Does smoking cause diabetes?
Smoking is linked to type 2: smokers are about a third more likely to get it. With diabetes, smoking can double your risk of complications. Quitting wins, though risk can rise for a few years.
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Does smoking cause diabetes?
Smoking is strongly linked to type 2 diabetes. A review of 88 studies with almost 6 million people found smokers were 37% more likely to get it than non-smokers. That’s about a third.
These studies watch people over time. They can’t fully prove that smoking is the cause. But the link held in every group the authors checked, and an earlier review of 1.2 million people found much the same.
Think of it like a weather forecast. A higher chance of rain doesn’t mean it will rain on you. It does mean more people get wet.
| Who | Extra risk | Compared with |
|---|---|---|
| Smokers | 37% more likely | People who don’t smoke |
| Ex-smokers, overall | 14% more likely | People who never smoked |
| Never smoked, but around other people’s smoke | 22% more likely | Never smokers not around smoke |
Smoke now? Ask your local Stop Smoking Service for free help to stop. Ex-smoker? Your risk falls the longer you stay quit, though it can rise for the first few years, mainly if you gain weight.
Does the number of cigarettes matter?
Yes. In the same review, the more people smoked, the higher their risk of type 2.
| Cigarettes a day | Extra risk | Compared with |
|---|---|---|
| Fewer than 10 | 21% more likely | People who never smoked |
| 10 to 19 | 34% more likely | People who never smoked |
| 20 or more | 57% more likely | People who never smoked |
Sources: Pan et al 2015; Pan et al 2015, full text
So cutting down is better than nothing. But even fewer than 10 a day still carried a higher risk than never smoking. Stopping is the goal.
Does quitting smoking lower diabetes risk?
Yes, over time. The NHS says people who quit are less likely to develop type 2 diabetes. Pan’s review found the risk falls a lot the longer you stay quit.
Diabetes risk after quitting, compared with never smokers
- 1
First 5 years
54% more likely to get type 2.
- 2
5 to 9 years
18% more likely.
- 3
10 years or more
11% more likely.
Source: Pan et al 2015
Look at the first step: 54%, higher than the 37% for people who still smoke. That’s the early rise, and it has a cause you can plan for, explained next. Already quit? Keep going: by 10 years the extra risk is down to 11%.
Why can quitting raise your risk at first?
That rise seems to come from weight gain. Nicotine dulls your appetite, so you may feel hungrier after you stop. Most people gain some weight.
A large US study followed people who quit. Their risk of type 2 was 22% higher than smokers’ 2 to 6 years later, and peaked at 5 to 7 years. The rise matched how much weight they gained. People who didn’t gain weight had no rise.
| Weight gained after quitting | Death from heart and blood vessel disease |
|---|---|
| None | 31% lower than smokers |
| Up to 5 kg | 53% lower than smokers |
| 5 to 10 kg | 75% lower than smokers |
| More than 10 kg | 67% lower than smokers |
Source: Hu et al, NEJM 2018
So don’t keep smoking to stay slim. The NHS says the benefits of quitting are far greater than the risks of gaining some weight. Just plan for the hunger.
Five ways to quit and keep weight gain down
- Contact your local Stop Smoking Service. It’s free, and expert help makes you 3 times more likely to quit for good.
- Pair a slow source of nicotine, like a patch, with a fast one, like a mouth spray or vape. Your Stop Smoking Service adviser can help you choose products that suit you.
- Plan balanced meals with fruit, vegetables and wholegrains, because your appetite may rise.
- Walk when a craving hits. Gentle activity can help you stay fit and cut cravings.
- If you have diabetes, tell your diabetes team you smoke, so they can help you stop.
Sources: NHS: find a Stop Smoking Service; NHS: nicotine withdrawal; NHS: what could happen when you quit; Diabetes UK
Weighing up a vape or patches? See vaping to quit smoking and nicotine patches.
What does smoking do if you have diabetes?
Diabetes already raises your chance of a heart attack, stroke or poor blood flow in your legs. Diabetes UK says smoking can double your risk of complications on top of that.
Type 2 can also harm your feet, eyes, kidneys and gums. The NHS says you can lower the chance of these by managing your blood sugar, eating well, exercising and not smoking.
Your team will ask if you smoke at your annual review. Say yes, and ask for support. Diabetes UK says you’re more likely to quit with the right help.
To track your blood sugar over time, see the HbA1c blood test.
When to speak to a GP
Not everyone with type 2 diabetes has symptoms, so a blood test is how it’s found. See a GP if:
- You feel very tired, pee more than usual, feel thirsty all the time or lose weight without trying. Blurred vision, slow-healing cuts, genital itching or repeated thrush can also be signs.
- You have a higher risk of type 2, such as a parent, brother or sister with it, or being overweight and not very active.
- You have diabetes and get blisters or cracked skin on your feet, or your vision gets worse.
- You have diabetes and get pain, tingling or numbness, problems having sex, constipation or diarrhoea. These could be signs of nerve damage.
Call 999 or go to A&E if you have type 2 diabetes and are peeing a lot, feel very thirsty, feel sick, feel confused, very sleepy or drowsy, or get short of breath. These could be signs of a life-threatening blood sugar emergency.
Aged 40 to 74 with no existing condition? Ask your GP surgery or pharmacy for a free NHS Health Check. See also prediabetes and the diabetes blood test.