Date Published

March 18, 2020

Updated For

ALS PCS Version 5.2


Having trouble looking at external blood loss and coming up with an accurate number to communicate at transfer of care? Here is a great way to assess and estimate small amount of blood loss.

MAR Method

The MAR method was created by MERLIN, ALTER and RAFFEL in response to the overwhelming inaccuracy and inconsistency of health care provider’s estimation of external blood loss.

Note that this assessment tool has yet to be validated in any clinical setting.  Therefore, it cannot be used as a specific finding or value, and can aid in estimation of blood loss (a lot vs. a little)

Remember, when considering a potential trauma bypass, external blood loss is not listed in any of the specific assessment criteria. The Field Trauma Triage Standard (FTTS) should be utilized in all traumatic events and can be found here for further review.  Hyperlink à FTTS

How to Position Your Hand


  • The fist should be held at a height of 5cm (2.5 inches) from the blood surface.


  • The anterior surface of the fist should point towards blood


  • There should not be any gap between fists while measuring.


  • The Metacarpal pharyngeal joints should not point down while measuring.


1 Hand = 20ml of blood

Remember that this estimation may be valuable for small amount of external blood loss but also highlights the importance of PPE and safety.


Estimation of Blood Loss

Estimation of Blood Loss

Reference: External blood loss estimation using the MAR Method.

Merlin MA, Alter SM, Raffel B, Pryor PW 2nd.

Am J Emerg Med. 2009 Nov;27(9):1085-90. doi: 10.1016/j.ajem.2008.07.039.



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