Yes, you can do this. In hindsight, I should've moved up to 3.75 mg and stayed there rather than what I thought I was doing (moving up to 5 mg over a few weeks but found that I couldn't tolerate anything above 4.2 mg for quite a long time).
Here are all the doses I have taken so far (in mg) - I used a 1 ml syringe for all the 'non standard' doses.
Pen 1 (2.5 mg) - 2.5, 2.5, 2.5, 2.5, 3.2
Pen 2 (5.0 mg) - 4.2, 4.2, 4.6, 2.5, 4.2
Pen 3 (5.0 mg) - 4.2, 4.4, 3.3, 3.75, 3.75
Pen 4 (5.0 mg) - 3.75, 4.2, 4.2, 4.2, 4.2
Pen 5 (5.0 mg) - 4.2, 4.5, 4.6, 4.6, 4.6
Pen 6 (5.0 mg) - 4.6, 5.0, 5.0, 5.0, 5.0
Pen 7 (5.0 mg) - 5.8, 5.8, 6.3, 6.7
Pen 8 (7.5 mg) - 6.9, 7.5, 7.5, 8.1, 8.8
Pen 9 (7.5 mg) - 9.5, 10.0, 10.0, 10.0
Pen 10 (10.0 mg) - 10.0
Pen 11 (12.5 mg) -