Coltman has been called in to cover Asafo Aumua, who is recovering from a head knock sustained while playing for Wellington.
Coltman scored a try in the Ranfurly Shield win over Taranaki after a strong performance in a Mitre 10 Cup match against Manawatu.
The news comes as uncapped Crusaders lock Mitchell Dunshea has also been called into the squad.
Dunshea replaces Crusaders teammate Quinten Strange, who has left the camp with an ankle injury.
Strange is understood to be sidelined for six to eight weeks, effectively ruling him out of the upcoming Bledisloe Cup and Rugby Championship.
His departure leaves the squad with a gap in an already tricky area of depth. Dunshea will assemble with the team next week in Wellington ahead of the first Bledisloe Cup test.
Hurricanes midfielder Ngani Laumape and Crusaders captain Scott Barrett have also joined the camp.
Laumape (broken forearm) and Barrett (toe) will have their respective injuries assessed but both are expected to be among the 11 players added to the original 35-man squad, along with Wellington midfielder Peter Umaga-Jensen, who is in line to replace the injured Braydon Ennor, for the Rugby Championship.