Method to determine LD50 using alamarBlue®

alamarBlue® protocol:

Method to determine LD50 using alamarBlue

alamarBlue can be used to determine the median lethal dose LD50 value and similar assays testing the effects of a toxin, radiation, or pathogen against cell cultures.

Percentage difference in reduction (equation 5)


A LW  - ( A HW  R O ) for test well  

A LW  - ( A HW  R O ) for control well



Use semi-log graph paper to plot the percent of untreated control (using equation 5) for each dilution of a given test agent on the y-axis vs. the concentration of the test agent on the x-axis. 

To determine the LD50 endpoint from the graph, read from where the 50 percent point intercepts the Dose. 


Response Curve to the concentration along the x-axis. This concentration is the LD50 value.