The global population size of the Purple-throated Mountain-gem has not been estimated (BirdLife International 2011). It has a small distribution, and the population is believed to be in decline. Nevertheless the conservation status of the Purple-throated Mountain-gem is rated as Least Concern (BirdLife International 2011). As is true of all hummingbirds (regardless of rarity), it is included in Appendix II of CITES.
The relative abundance of the Purple-throated Mountain-gem is assessed as "common to locally abundant" in Costa Rica (Stiles and Skutch 1989).
Effects of human activity on populations
The Purple-throated Mountain-gem is not threatened but is thought to be declining due to continuing deforestation (Schuchmann 1999). Small-scale disturbances in the highlands of Costa Rica and Panama due to human development have altered the habitat of this species, although vast expanses of cloud forests within their range remain beyond human influence (Feinsinger et al. 1987). Studies in the Monteverde Cloud Forest Reserve of Costa Rica revealed that the Purple-throated Mountain-gem is very successful in areas with patchy deforestation, including large clearings due to human influence and treefalls inflicted by natural mudslides (Feinsinger et al. 1987, Feinsinger et al. 1988). Although these disturbances introduce increased competition from other hummingbird species, these studies attest to the strong resiliency of Purple-throated Mountain-gem populations in the face of habitat alteration.