femtolitre, by comparison, is so small that it describes the volume of individual cells or even parts of cells. Without such fine units of measurement, laboratory equipment could not precisely state how large or small a cell really is. This matters especially in blood tests, because the size of cells can give clues about various conditions.
Typical values in a laboratory report
A value in femtolitres usually appears in connection with the MCV, but this unit can also come up for the volume of other blood cells. If a laboratory report states, for example, that the MCV is 85 femtolitres, this means that the red blood cells have that volume on average. If the value is significantly above or below this, it may point to certain changes in the blood count.
What does this mean for your health?
The measurement in femtolitres is, in itself, purely technical and simply describes a unit of measurement. It is not a medical condition and not a diagnosis. Only when considered alongside other laboratory values and the specific clinical question will a doctor assess whether a value is noteworthy. A single value in femtolitres, such as the MCV, is therefore just one small piece of the overall laboratory picture.
How is the volume measured?
Modern laboratory equipment counts and measures blood cells using light or electrical impulses. The volume of each individual cell is determined, and an average value is then calculated. This is how the MCV value is produced, for example. The measurement is carried out automatically and very precisely, so that even the smallest deviations can be detected.
Is there more than one meaning?
Femtolitre is an internationally used unit of measurement for volume. In medicine and biology, the term almost always refers to the volume of cells or very small amounts of fluid. In other technical or scientific fields, the unit can also be used, for example in chemistry or physics, when very small amounts of liquid need to be described. The context in which the value appears is always what matters most. In medical reports, femtolitre almost always refers to the volume of a cell, usually red blood cells.
What to do if you have questions about laboratory values?
If you are unsure about values given in femtolitres in a laboratory report, speaking with your treating doctor is the best step. They can explain whether the value falls within the normal range and what it means in relation to other laboratory values. The unit femtolitre itself is simply a unit of measurement and, without further context, says nothing about a condition or any need for action.
Femtolitre is therefore a very small unit of volume, used mainly in laboratory medicine to describe the size of cells precisely. The measurement helps to interpret blood values more clearly, but on its own it is not an indication of any illness.
