The Mansfield-Voda-Jorgensen Menstrual Bleeding Scale is often used to rate the amount of flow you have – although it could be said that this method of derermining blood flow is quite subjective. It is also done using standard disposable products, which do vary greatly in absorbency. I would assume they are using the standard regular absorbency pads rather than anything super absorbent. (cloth pads are likely to be more absorbent than disposables). The ratings are listed as:
“Spotting” – A drop or two of blood, not even requiring sanitary protection, though you may prefer to use some.
“Very Light Bleeding” – Needing to change a low-absorbency tampon or pad one or two times per day, though you may prefer to change them more frequently.
“Light Bleeding” – Needing to change a low- or regular-absorbency tampon or pad two or three times per day, though you may prefer to change more frequently.
“Moderate Bleeding” – Needing to change a regular-absorbency tampon or pad every three to four hours, though you may prefer to change more frequently.
“Heavy Bleeding” – Needing to change a high-absorbency tampon or pad every three to four hours, though you may prefer to change more frequently.
“Very Heavy Bleeding or Gushing” – Protection hardly works at all; you would need to change the highest absorbency tampon or pad every hour or two.
Measuring the actual amount of menstrual loss can also be done by one of 3 ways:
- Weighing pads. An unused pad/tampon is weighed to determine the starting weight, and then all used pads/tampons are weighed. The weights are added up and the weight of the unused products subtracted and the remaining weight is that of menstrual flow.
- Using images of disposable pads rated from “spotting” to “soaked” 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 10mls). The number of mls is then estimated from the number of corresponding pads the woman has used.
- Chemical tests (alkaline hematin) are done to measure the actual blood content found on the pads/tampons.
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.
A pictorial assessment – such as comparing your flow to that of images of blood on a pad like this chart, 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….
I know that I’ve looked at the top of a pocket style pad and then been surprised at the amount of blood on the inserts inside it, as they held more blood than I’d imagined. If a sample pad is used and certain volumes of liquid poured onto it as the method of determining how much volume the pads equate to (which is how I assume they calculate those pictorial tests)…. different brands of disposable pad would presumably give different levels of absorption and have a different appearance, so it would only be remotely accurate if the same type of pad is used by the person as was used for the sample.
Only a chemical test can determine the amount of actual “blood” in a sample, where other measurements, particularly simply weighing the pad, can take other fluids into account, such as sweat and other vaginal secretions.