diff --git a/Environment-Variables.md b/Environment-Variables.md
index 11c1b09..bfed646 100644
--- a/Environment-Variables.md
+++ b/Environment-Variables.md
@@ -22,6 +22,7 @@ This page will list all environment variables that could be passed into Statping
 - `MAX_OPEN_CONN`             - Set [Maximum Open Connections](https://golang.org/pkg/database/sql/#DB.SetMaxOpenConns) for database server (default: 25)
 - `MAX_IDLE_CONN`             - Set [Maximum Idle Connections](https://golang.org/pkg/database/sql/#DB.SetMaxIdleConns) for database server (default: 25)
 - `MAX_LIFE_CONN`             - Set [Maximum Life Connections](https://golang.org/pkg/database/sql/#DB.SetConnMaxLifetime) for database server (default: 25)
+- `PREFIX` - Add a prefix string to each Prometheus metric (default is empty)
 
 ### Connection
 - `BASE_PATH`                 - Set the base URL prefix (set to 'monitor' if URL is domain.com/monitor)