The Visible Infrared Imaging Radiometer Suite (VIIRS) on the S-NPP satellite has been in successful operation for more than six years. One of the key performance parameters of the instrument detectors is the saturation of their digital counts (DN). For VIIRS, when the scene spectral radiance level is high enough, before reaching the digital maximum that can be accommodated by the number of bits, the DN for the detector stops increasing and often decreases with increasing scene radiance. Consequently, for some high scene radiances, the pixel spectral radiance calculated from the DN does not accurately reflect the true radiance. To inform the data product user that the calculated pixel radiance may not be accurate, a quality flag is used to indicate that the pixel may be inaccurate. In the current S-NPP VIIRS L1B product, the DN saturation flag is turned on once the DN exceeds a fixed threshold level. In this study, the VIIRS Reflective Solar Band (RSB) detectors’ true threshold levels are characterized by studying their responses to high radiance scenes. The long-term trending of these true threshold levels for each detector is analyzed to examine whether the threshold levels are time dependent. Some saturation effects that may be amenable to correction are also investigated, resulting in more useful data. The results from this study will improve data quality with more accurate DN saturation flags.