The 21-year-old defender joined the League One club on an initial month-long deal back in January.
Garmston has made seven appearances during his time with the Gills.
The full-back scored his first professional goal during Saturday's 4-2 victory over MK Dons.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Leeds UnitedLeeds | 37 | 23 | 10 | 4 | 74 | 23 | 51 | 79 |
| 2 | Sheffield UnitedSheff Utd | 37 | 24 | 7 | 6 | 52 | 28 | 24 | 77 |
| 3 | Burnley | 37 | 20 | 15 | 2 | 50 | 11 | 39 | 75 |
| 4 | Sunderland | 37 | 19 | 12 | 6 | 55 | 34 | 21 | 69 |
| 5 | West Bromwich AlbionWest Brom | 37 | 13 | 17 | 7 | 47 | 33 | 14 | 56 |
| 6 | Coventry CityCoventry | 37 | 16 | 8 | 13 | 52 | 48 | 4 | 56 |
| 7 | Bristol City | 37 | 13 | 15 | 9 | 47 | 40 | 7 | 54 |
| 8 | Middlesbrough | 37 | 15 | 8 | 14 | 57 | 48 | 9 | 53 |
| 9 | Blackburn RoversBlackburn | 37 | 15 | 7 | 15 | 41 | 38 | 3 | 52 |
| 10 | Watford | 37 | 15 | 7 | 15 | 47 | 50 | -3 | 52 |
| 11 | Sheffield WednesdaySheff Weds | 37 | 14 | 9 | 14 | 53 | 58 | -5 | 51 |
| 12 | Norwich CityNorwich | 37 | 12 | 13 | 12 | 59 | 52 | 7 | 49 |
| 13 | Millwall | 37 | 12 | 12 | 13 | 36 | 39 | -3 | 48 |
| 14 | Queens Park RangersQPR | 37 | 11 | 11 | 15 | 42 | 48 | -6 | 44 |
| 15 | Preston North EndPreston | 37 | 9 | 17 | 11 | 37 | 43 | -6 | 44 |
| 16 | Swansea CitySwansea | 37 | 12 | 8 | 17 | 38 | 47 | -9 | 44 |
| 17 | Portsmouth | 37 | 11 | 9 | 17 | 45 | 59 | -14 | 42 |
| 18 | Hull City | 37 | 10 | 10 | 17 | 38 | 46 | -8 | 40 |
| 19 | Stoke CityStoke | 37 | 9 | 12 | 16 | 37 | 50 | -13 | 39 |
| 20 | Oxford UnitedOxford Utd | 37 | 9 | 12 | 16 | 38 | 55 | -17 | 39 |
| 21 | Cardiff CityCardiff | 37 | 8 | 12 | 17 | 40 | 61 | -21 | 36 |
| 22 | Derby CountyDerby | 37 | 9 | 8 | 20 | 37 | 49 | -12 | 35 |
| 23 | Luton TownLuton | 37 | 9 | 7 | 21 | 34 | 60 | -26 | 34 |
| 24 | Plymouth ArgylePlymouth | 37 | 7 | 12 | 18 | 38 | 74 | -36 | 33 |
| > Championship Full Table | |||||||||
