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Tobacco and diabetes

Scientific support: PD Dr. Martin Füchtenbusch

What do cigarettes have to do with diabetes? They are one of the lesser known – but among the most significant – risk factors for developing type 2 diabetes. It is estimated that 25 million cases of diabetes worldwide can be attributed to cigarettes.

Several major studies have now confirmed that active or passive smokers are more at risk of developing type 2 diabetes. It is not completely clear why, although some reasons have been established.

1. How does smoking affect blood glucose levels?

The nicotine in tobacco affects the glucose level in several ways. People who smoke have a higher blood glucose level than those who do not. If blood glucose is persistently elevated, you are more likely to develop type 2 diabetes in the long-term.

For more information on the development of type 2 diabetes, visit our Living with Diabetes portal!

Insulin production

Insulin release appears to be different in smokers. Insulin, a hormone produced by the body, is important as it stops blood glucose rising in an uncontrolled manner. It acts as a kind of door opener, ensuring that sugar that enters the blood after a meal actually gets to the cells that need it.

Nicotine appears to slow down production of this important substance, by inhibiting work in the “insulin factories” in the pancreas known as the beta cells.

Insulin effect

Various chemicals in cigarettes and other products containing nicotine also lead to more inflammation in the body. This means that insulin cannot reach its target cells as easily, because cells that are inflamed often do not respond as readily to hormones, messenger substances and other substances in the body and so more insulin is needed for organs like the brain and liver and for the muscles to absorb sugar from the blood.


Elevated levels of the toxin arsenic have also been found in the blood of smokers. These can also contribute to a higher level of blood glucose. Another toxin found in some tobaccos is cadmium. This heavy metal can lead to weight gain and an insulin deficiency in the body.

Fat in the organs

Another reason why smokers are at a higher risk of diabetes is surprising at first glance: Body fat. Although smokers are often relatively slim, the fat they do have is often especially harmful. Because not all fats are alike. There is body fat that tends to be harmless: known as subcutaneous fatty tissue. And there is fat that wraps around the internal organs, such as the liver, kidneys and intestines and which, if it gets the upper hand, releases a problematic mix of messenger substances and fatty acids into the blood, thereby increasing the risk of diabetes and cardiovascular disease.

Fat deposits within organs are especially harmful, as is the case with fatty liver disease because this fat makes it more difficult for the liver to do its job. And this means that it can no longer properly manage one of its most important tasks - controlling blood sugar levels. Smoking can make it more likely that a person will develop non-alcoholic fatty liver disease.

2. How high is the risk of type 2 diabetes as a result of smoking?

To what extent smoking increases the risk of diabetes depends on how many cigarettes you smoke a day and over how many years. This is why the figures in the studies vary. Some estimate a 30 to 40 percent higher risk. Others estimate that smoking doubles the risk of diabetes. This means that under the same conditions, out of 1,000 non-smokers, about 100 people will at some point in their life develop type 2 diabetes. And out of 1,000 smokers, the estimates in one study are that 130 to 140 people will develop diabetes and as many as 200 people in the other study.

Especially risky: Smoking in pregnancy

Smoking in and even before pregnancy increases, among many other risks, the risk of the expectant mother developing gestational diabetes. The risk for the unborn child of developing diabetes in later life also increases. The children of mothers who smoke are also often smaller at birth.

Does the risk of diabetes increase with passive smoking?

Many people - especially children - do not actually smoke, but are exposed to cigarette smoke through what is called passive smoking. The smoke has an effect on their health. This especially applies to people who were exposed to smoke as children or young adults. They are much more likely to develop type 2 diabetes than people who do not smoke and were not exposed to passive smoke. The risk of diabetes increases, the more people around you smoke. Someone frequently exposed to passive smoke is at a greater risk of developing diabetes that someone who only occasionally sits next to someone who smokes.

3. E-cigarettes: How does smoke affect the risk of diabetes?

E-cigarettes are filled with liquid that is turned into steam in the e-cigarettes. This steam is inhaled. The liquids, also called e-liquids or e-juice, contain substances that are smoked. This may be nicotine, essential oils or other substances. There are more than 7000 different flavors on the market made up of these substances. Many of these liquids contain sugar. When it is heated in the e-cigarette, these can be converted into harmful substances, such as carcinogenic formaldehyde.

There are hardly any scientific studies for many of these liquids. Most studies to date have focused on the risk of cancer or cardiovascular disease. Long-term studies on e-cigarettes and other evaporators on the risk of diabetes have still not been conducted as they have not yet been on the market for long. It is, however, already known that liquids with and without nicotine increase the risk of diabetes.

4. What can be done?

Nicotine is one of the most addictive substances which is why it is so hard to give up smoking. It helps to have a clear picture of how beneficial it is for you yourself and your health to give up smoking:

  • It increases your own chances of staying healthy and fitter for longer.
  • It lowers your risk of lung cancer, heart attack, stroke and type 2 diabetes and helps your skin and teeth.
  • And it leaves you with more time and money in your pocket.

Once they have decided to give up, some smokers successfully quit on their own without any help. But nobody has to give up smoking on their own. There are many seminars and stop-smoking programs. The German Cancer Research Center, in collaboration with the Federal Center of Health Education (BZgA) offers a Find providers in your area (Link in German).

Self-help groups and internet portals such as or (Websites in German) give non-smokers-to-be the chance to get in touch with like-minded people and to share their stories.

If you need advice on preparing to give up smoking and the process itself, and any information on the various methods you can use to support you, the information portal from the Federal Center for Health Education (BZgA) has a wide range of information, including an online quit smoking program (Websites in German).

And what if you put on weight when you give up smoking?

Many people who give up smoking initially put on weight. This could be because the risk of diabetes often does not fall immediately after you stop smoking, but rather even temporarily increases and it takes time for it to fall to much lower than it originally was. This can probably be avoided by keeping your weight at least roughly the same. In studies, people who do not gain weight when they stop smoking had a lower risk of diabetes.

How high the risk of diabetes is after quitting smoking depends on how much you used to smoke before. People who used to be heavy smokers still have a higher risk of diabetes after giving up smoking than people who only smoked a little.

Over time, giving up tobacco certainly does reduce the risk of diabetes. It takes about 5 to 10 years for it to fall to the same level as a non-smoker.

Good to know:

In studies, “heavy smoker or very heavy smoker” tends to be defined as smoking at least 20 cigarettes a day. Some studies also use a parameter called pack years. Pack years are calculated based on the number of cigarettes smoked per day or cigarette packs and the number of years of smoking.

Pack years = (smoked cigarette packs per day OR smoked cigarettes per day/20) x (years of smoking)

At least 14 pack years is considered “heavy smoker or very heavy smoker”.

5. How does smoking affect you if you already have diabetes?

Smoking is a major risk factor, especially for people who already have type 1 or type 2 diabetes. Nicotine from cigarettes can accelerate complications because nicotine constricts the blood vessels and nerve pathways and slows down wound healing. For example, smokers are more likely to have diabetic foot syndrome than someone who does not smoke or vape. People with diabetes are also more likely to develop eye problems if they smoke. This can lead to a higher rate of blindness in smokers with diabetes than in non-smokers with diabetes. Having diabetes already places a great deal of strain on the cardiovascular system and the kidneys. The blood vessels in the heart and kidneys are subject to further damage as a result of smoking. They could have a heart attack or kidney disease (diabetic nephropathy) sooner. So it is worth seeking help to quit smoking – also because the family also tends to be exposed to passive smoke.


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As of: 12.12.2022