Err, yeah bg readings of 10 -13 are over double what is normal for your body, so you're bound to feel pretty rubbish. Tiredness and general lethargy are quite common in this situation, but will vary in degree from one person to another. The only thing to do is not let them get that high, and try to keep them below 7 as much as you can. If you're used to having bg in the 10-13 range, reduce slowly otherwise you may feel hypo even though you're not, this is just because your body has become accustomed to the previously high levels. If you still feel tired after getting your levels back to normal, go see your GP.