The 22-year-old will be available for Quins’ Gallagher Premiership home fixture with Leicester Tigers at the end of the month, before heading back to Gloucester for the return of the league in March.
The 6’7″ former England U20 international has made ten appearances for Gloucester so far this season, with five of those coming in the Premiership.
Before their fixture against Leicester, Harlequins will host Ulster this Saturday in the Investec Champions Cup, where they will be striving for a home tie in the round of 16, having already qualified for the knockouts.
Lamb missed out on Italy’s Guinness Six Nations squad yesterday due to an injury picked up in December. Harlequins director of rugby Billy Millard confirmed at the beginning of the month that both Lamb and Lewies are seeing specialists.