The serious complications than can occur in smokers with diabetes may be caused by nicotine, research suggests.
A study has found a link between the addiction-causing chemical and continuous raised blood sugar levels experienced by people with diabetes.
Scientists have warned that the danger means people with diabetes should “make every effort” to give up smoking.
People with diabetes trying to quit the habit who are using nicotine-replacement therapy over long periods could also face complications.
In the UK, just under three million people are diagnosed with diabetes, but almost a million more could have the condition without being aware of it.
The disease can lead to complications including potentially life-threatening heart attacks, strokes, kidney failure and nerve damage.
These serious complications usually result from out of control blood sugar levels, which cause destruction on the body. To avoid this from happening, the blood sugar needs to be managed correctly.
Doctors have long known that smoking increases the risk of diabetic complications, but it has not been clear what tobacco substances are to blame.
The new research, reported at the 241st national meeting of the American Chemical Society in Anaheim, California, points to the prime suspect being nicotine.
Using human blood samples, the scientists showed that nicotine concentrations typical of those in smokers appeared to raise long-term blood sugar levels in diabetics.
Dr Xiao-Chuan Liu, from California State Polytechnic University in Pomona, who led the study said the benefits of quitting probably meant people with diabetes should not avoid using nicotine patches and similar products for short periods of time.
However, the research raised concerns about the long-term use of nicotine replacement therapy.
Have you signed our petition to ensure nurses have a seat on consortia boards? Follow @Aseatontheboard on twitter follow for all the latest campaign news!