VBA Hiding rows

Hey does anyone know how I can make the following code more efficient, it seems to take a really long time to do this, the code hides the row if there is no data in the coloumn, it does it for 3 different sections:

LastRow = Range("B65000").End(xlUp).Row
For I = LastRow To 47 Step -1
If Cells(I, "I") = "" Then
Rows(I).Hidden = True
End If
Next I

LastRow = Range("B65000").End(xlUp).Row
For I = LastRow To 815 Step -1
If WorksheetFunction.IsText(Cells(I, "I")) Then GoTo nexti
If Abs(Cells(I, "I").Value) < 1 And Abs(Cells(I, "L").Value) < 1 Then
Rows(I).Hidden = True
nexti:
End If
Next I

LastRow = Range("A65000").End(xlUp).Row
For I = LastRow To 1387 Step -1
If Cells(I, "A") = "" Then
Rows(I).Hidden = True
End If
Next I