If your doctor thinks you need more time off, why not take it? The time off will count towards your pension. That sounds like a good reason, but when you are feeling better, you may change your mind. Why not take as much time as you need to recover? I think your pension will be reduced to about 80% of of your 25 years if you retire at 55 but check on the Teachers' Pensions website. Perhaps the important question is whether you can afford to take ARB and whether you need the additional amount you would get if you were able to get ill-health retirement.