The Government is being warned that the homelessness crisis is contributing to the country's drug problems.
Merchants Quay Ireland says it is much harder for an addict to get clean without a roof over their head.
The President Michael D Higgins will visit the charity's base in Dublin today as they unveil their annual review.
The latest statistics show more than a thousand people used their GP services last year - an increase of more than a quarter.
Merchants Quay CEO, Tony Geoghegan, says the housing shortage is having a knock-on effect on rehab efforts.
He said: "It's impossible for people to get themselves together and to attempt to engage in treatment meaningfully if they don’t know where they are going to sleep at night.
"Even in the emergency accommodation, the bulk of that is done on a one-night only basis.
"Someone rings up today, gets their bed for tonight, but aren't assured of their bed until the next night when they have to ring again."