As if living with a chronic illness isn’t enough, adding smoking to the mix makes diabetes harder than ever to deal with. In short: don’t do it. The side effects of smoking if you are a type one diabetic are an increase in insulin resistance, making the synthetic insulin that diabetics use basically ineffective. If your body becomes insulin resistant due to smoking, there is really nothing that can be done. Insulin is the only known medicine that can treat diabetes; remember it is not a cure. Studies (http://care.diabetesjournals.org/cgi/content/full/25/4/796-a) show that diabetics who stopped smoking found themselves more in control of their blood sugar than those who did not stop smoking.
Remember the micro- and macrovascular complications of letting blood sugar levels go too high too often? Those diabetics who continue to smoke will become familiar with these complications earlier than those diabetics who are simply not in control. Smoking also increases the risk of heart disease (a macrovascular complication of diabetes without smoking).
In truth, the things that affect smokers affect diabetic smokers as well. The lack of oxygen, yellowing of teeth and nails, dental and gum problems, and circulation issues will hurt you before diabetes complications will. The catch is that diabetes basically speeds up these destructive processes (http://www.diabetesmonitor.com/b56.htm). So, if you want to live a long and healthy life (diabetic, or not), don’t smoke!