Measuring Flow

Measuring your menstrual flow is easy when you have a menstrual cup. If you are not able to measure your menstrual flow with a menstrual cup then you will have to estimate the amount of blood that is lost.

The standard amounts given as "normal" (between 10mls and 100mls), and "average" (30-40mls) flow may seem conservative to many women. When women have been polled on this topic in informal polls, more than the expected number of women reported losses of over 100mls.

One debate on this is that they measure "blood" loss to obtain those figures, and that only part of what constitutes a menstrual flow is actually blood.

How they measure menstrual flow

There are 3 methods that health care professionals can use for measuring a menstrual flow (other than the obvious collection in a menstrual cup)

1). Weighing used and fresh pads, taking the weight difference to be the blood lost.

Weighing pads would be rather time consuming, but would give a more accurate measurement than comparing your flow to images. However sweat and vaginal secretions may also be on the pad, which may affect its weight. Also some evaporation may occur too, and dry blood would presumably weigh less than wet blood.

2). Using images of disposable pads rated from "spotting"/"light" to "soaked"/"Heavy" to calculate flow, with the pictures corresponding to pre determined fluid amounts (eg an image of a "soaked" pad might be considered to be equal to 5mls). Women are asked to tally up how many of each they have experienced and a total estimated menstrual flow is calculated from that.

A pictorial assessment - such as comparing your flow to that of images of blood on a pad cannot be an accurate way to measure volume of blood lost, as the pads absorbency is designed to pull wetness from the top and may disguise the actual amount of blood lost…. Also different brands of disposable pad would presumably give different levels of absorption and have a different appearance, so it would only be accurate if the same type of pad is used by the woman as was used for the reference sample.

A link to a .pdf file showing a visual assessment chart for determining an estimate of menstrual flow

A website giving a non-visual assessment list for determining flow

3). Chemical tests (alkaline hematin) are done to measure the actual blood content found on the pads. By extracting the hemoglobin and comparing that to a sample taken from the woman in a blood test.

This website shows results of a study where menstrual loss was tested and found that around 50% of the total loss is actual blood. This would indicate that if a woman measures her loss at 200mls for the whole period, the "blood" loss would be around 100mls. This is quite important, as using the over 80mls=excessive volumes, if the flow is 200mls total volume/100mls blood it makes a huge difference.

This website also talks of a study done with the hemoglobin test, and says that their results were consistent with the 30mls average 80mls excessive measurements. Which when taken with the results from the above study (where total menstrual flow is around 50% "blood") would seem to indicate that these volumes given as averages, are based on actual blood lost, not of total flow volume.

An article on heavy periods, which mentions the hemoglobin test.

According to this website this 80mls is used as the indicator for heavy flow because it appears to be the maximum amount of blood loss that a woman on a normal diet can lose per cycle without becoming iron deficient. However it would seem that in most cases health care professionals will take the woman's judgement on whether it is "heavy" or not, without clarifying actual blood loss.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License